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Sweet Corn IPM Newsletter No. 10 – August 29, 2014

Sweet Corn IPM Newsletter No. 10 – August 29, 2014

Click on photos to enlarge.

PEST PRESSURE MODERATE IN MOST LOCATIONS

Highest Threat Remains in Most Southern and Coastal Regions

SITUATION
A brief warm spell pushed late season corn development this week, but more cool weather on the way should slow growth and pest pressure over the next few days. Crop quality continues to be very good, and insect pressure continues to be fairly moderate as we begin to wrap up another corn season. Next week’s newsletter will be the last issue planned for this season.

European corn borer: Most trapping sites caught corn borer moths this week, but numbers vary greatly by location. These moths will continue to threaten any fresh silking corn remaining in fields that are not on a spray schedule for corn earworm. Farmington, New Gloucester, Nobleboro, Oxford, Poland Spring, Sabattus, Wales and Warren were over the threshold of 5 moths per week in silking corn. The New Gloucester, Oxford, Poland Spring and Sabattus sites were not on spray regimes for corn earworm, so silk sprays were recommended. European corn borer feeding damage in pre-tassel corn was not over the 15% threshold in the few locations with young corn remaining.

Corn earworm: Corn earworm moth counts were lower in most sites this week. Cool evening weather will probably keep activity low over the next few days. A 4-day spray interval was recommended for corn earworm on silking fields in Cape Elizabeth and one Lewiston site. A 5-day spray interval was recommended in Levant, Wales, Warren and one Dayton site. A 6-day spray interval was recommended in Charleston, Nobleboro and Palmyra.

Fall armyworm: Moth captures were erratic this week; with many sites catching no moths while others had very high counts. Feeding damage from larvae was also not as prevalent this week, although there are only a few fields left that are not yet in silk. Fields in Cape Elizabeth, Dayton, Monmouth, New Gloucester, Nobleboro, and Wales exceeded the threshold of 3 moths per week in silking corn. However, only the Monmouth and New Gloucester sites were not on a spray regime for corn earworm. Fall armyworm feeding damage did not exceed the 15% threshold in any of the sites with pre-silking corn remaining.

Corn Rust: We found several fields showing symptoms of corn rust this week. This fungus disease causes reddish-brown pustules to form on the leaves, stalks and husks. When the spores get spread over the husks, it can diminish the visual quality of the ears. A fungicide spray for rust is only recommended when infection occurs prior to tassel. Later infections are unlikely to cause enough damage to justify control measures.

When Should You Stop Spraying?
When a silking cornfield is under a recommended spray interval for corn earworm, spraying may be stopped once the silks have become thoroughly dried and brown. However, if earworm pressure is very high (e.g. 91+ moths/week) and/or fall armyworm moths are over threshold (3+ moths per week), then spraying should continue until either the moth counts drop, or you reach the required days before harvest (dh) for the product being used.

Sincerely,

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management Office
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259          Orono, ME 04473
207.933.2100                           1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Moths
ECB
Moths
FAW
Moths
%Feeding
Damage
Recommendations / Comments
Bowdoinham 1 0 1 13% No spray recommended
Cape Elizabeth I 21 0 0 1 4-day spray interval recommended on all silking corn
Cape Elizabeth II 70 2 30 4-day spray interval recommended on all silking corn
Charleston 3 1 0 6-day spray interval recommended on all silking corn
Corinth 2 0 0 0% 6-day spray interval recommended on all silking corn
Dayton 4 2 3 2% 5-day spray interval recommended on all silking corn
Farmington 0 9 0 One spray recommended for ECB on silking corn
Levant 7 1 0 0% 5-day spray interval recommended on all silking corn
Lewiston I 1 1 0 8% No spray recommended
Lewiston II 13 0 0 4-day spray interval recommended on all silking corn
Monmouth 0 2 12 One spray recommended for FAW on silking corn
New Gloucester 1 5 21 12% One spray recommended for ECB+FAW on silking corn
Nobleboro 3 11 4 6-day spray interval recommended on all silking corn
Oxford 0 6 0 One spray recommended for ECB on silking corn
Palmyra 3 3 0 6-day spray interval recommended on all silking corn
Poland Spring 1 8 0 One spray recommended for ECB on silking corn
Sabattus 0 28 0 One spray recommended for ECB on silking corn
Wales 6 5 4 5-day spray interval recommended on all silking corn
Warren 7 13 2 5-day spray interval recommended on all silking corn
Wayne 0 0 1 6% No spray recommended
Wells I 0 0 0 1% No spray recommended
Wells II 1 1 2 0% No spray recommended

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm

Corn Earworm Spray Thresholds for Pheromone Traps

Moths caught per week Moths caught per night Spray interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every 6 days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every 3 days

Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.

European Corn Borer Thresholds
Whorl stage: 30% or more of plants scouted show injury.
Pre-tassel-silk: 15% or more of plants scouted show injury.
Silk: 5 or more moths caught in pheromone traps in one week.

IPM Web Pages:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

The University of Maine is an equal opportunity/affirmative action institution.

Image Description: Sweet Corn

Image Description: European Corn Borer Larva on Ear

Image Description: Rust on Corn

Sweet Corn IPM Newsletter No. 9 – August 22, 2014

Sweet Corn IPM Newsletter No. 9 – August 22, 2014

Click on photos to enlarge.

CORN EARWORM NUMBERS INCREASING

Highest Threat in Southern Coastal Region

SITUATION
Cooler days and nights have slowed later corn development, but supply and quality still seems to be good. There has been a significant increase in pest activity, but for the moment it is fairly localized in the southern coastal region.

European corn borer: We continue to catch moths in most locations. Although, with the exception of our Sabattus site, the counts are fairly low. It appears that a second generation of corn borer is underway, which could threaten silking corn in fields that are not on a spray schedule for corn earworm. Biddeford, North Berwick, Sabattus, and Warren were over the threshold of 5 moths per week in silking corn. Only the North Berwick site was not also on a spray regime for corn earworm, so a spray was recommended there. European corn borer feeding damage in pre-tassel corn was over the 15% threshold in North Berwick, Biddeford, Cape Elizabeth, Poland Spring and Wayne this week.

Corn earworm: Corn earworm moth counts jumped higher in some sites this week, most notably in the southern coastal region. A 4-day spray interval was recommended for corn earworm on silking fields in Biddeford, Cape Elizabeth, Garland, Wales and one Wells site. A 5-day spray interval was recommended in Monmouth and one Dayton site. A 6-day spray interval was recommended in Farmington, Levant, one Lewiston site, Sabattus, Warren and Wayne.

Fall armyworm: Most trapping sites had few, if any moths this week, although feeding damage from larvae has increased in some fields. Fields in Biddeford, Cape Elizabeth, Farmington, Monmouth, Nobleboro, and one Wells site exceeded the threshold of 3 moths per week in silking corn. However, only the Nobleboro site was not on a spray regime for corn earworm. Fall armyworm feeding damage on plants exceeded the 15% damage threshold alone, or in combination with European corn borer feeding, in Biddeford, Dayton and Warren this week.

Corn leaf aphids may infest corn plants in fields that have not recently been sprayed for other pests. Colonies of these small, bluish-green insects can nearly cover the tassels, stalks and husks. The waste aphids excrete on the plants, called “honeydew” stimulates the development of sooty mold fungus. This dark, slimy fungus can coat the surface of the husks, greatly reducing the visual appearance of the ears. Sprays applied for corn earworm will usually also control aphids. A spray for aphids would only be recommended if sooty mold is becoming a problem.

Pesticide disposal: This October, the Maine Board of Pesticides Control (BPC) and the Maine Department of Environmental Protection will offer free disposal of banned or unusable pesticides. Collection will occur at sites located in Presque Isle, Bangor, Augusta and Portland. To qualify, people must register by September 26, 2014. Registration is mandatory; drop-ins will not be permitted. To register or get details and important information about the temporary storage and transportation of obsolete pesticides, go to the BPC web site at http://www.thinkfirstspraylast.org and click on Obsolete Pesticide Collection, or call 207-287-2731.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management Office
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259          Orono, ME 04473
207.933.2100                           1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Moths
ECB
Moths
FAW
Moths
%Feeding
Damage
Recommendations / Comments
Biddeford 35 5 3 36% 4-day spray interval recommended on all silking corn
Cape Elizabeth I 72 4 0 4-day spray interval recommended on all silking corn
Cape Elizabeth II 67 4 9 29% 4-day spray interval recommended on all silking corn
Charleston 0 1 0 No spray recommended
Dayton I 0 0 0 No spray recommended
Dayton II 4 3 0 29% 5-day spray interval recommended on all silking corn
Farmington 2 1 4 6-day spray interval recommended on all silking corn
Garland 9 0 0 1% 4-day spray interval recommended on all silking corn
Levant 2 0 0 2% 6-day spray interval recommended on all silking corn
Lewiston I 2 3 0 6-day spray interval recommended on all silking corn
Lewiston II 0 4 0 7% No spray recommended
Monmouth 5 3 10 0% 5-day spray interval recommended on all silking corn
Nobleboro 0 2 4 One spray recommended for FAW on silking corn
No. Berwick 0 6 1 25% One spray recommended for ECB on silking corn
Oxford 0 2 0 3% No spray recommended
Palmyra 0 0 0 No spray recommended
Poland Spring 0 0 0 6% No spray recommended
Sabattus 3 29 0 6-day spray interval recommended on all silking corn
Wales 11 1 1 4-day spray interval recommended on all silking corn
Warren 2 10 2 37% 6-day spray interval recommended on all silking corn
Wayne 3 1 0 27% 6-day spray interval recommended on all silking corn
Wells I 1 0 1 0% No spray recommended
Wells II 15 3 4 11% 4-day spray interval recommended on all silking corn

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm

Corn Earworm Spray Thresholds for Pheromone Traps

Moths caught per week Moths caught per night Spray interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every 6 days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every 3 days

Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.

European Corn Borer Thresholds
Whorl stage: 30% or more of plants scouted show injury.
Pre-tassel-silk: 15% or more of plants scouted show injury.
Silk: 5 or more moths caught in pheromone traps in one week.

IPM Web Pages:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

The University of Maine is an equal opportunity/affirmative action institution.

Image Description: Sweet Corn

Image Description: Corn Earworm Feeding on Corn

Image Description: Fall Armyworm Injury on Corn Leaves

Image Description: Aphids on corn

Sweet Corn IPM Newsletter No. 8 – August 15, 2014

Sweet Corn IPM Newsletter No. 8 – August 15, 2014

Click on photos to enlarge.

PEST NUMBERS INCREASE IN MOST FIELDS

Fall Armyworm, European Corn Borer Moth Counts Rising

SITUATION
The recent storm has caused lodging in some fields, but corn plants can often come back up if the roots have not been badly damaged. However, spraying and harvesting lodged corn can be difficult. The stream of weather coming up from the south will likely cause pest numbers to increase in the near future, although for this week we have only seen relatively moderate increases in fall armyworm and European corn borer moth captures. The latter may indicate that a second generation is now getting underway.

European corn borer: Moth counts were generally higher in most locations this week, although a few sites still had no moths in the traps. This increase in trap captures suggests that a second generation of corn borer may be underway and could threaten silking corn in fields that are not on a spray schedule for corn earworm. Sabattus, Farmington, Livermore Falls, Nobleboro, Oxford and Palmyra were over the threshold of 5 moths per week in silking corn. The Farmington and Palmyra sites were also on spray regimes for corn earworm, so no additional sprays should be needed there. European corn borer feeding damage in pre-tassel corn was over the 15% threshold in Biddeford, Cape Elizabeth, Dayton, Poland Spring and Warren this week.

Corn earworm: Corn earworm moth counts are rising in some locations, as we expect late in the season when more weather comes up from the south carrying moths with it. A 6-day spray interval was recommended for corn earworm on silking fields in Biddeford, one Dayton site, Farmington, Palmyra, Warren, and one Wells site. A 5-day spray interval was recommended for one Cape Elizabeth site, Charleston, one Dayton site, New Gloucester, and North Berwick. A 4-day spray interval was recommended at one Lewiston site.

Fall armyworm: Moth counts continue to be erratic around the state, but were significantly higher in some sites this week (nearly 100 moths in a Cape Elizabeth trap). Fields in Biddeford, Cape Elizabeth, Monmouth, Nobleboro, Wales, Warren and one Wells site exceeded the threshold of 3 moths per week in silking corn. However, only the Monmouth, Nobleboro and Wales sites were not on a spray regime for corn earworm. Fall armyworm feeding damage on plants was only noted in Cape Elizabeth this week, where it exceeded the 15% damage threshold.

Squash vine borer moths were caught in pheromone traps in Biddeford and Cape Elizabeth this week, but did not exceed the threshold of five moths per week. You can download a free copy of the University of New Hampshire’s new fact sheet, Managing Squash Vine Borer Problems in New Hampshire from their website.

Picnic beetles can become a problem during the late summer on silking corn. These beetles are about 1/4 inch long, black with orange spots. They can often be found on stalks and ears that are infested with European corn borer or fall armyworm, feeding on sap at an entry or exit hole. They are also known to feed on the silks. While this does little damage, customers may object to finding the insects in their bags. Sprays to control corn earworm should provide control of these beetles if they are found in your field.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management Office
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259          Orono, ME 04473
207.933.2100                           1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Moths
ECB
Moths
FAW
Moths
%Feeding
Damage
Recommendations / Comments
Biddeford 2 0 5 22% 6-day spray interval recommended on all silking corn
Cape Elizabeth I 1 0 2 13% No spray recommended
Cape Elizabeth II 6 2 97 50% 5-day spray interval recommended on all silking corn
Charleston 5 4 0 5-day spray interval recommended on all silking corn
Dayton I 3 0 0 6-day spray interval recommended on all silking corn
Dayton II 6 0 1 38% 5-day spray interval recommended on all silking corn
Farmington 2 10 1 6-day spray interval recommended on all silking corn
Levant 1 3 0 3% No spray recommended
Lewiston I 9 3 0 0% 4-day spray interval recommended on all silking corn
Lewiston II 0 0 0 3% No spray recommended
Livermore Falls 1 5 1 0% One spray recommended for ECB on silking corn
Monmouth 0 4 18 One spray recommended for FAW on silking corn
New Gloucester 6 1 0 8% 5-day spray interval recommended on all silking corn
Nobleboro 1 35 8 One spray recommended for ECB+FAW on silking corn
No. Berwick 7 0 0 7% 5-day spray interval recommended on all silking corn
Oxford 1 7 2 2% One spray recommended for ECB on silking corn
Palmyra 2 6 0 6-day spray interval recommended on all silking corn
Sabattus 0 81 0 One spray recommended for ECB on silking corn
Wales 1 0 6 6% One spray recommended for FAW on silking corn
Warren 2 3 27 35% 6-day spray interval recommended on all silking corn
Wells I 0 0 0 4% No spray recommended
Wells II 2 1 3 4% 6-day spray interval recommended on all silking corn

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm

Corn Earworm Spray Thresholds for Pheromone Traps

Moths caught per week Moths caught per night Spray interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every 6 days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every 3 days

Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.

European Corn Borer Thresholds
Whorl stage: 30% or more of plants scouted show injury.
Pre-tassel-silk: 15% or more of plants scouted show injury.
Silk: 5 or more moths caught in pheromone traps in one week.

IPM Web Pages:

http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

The University of Maine is an equal opportunity/affirmative action institution.

Image Description: Sweet Corn

Image Description: European Corn Borer Larvae on Pre-tassel Stage Corn

Image Description: Corn Earworm Larvae

Image Description: Two Squash Vine Borer Moths

Image Description: Sap beetle on strawberry

Sweet Corn IPM Newsletter No. 6 – July 31, 2014

Sweet Corn IPM Newsletter No. 6 – July 31, 2014

Click on photos to enlarge.

PEST PRESSURE MODERATE AS CORN HARVEST BEGINS

Corn Earworm and Fall Armyworm Counts Low, but Still Threaten Silking Corn

SITUATION
Corn harvest is getting into full swing in southern Maine. High winds associated with the numerous thunderstorms have caused minor lodging in some fields. Excessive rainfall may also result in poor herbicide performance and leaching of fertilizer, especially nitrogen. Pest numbers remain relatively moderate, although silking corn in most locations requires protection against corn earworm and/or fall armyworm.

European corn borer: Moth counts continue to decline this week, suggesting that the first generation of this insect may be coming to an end. Most sites had no moths in the traps. Only the Sabattus site was over the threshold of 5 moths per week in silking corn. European corn borer feeding damage was only over the 15% threshold in Wales.

Corn earworm: Corn earworm remains widely distributed but moth counts are still moderate. A 6-day spray interval was recommended for corn earworm on silking fields in Dayton, Garland, Gray, Monmouth, Wales, New Gloucester, Nobleboro, North Berwick, Oxford and Palmyra. A 5-day spray interval was recommended for Biddeford, one Cape Elizabeth site, Charleston, Levant, Lewiston, Sabattus, Warren and one Wells location.

Fall armyworm: Moth counts are variable around the state this week. Fields in Biddeford, Cape Elizabeth, Dayton, Garland, Levant, Lewiston, Monmouth and Warren exceeded the threshold of 3 moths per week in silking corn. However, only the Garland site and one Lewiston site were not on a spray regime for corn earworm. Feeding damage on plants was only noted in New Gloucester this week, but did not exceed the 15% damage threshold.

Squash vine borer moths were caught in pheromone traps in Biddeford, Dayton, New Gloucester and Wells this week. The threshold of five moths per week was exceeded at the Biddeford, Dayton and New Gloucester sites. Vine borers threaten summer squash, winter squash and pumpkins. See the New England Vegetable Management Guide for control options.

Corn Rust: Rust is a fungus disease that causes reddish-brown pustules to form on the leaves, stalks and husks, reducing the visual quality of the ears. Severe infections can reduce ear size, especially if they occur prior to tasseling. Typically, corn rust does not become a problem until late in the season, because it can’t overwinter in Maine and must move in from the south. A fungicide spray for rust would only be recommended if the infection were noticed in a field prior to tasseling. Later infections are unlikely to cause enough damage to the crop to justify control measures. Materials available to control corn rust include Bravo®, Quilt® and maneb/mancozeb.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management Office
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259         Orono, ME 04473
207.933.2100                          1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Moths
ECB
Moths
FAW
Moths
%Feeding
Damage
Recommendations / Comments
Biddeford 4 4 11 6% 5-day spray interval recommended on all silking corn
Bowdoinham 0 0 0 0% No spray recommended
Cape Elizabeth I 7 2 3 0% 5-day spray interval recommended on all silking corn
Cape Elizabeth II 0 1 43 One spray recommended for FAW on silking corn
Charleston 6 0 0 5-day spray interval recommended on all silking corn
Dayton 3 0 5 6-day spray interval recommended on all silking corn
Farmington 0 0 0 0% No spray recommended
Garland 2 0 5 2% 6-day spray interval recommended on all silking corn
Gray 3 0 0 13% 6-day spray interval recommended on all silking corn
Levant 4 0 5 3% 5-day spray interval recommended on all silking corn
Lewiston I 7 0 4 3% 5-day spray interval recommended on all silking corn
Lewiston II 0 0 4 One spray recommended for FAW on silking corn
Livermore Falls 0 0 0 1% No spray recommended
Monmouth 2 1 12 9% 6-day spray interval recommended on all silking corn
New Gloucester 2 0 0 3% 6-day spray interval recommended on all silking corn
Nobleboro 2 0 6-day spray interval recommended on all silking corn
No. Berwick 3 0 0 6-day spray interval recommended on all silking corn
Oxford 2 0 1 8% 6-day spray interval recommended on all silking corn
Palmyra 2 2 0 5% 6-day spray interval recommended on all silking corn
Sabattus  0  12  1  1% One spray recommended for ECB on silking corn
Wales  3  0  1  20%  6-day spray interval recommended on all silking corn
Warren 5 0 8 1% 5-day spray interval recommended on all silking corn
Wells I 1 0 0 0% No spray recommended
Wells II 5 0 2 5-day spray interval recommended on all silking corn

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm

Corn Earworm Spray Thresholds for Pheromone Traps

Moths caught per week Moths caught per night Spray interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every 6 days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every 3 days

Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.

European Corn Borer Thresholds
Whorl stage: 30% or more of plants scouted show injury.
Pre-tassel-silk: 15% or more of plants scouted show injury.
Silk: 5 or more moths caught in pheromone traps in one week.

IPM Web Pages:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

The University of Maine is an equal opportunity/affirmative action institution.

 

Image Description: Sweet Corn

Image Description: Wind Blown Corn Field

Image Description: Adult Fall Armyworm

Image Description: Squash Vine Borer Larva

Image Description: Rust on Corn

Sweet Corn IPM Newsletter No. 5 – July 28, 2014

Sweet Corn IPM Newsletter No. 5 – July 28, 2014

Click on photos to enlarge.

EARLY CORN HARVEST UNDERWAY

Pest Pressure Remains Moderate for Most Locations

SITUATION
Hot weather and adequate moisture have provided good growing conditions for corn. Early harvest is underway in southern Maine and many fields are now silking, meaning they are now more susceptible to all of the major corn pests. However, in spite of a recent spate of storm fronts from the west, pest numbers have remained relatively moderate in most locations.

European corn borer: With the exception of two northern sites, moth counts were very low this week. Most sites had no moths in the traps. However, silking fields in Levant and Palmyra were over the threshold of 5 moths per week in silking corn. The Levant site was also on a spray regime for corn earworm, so no additional spray was recommended. European corn borer feeding damage was over threshold in pre-tassel to tasseling fields only at our Biddeford site this week.

Corn earworm: While corn earworm was widely distributed throughout our sites this week, moth counts were moderate. However, many later planted fields are now coming into silk and will need to be protected. A 6-day spray interval was recommended for corn earworm on silking fields in North Berwick, Wells, Biddeford, Cape Elizabeth, Bowdoinham, Gray, Farmington, one Lewiston site and Charleston. A 5-day spray interval was recommended for one Dayton site and one Lewiston site, Sabattus, Warren, Nobleboro and Levant.

Fall armyworm: Moth counts were higher in a few locations this week. Fields in Cape Elizabeth, Garland, Lewiston, Monmouth and Nobleboro exceeded the threshold of 3 moths per week in silking corn. However, only the Garland site was not also on a spray regime for corn earworm. Feeding damage on plants was noted this week in fields in Biddeford, Cape Elizabeth and Sabattus. Although not yet over threshold on it’s own, when combined with European corn borer damage the total feeding exceeded the 15% threshold in Biddeford.

Squash vine borer moths were caught in pheromone traps in Biddeford, Oxford and Wells this week. The threshold of five moths per week was exceeded only at the Wells site. Vine borers threaten summer squash, winter squash and pumpkins. See the New England Vegetable Management Guide for control options.

Potato leafhopper alert: We are seeing signs of potato leafhopper in vegetable and strawberry fields this week. These small, bullet-shaped insects feed on plant sap from the undersides of leaves, causing the leaves to become curled, stunted and yellow-streaked. Beans are often the first crop to show symptoms, but other crops are also susceptible, including potatoes and strawberries. To scout for leafhoppers, brush the leaves of the plants with your hand. The small, whitish adults can be seen flying off the plant. Look for small, light green leafhopper nymphs on the underside of injured leaves. They are about 1/16 inch long. When touched, they will crawl sideways in a crab-like manner. Controls for potato leafhoppers are listed in the New England Vegetable Management Guide.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management Office
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259          Orono, ME 04473
207.933.2100                           1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Moths
ECB
Moths
FAW
Moths
%Feeding
Damage
Recommendations / Comments
Biddeford 2 0 2 17% 6-day spray interval recommended on all silking corn
Bowdoinham 3 0 1 4% 6-day spray interval recommended on all silking corn
Cape Elizabeth I 3 0 3 6% 6-day spray interval recommended on all silking corn
Cape Elizabeth II 3 0 12 2% 6-day spray interval recommended on all silking corn
Charleston 2 0 0 6-day spray interval recommended on all silking corn
Dayton I 0 0 0 No spray recommended
Dayton II 6 0 0 12% 5-day spray interval recommended on all silking corn
Farmington 2 0 2 1% 6-day spray interval recommended on all silking corn
Garland 1 0 5 0% One spray recommended for FAW on silking corn
Gray 3 0 0 6-day spray interval recommended on all silking corn
Levant 4 6 0 2% 5-day spray interval recommended on all silking corn
Lewiston I 5 0 10 5% 5-day spray interval recommended on all silking corn
Lewiston II 3 0 2 6-day spray interval recommended on all silking corn
Livermore Falls 0 0 0 0% No spray recommended
Monmouth 1 2 11 No spray recommended (no silking corn)
Nobleboro 5 0 3 1% 5-day spray interval recommended on all silking corn
No. Berwick 2 0 0 6-day spray interval recommended on all silking corn
Oxford 1 0 1 2% No spray recommended
Palmyra 1 19 1 3% One spray recommended for ECB on silking corn
Sabattus 5 2 0 13% 5-day spray interval recommended on all silking corn
Wales 1 0 2 0% No spray recommended
Warren 7 0 2 0% 5-day spray interval recommended on all silking corn
Wells I 3 0 0 3% 6-day spray interval recommended on all silking corn
Wells II 1 0 0 0% No spray recommended

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm

Corn Earworm Spray Thresholds for Pheromone Traps

Moths caught per week Moths caught per night Spray interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every 6 days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every 3 days

Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.

European Corn Borer Thresholds
Whorl stage: 30% or more of plants scouted show injury.
Pre-tassel-silk: 15% or more of plants scouted show injury.
Silk: 5 or more moths caught in pheromone traps in one week.

IPM Web Pages:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

The University of Maine is an equal opportunity/affirmative action institution.

Image Description: Sweet Corn

Image Description: Corn Earworm

Image Description: Fall Armyworm on Corn Silk

Image Description: Two Squash Vine Borer Moths

Image Description: Potato Leafhopper

Sweet Corn IPM Newsletter No. 4 – July 18, 2014

Sweet Corn IPM Newsletter No. 4 – July 18, 2014

Click on photos to enlarge.

CORN EARWORM COUNTS CLIMBING

Pest Pressure Now Moderate for Most Locations

SITUATION
Despite a series of storms coming up from the south, corn pest pressure has remained moderate in most locations this week. Harvest of early corn planted under plastic will likely start next week in southern Maine.

European corn borer:  Moth counts were erratic again this week, with some locations having the highest numbers of the season, while others had none. Silking fields in Dayton, Lewiston, Livermore Falls, Nobleboro and Sabattus were over the threshold of 5 moths per week in silking corn. The Lewiston, Nobleboro and Sabattus sites were also on a spray regime for corn earworm, so no additional spray was recommended. European corn borer feeding damage was over threshold in pre-tassel to tasseling fields in Biddeford, Nobleboro, North Berwick and Sabattus this week.

Corn earworm:  Most locations have now caught at least one corn earworm moth, and counts have risen in a few locations this week. But moth numbers are still relatively low in many fields, given the recent storms moving in from the south. A 6-day spray interval was recommended for corn earworm on silking fields in one Cape Elizabeth location, one Dayton location, Gray, New Gloucester, Nobleboro, North Berwick, Sabattus and one Wells location. A 5-day spray interval was recommended for one Cape Elizabeth site and one Lewiston site. A 4-day spray interval for silking corn was recommended for Wales and Warren.

Fall armyworm:  Moth counts were mostly very low this week. Only one site in Cape Elizabeth exceeded the threshold of 3 moths per week in silking corn. However, this field was also on a spray regime for corn earworm, so no additional sprays should be needed. Feeding damage on plants was noted this week in fields in Biddeford, North Berwick and one Wells site. Although not yet over threshold on it’s own, when combined with European corn borer damage the total feeding exceeded the 15% threshold.

Japanese Beetles are becoming plentiful in southern and mid-state areas. These insects often find their way into cornfields and may feed on the silks of developing ears, causing poor tip fill. Sprays for corn earworm (except Bt’s) will often control the Japanese beetle as well.

Squash vine borer moths were caught in pheromone traps in Biddeford, Cape Elizabeth, Dayton, New Gloucester and Wells this week. This week’s counts were some of the highest we’ve seen. The threshold of five moths per week was exceeded in Dayton, New Gloucester and Biddeford.  Vine borers threaten summer squash, winter squash and pumpkins. See the New England Vegetable Management Guide for control options.

Late Blight Update:  Infections have been confirmed from potatoes in commercial fields and home gardens in southern Maine. With hot, humid weather, this disease can spread rapidly through a region. Growers should scout their potato and tomato fields for symptoms and apply preventative fungicides. For more information visit our Cooperative Extension Publications website and the 2014-2015 New England Vegetable Management Guide.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management Office
P.O. Box 179                              491 College Avenue
Monmouth, ME  04259         Orono, ME  04473
207.933.2100                           1.800.287.0279

 

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Moths
ECB
Moths
FAW
Moths
%Feeding
Damage
Recommendations / Comments
Biddeford 0 1 1 18% One spray recommended for ECB + FAW feeding
Cape Elizabeth I 2 3 0 5% 6-day spray interval recommended on all silking corn
Cape Elizabeth II 4 0 10 5-day spray interval recommended on all silking corn
Charleston 0 0 1 No spray recommended
Dayton I 0 7 0 One spray recommended for ECB on silking corn
Dayton II 2 0 1 11% 6-day spray interval recommended on all silking corn
Farmington 1 2 1 2% No spray recommended
Garland 1 0 0 0% No spray recommended
Gray 2 1 0 6-day spray interval recommended on all silking corn
Levant 0 2 0 0% No spray recommended
Lewiston I 6 5 0 5-day spray interval recommended on all silking corn
Lewiston II 1 3 0 0% No spray recommended
Livermore Falls 1 12 0 2% One spray recommended for ECB on silking corn
Monmouth 1 0 0 No spray recommended
New Gloucester 2 0 1 1% 6-day spray interval recommended on all silking corn
Nobleboro 3 5 0 29% 6-day spray interval recommended on all silking corn
No. Berwick 2 0 0 41% 6-day spray interval recommended on all silking corn
Oxford 0 4 0 1% No spray recommended
Palmyra 0 2 0 0% No spray recommended
Sabattus 3 8 0 23% 6-day spray interval recommended on all silking corn
Wales 8 1 0 0% 4-day spray interval recommended on all silking corn
Warren 9 0 1 4-day spray interval recommended on all silking corn
Wells I 0 2 0 8% No spray recommended
Wells II 2 2 1 2% 6-day spray interval recommended on all silking corn

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm

Corn Earworm Spray Thresholds for Pheromone Traps

Moths caught per week Moths caught per night Spray interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every 6 days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every 3 days

Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.

European Corn Borer Thresholds
Whorl stage: 30% or more of plants scouted show injury.
Pre-tassel-silk: 15% or more of plants scouted show injury.
Silk: 5 or more moths caught in pheromone traps in one week

IPM Web Pages:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the State of Maine and the U.S. Department of Agriculture cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

Image Description: Sweet Corn

Image Description: European Corn Borer Damage on Pre-tassel Stage corn

Image Description: Corn Earworm Moth

Image Description: Fall Armyworm Eggs on Corn

Image Description: Japanese Beetle

Image Description: Two Squash Vine Borer Moths

Image Description: Late Blight on Potato Leaf

Strawberry IPM Newsletter No. 6 – July 16, 2014

Strawberry IPM Newsletter No. 6 – July 16, 2014

Click on photos to enlarge.

RENOVATION AND WEED MANAGEMENT ISSUE

Time to Get Your Strawberry Beds Ready for Next Year

Be Ready to Manage Pests in Day-Neutral Strawberries

A cold, nearly snowless period in late December to early January resulted in some moderate winter injury to many strawberry fields around the state this spring.  But favorable spring growing conditions with little to no frost issues resulted in a pretty good crop in most fields. Weather conditions for the harvest seemed often too hot or rainy, especially during the all-important weekends, but customer demand was strong throughout the relatively short season. Pest pressure in most fields was pretty light throughout the season. Insects, including tarnished plant bug and strawberry bud weevil or clipper appeared fairly late and often in low numbers. While spider mites were hardly an issue, cyclamen mites were present in many fields, causing yellowing and dwarfing of affected plants. Root weevils and white grubs were an issue in some fields, especially where problems had been observed last year. Applications of both soil insecticides and parasitic nematodes appear to have helped reduce the problem in most situations. Disease pressure was also light in most fields. Timely fungicide sprays kept gray mold to a minimum, and foliar diseases, such as powdery mildew and leaf spot only began to show up towards the end of the season.

Don’t forget about your strawberries after harvest. Follow the recommended renovation steps listed below for matted row strawberries as soon after harvest as possible; and continue to scout for and manage disease, insect and weed problems as they arise. Some of the more common issues to be alert for during the summer are listed below.

DISEASES:  Foliar diseases should be monitored in your fields by regularly examining leaves. All of the common leaf diseases were present in fields this spring and we should expect that they will continue to be a problem through the summer. The most common summer diseases are powdery mildew, leaf spot and leaf scorch. Fungicides available for these diseases include captan, Topsin-M®, Cabrio®, and Pristine®. See the New England Small Fruit Management Guide for detailed descriptions of these diseases and their management.

Black root rot is a disease complex which can be brought on by a combination of problems, including nematodes, soil fungi (Rhizoctonia, Pythium), herbicide carryover, and soil compaction. Plants become weak and may wilt and die. Roots on affected plants are black and poorly developed. This tends to be a problem in fields that have been in strawberries constantly for many seasons, and in fields that are under stress in other ways, such as winter injury. Rotating fields to crops other than strawberries for at least three years is an important management strategy for black root rot. Improving soil drainage and breaking up hardpans in the soil may also help. Pre-plant root dips with azoxystrobin (Abound®) may also reduce incidence of black root rot in some fields.

INSECTS:  If black vine weevils or strawberry root weevils are a problem in a strawberry field that you would like to carry over, bifenthrin (Brigade®, Bifenture®) can be applied when adult feeding is noticed (usually until mid-late July). Look for notching along the leaf edges and the presence of the black or brown snout beetles. Applications should be made at night when these insects are active, and the highest rate of the insecticide should be used. For control of the grubs a soil drench of Platinum® (thiamethoxam) insecticide should be applied during the fall and/or early spring when the grubs are active in the soil. This product has a 50 day pre-harvest interval and may also be used as a pre-plant or planting treatment for root weevils. Parasitic nematodes such as Heterorhabditis bacteriophora or Steinernema feltiae can also be applied to provide control of root weevil grubs in late August. Nematodes require specialized handling and application. Contact us or talk with one of the suppliers for more details. See the New England Small Fruit Management Guide for sources.

White grubs have been an increasing problem in recent years.  The grubs may be the larvae of several species of scarab beetles, including June beetles, rose chafers, Japanese beetles, Asiatic garden beetles and European chafers. The beetles lay their eggs in June and July and the grubs feed on the roots of strawberries from July through mid September. Affected plants will be stunted and wilted and may die during dry periods. Pulling up plants reveals that roots have been chewed off about an inch below the soil line. Sifting through the soil below the plants may reveal the whitish crescent-shaped grubs which can range in size from 3/8 inch to almost 1 ½ inches long, with six legs near the head and a swollen rear-end. The two most effective periods to treat plantings for grubs are in the spring prior to when they pupate (May) and in the late summer when the next generation is actively feeding (late August). Materials should be applied with plenty of water to moist soil to be sure they reach the root zone. Materials currently registered for control of grubs include Platinum® and Admire Pro®. Parasitic nematodes can also provide control of grubs and should be applied with similar timing. Nematodes are very sensitive to ultraviolet light and dehydration and must be applied with lots of water. See the New England Small Fruit Management Guide for sources of parasitic nematodes.

Strawberry rootworm (not root weevil) is a small (1/8″) dark brown to black beetle which feeds on strawberry foliage, causing it to look skeletonized. The small larvae feed on strawberry roots, further weakening the plant. Adult feeding damage on the leaves usually occurs in late July through August. Heavy rootworm feeding weakens strawberry plants so control is warranted when injury is noticed.

Keep a lookout for potato leafhoppers, which can weaken strawberry plants and spread disease. The potato leafhopper does not overwinter in Maine, but must fly in from southern states. These small, bullet-shaped insects feed on plant sap from the undersides of leaves, causing the leaves to become curled, stunted and yellow-streaked. Symptoms are often first noticed in new strawberry plantings, but leafhoppers will also infest older plantings and a variety of vegetables, flowers and fruit crops. To scout for leafhoppers, brush the leaves of the plants with your hand. The small, whitish adults can be seen flying off the plant. Examine the underside of some injured leaves. Look for small, light green leafhopper nymphs. They are about 1/16 inch long. When touched, they will crawl sideways in a crab-like manner. Controls for potato leafhoppers include malathion, carbaryl or Provado®.

MITESTwo-spotted spider mites can increase significantly during the summer. Continue to take leaf samples for spider mites throughout the summer. If more than 25% of a 60-leaf sample has mites, controls should be applied. Summer is an ideal time to use predatory mites to control pest mites, because they prefer warm temperatures, and there is less chance of an insecticide spray that might kill them. Amblyseius fallacis can provide good control of two-spotted spider mites when they are released at a rate of about 10,000 mites per acre. Predator mite releases should only be made after a spider mite infestation has been found in the field. Releasing predators into a clean field will often result in them dying, due to a lack of food. See the New England Small Fruit Management Guide for sources of predatory mites.

Cyclamen mites:  Many fields were infested with these mites this spring, and summer may provide a good opportunity to control them. Plants showing weak growth and yellow, crinkled leaves may be infested with cyclamen mite. These mites are very small and reside down in the crown of the strawberry plant feeding on the developing leaves. They are very hard to see, even with magnification. Miticides such as Thionex®, Kelthane® or Portal® can be effective, but must be applied with lots of water to be sure that the material is carried down into the crowns.

WEEDS:  Weeds can become a big problem during the summer because they are often forgotten among all the other demands on our time and because of limited control options. However, the importance of good weed management should not be underestimated.  Keeping weeds under control this summer will prevent future infestations. Here’s a summary of weed control options for strawberries:

1.  Cultivation:  Following renovation, cultivation between strawberry rows can provide effective temporary control of annual weeds. Several types of cultivators are available which will work well in strawberry beds. Cultivators can also be used to help sweep runners into the plant rows.

2.  DCPA (Dacthal®):  A pre-emergent herbicide used in the early spring, late fall or after renovation. It offers good, short-term control of some annual broadleaf weeds and grasses. It is weak on ragweed, galinsoga, smartweed, shepherd’s purse and mustard. Its action will be improved if worked into the soil by irrigation or light cultivation, and it tends to work best in lighter, warmer soils. This may be used as an alternative to terbacil or napropamide when there is a high risk of plant injury from those products.

3.  Napropamide (Devrinol®):  A pre-emergent herbicide which provides good control of annual grasses, volunteer grains and some broadleaf weeds. It is typically applied just before mulching in the fall. Split applications have become popular due to the loss of other pre-emergent herbicides, e.g. half maximum rate application after renovation or in late summer after desired daughter plants have rooted, and a second half rate application once the strawberry plants are dormant. Napropamide should be activated by irrigation, rainfall or light cultivation within 24 hours of application. Repeated long-term use of this material, i.e. with no crop rotation, may eventually result in poor daughter plant establishment, due to rooting inhibition.

4.  Terbacil (Sinbar®):  An effective pre-emergent herbicide with some post-emergent activity, which should be applied at renovation time – after mowing and tilling the beds, but before new growth begins. A second application can be made in late fall, after the plants are dormant. No more than 6 oz. may be applied in a single application, and no more than 8 oz. may be applied in one season. An example of one season’s use could be 5 oz. applied at renovation and 3 oz. applied in the late fall, the latter in addition to napropamide or DCPA. Terbacil can cause injury to strawberry plants. It is important to determine appropriate rates for each location.

5.  Sethoxydim (Poast®): A post-emergent herbicide for control of actively growing grasses. It will not control broadleaf weeds. It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days. Do not use sethoxydim within 6 weeks of terbacil (Sinbar®) applications, to avoid leaf injury.  Sethoxydim should be used in combination with a crop oil concentrate. Do not tank mix with 2, 4-D.

6.  Clethodim (Arrow®, Prism®, Select®):  A post-emergent herbicide, similar in activity to Poastâ, for control of actively growing grasses. It will not control broadleaf weeds. It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days. Clethodim should be used in combination with a crop oil concentrate.

7.  Paraquat (Gramoxone Inteon®):  A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds. Paraquat will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries. It should be used in combination with a nonionic surfactant. Paraquat should not be applied within 21 days of harvest or more than three times in one season.

8.  Pelargonic Acid (Scythe®):  A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds. Scythe® will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries. This product has a relatively low toxicity and no residual soil activity. It has a strong, unpleasant odor.

9.  2,4-D Amine (Formula 40®, Amine 4):  A post-emergent herbicide effective on most broadleaf perennial weeds. It will not control grasses, nor offer any pre-emergent control. 2,4-D should be applied immediately after harvest is complete if emerged broadleaf weeds are a problem. After application, the bed should be left undisturbed for three to five days, before mowing the leaves off the plants. This allows time for the material to be taken in by the weeds. This material can also be used when the plants are dormant (late fall or early spring) to control winter annuals and biennials. Fall applications may result in injury to the strawberries if the plants are not completely dormant. Do not tank mix 2,4-D with sethoxydim (Poast®).

10.  Flumloxazin (Chateau®):  A pre-emergent herbicide for control of broadleaf weeds, including dandelion and shepherd’s purse. For use in the fall when plants are dormant for control of weeds the following spring.

11.  Pendimethalin (Prowl H20®):  A pre-emergent herbicide that may be applied as a band with a shielded sprayer between the rows of strawberries. No weed control will be provided within the plant rows, and contact of this product on the strawberry plants will cause injury. May not be applied within 35 days of harvest.

The use of herbicides alone rarely gives complete weed control. Some hand weeding will be necessary. To provide good weed control throughout the life of a strawberry bed, growers should concentrate on crop rotation and good pre-plant weed control.

 

Strawberry Bed Renovation Review

Bed renovation should begin as soon after harvest as possible. The earlier the beds get renovated, the more time runner plants have to develop, which means larger crowns and more flower buds for next year. Early renovation also improves weed management by tilling in many weeds before they go to seed, and can help with insect and foliar disease control by interfering with life cycles at a critical stage of development. The first step in the bed renovation process is to determine which beds should be carried over for another year and which should be plowed down and put into a crop rotation. Beds that did not suffer much from winter injury, had good production and a good plant stand with no major weed, insect or disease problems should be carried over for another year. Beds that do not meet these criteria should be plowed down and seeded to a suitable cover crop to reduce weed, insect and disease problems that have developed, and to increase soil organic matter content. Ideally, beds that are plowed down should be rotated out of strawberries for at least three years. If properly managed, crop rotation will greatly reduce pest problems and improve the vigor and longevity of strawberry beds without the need for soil fumigation.

Renovating a strawberry bed is basically a thinning process to promote healthy new growth that can support a good crop next spring. While some parts of the following renovation scheme may be modified for individual situations, all beds should undergo the following steps once harvest is complete.

1.  Broadleaf weed control:  If perennial broadleaf weeds such as dandelion, shepherd’s purse, daisy or goldenrod are a problem and/or a high population of annual broadleaf weeds such as lambsquarters, sorrel or pigweed are present, hand-pull as many as possible, especially within the plant rows, and/or apply 2,4-D amine (Formula 40®).

2.  Leaf mowing:  Four to five days following the 2,4-D application (or immediately if 2,4-D was not applied) mow off the leaves of the strawberries about 1 ½ inches above the crowns. If the planting is weak, it is recommended that this step of the renovation process be skipped.

3.  Fertilization:  Apply 40 to 60 pounds of actual nitrogen per acre (use the higher rate on sandy soils and fields where growth has been weak). Phosphorus and potassium applications should be made according to soil test recommendations. Soil testing kits and information are available from your county Cooperative Extension office.

4.  Plant thinning:  For the single matted row system, strawberry plant rows should not be any wider than 24 inches. After mowing off the leaves, till the sides of the rows to narrow the beds back to a width of 12 to 18 inches. Use the wider setting for varieties that tend to throw few runners or any fields experiencing drought stress.  Set the tiller so that it incorporates the mowed leaves and spreads about one inch of soil over the remaining crowns at the same time. This will reduce leaf disease and mite problems, and help stimulate new root growth on the remaining plants.

5.  Pre-emergent weed control:  To control annual weeds, apply terbacil (Sinbar® 80WP) according to label directions (2 to 6 oz. per acre). Be sure to follow all label precautions. To avoid plant injury, do not use terbacil if you do not intend to mow off the leaves. Napropamide (Devrinol®) or DCPA (Dacthal®) may be used as an alternative to terbacil at this time, as described below. If you are not using herbicides, regular cultivation, before weeds are more than 2” tall, will be needed throughout the summer.

6.  Subsoiling:  Soil compaction caused by tractor and picker traffic in the field can cause soil drainage problems and interfere with good root development. Using a subsoiling blade between the rows will break up compacted layers of soil and improve water infiltration. Subsoiling is best done late in the renovation sequence to prevent interference from straw and crop residues.

7.  Irrigation:  To encourage rapid plant growth and get the most out of fertilizers and herbicides, irrigate the beds regularly. Strawberries will grow best if they receive 1 ½ inches of water per week during the growing season.

Don’t forget your plants once these renovation steps are completed. Check the strawberry fields regularly during the summer for pest problems. Finding and managing problems early can prevent major problems next spring. Pay close attention to the following items:

NUTRITION:  Following the application of 40 to 60 pounds of actual nitrogen at renovation, another 20 pounds of nitrogen should be applied in mid- to late-August to stimulate flower bud development. One way to determine the nutrient status of strawberry plants during the summer is to have a leaf tissue analysis done. Tissue analysis offers a view of what is happening within the plant, and can spot any nutrient deficiencies. In combination with regular soil tests, tissue analysis will provide a complete picture of a field’s fertilizer needs. For more information about tissue analysis contact the UMaine Analytical Lab, 5722 Deering Hall, Rm. 407, University of Maine, Orono, ME 04469-5722, telephone: 207.581.2945.

 

Pest Management for Day-Neutral Strawberries

Most of the important pests that damage June-bearing varieties can be as much or more of a problem on day-neutral types. Because day-neutral strawberries will have buds, flowers and fruit all occurring at the same time, it is critical to pay close attention to the required number of days to harvest after a pesticide application, to be sure you can safely harvest ripe fruit while still protecting buds and blossoms. Some of the more important pests are listed below, along with currently recommended pesticides and days to harvest as stated on current labels.

Spotted wing drosophila (Drosophila suzukii) is a new pest, which is likely to be a concern for day- neutral strawberries, fall raspberries and blueberries. This is a small fruit fly, similar to those that hover around the bananas in your kitchen. However, this species will lay its eggs on fruit before it ripens, resulting in fruit that is contaminated with small white maggots just as it is ready to pick. Infested fruit quickly rots and has no shelf life. This insect can complete a generation in under two weeks, with each adult female laying hundreds of eggs. Therefore, millions of flies can be present soon after the introduction of just a few into a field. Frequently repeated insecticide sprays (1 to 2 per week) may be needed to prevent infestations once the insect is present in a field. Spotted winged drosophila can successfully overwinter here, although it may not build up to damaging levels until late in the summer. We have set out monitoring traps for spotted winged drosophila in fruit plantings around the state to determine the activity of this pest in Maine. However, these traps may not provide adequate early warning, i.e. when we find them in a trap they are probably already established in the field. We have found just a few spotted wing drosophila in Maine over the past two weeks, but not yet in damaging numbers. Products that provide good control of drosophila on strawberries include Radiant®, Brigade®, Danitol®, malathion and Assail®. Keeping fields clean of over-ripe and rotten fruit will also help reduce the incidence of this insect. For more information on identifying spotted wing drosophila and updates on populations around the state, visit our SWD blog.  Other spotted wing drosophila resources can be found on the websites of Michigan State University, Penn State, and University of New Hampshire.

Tarnished plant bug:  This is one of the most prevalent and persistent pests of day-neutral strawberries, because summer flowering coincides with peak populations of this insect. Adult and nymph stages feed on the flowers and developing fruit, causing them to have seedy ends and other malformations. Regular insecticide applications are often required to keep the damage in check. Scout the flower clusters for adults and nymphs often to determine if controls are necessary. Insecticide products for tarnished plant bug include:

Tarnished Plant Bug
Product Days to Harvest
Brigade® 0
Pyganic® 0
Assail® 1
Dibrom® 1
Rimon® 1
malathion 3


Two-spotted spider mites:  
Mites can become a problem during the summer when the growing conditions are warm and dry. In addition to infesting the leaves, mites can move onto the fruit, reducing marketability. Plants that are drought-stressed, over fertilized with nitrogen, or prone to dust covering, e.g. growing beside a dirt road, are especially prone to mite infestation. Predatory mites can be an effective means to control spider mites and keep them in check over the season. Releases should only be made when spider mites are present in the field to provide the predators with a source of food. Most of the products labeled for controlling spider mites will also kill predatory mites; so do not use these products after predators have been released. Scout for mites often during the season by examining the undersides of the leaves. Control is warranted if more the 25% of leaves examined have mites.

Two-Spotted Spider Mites
Product Days to Harvest
Brigade® 0
Zeal® 1
Vendex® 1
Acramite® 1
Danitol® 2
Agri-Mek® 2
Oberon® 3
Savey® 3
Kelthane® 3

Potato leafhoppers, sap beetles, thrips and spittlebugs may also become problems on day-neutral strawberries, but are less frequently observed than tarnished plant bug and spider mites. Recommendations for these insects can be found in the current edition of the New England Small Fruit Management Guide.

Foliar and fruit diseases also need to be managed on day-neutral strawberries, and should be controlled in much the same way as they are for June-bearing varieties. Most of the fungicide products labeled to control gray mold, powdery mildew, leaf spot and leaf scorch have either zero or one day to harvest, so protecting blossoms at the same time as fruit is near harvest should not be a problem; but be sure to check labels carefully and schedule your sprays and harvests accordingly. Anthracnose fruit rot can be especially troublesome for day-neutral strawberries, because it grows well under warm conditions and spreads by splashing water, which is encouraged on plastic mulch. Fungicides registered for control of anthracnose include Cabrio®, Abound®, Pristine® and Switch®, all of which have zero days to harvest restriction.

Important Reminder for Pesticide Users:  Fruit, vegetable or grain growers who use general use (over-the-counter) pesticides and annually sell more than $1,000 of plants or plant products intended for human consumption will be required to have an Agricultural Basic Pesticide Applicator License by April 15, 2015. In the past, only farmers using restricted use pesticides were required to have a pesticide applicators license. The new law extends the licensing requirement to all commercial growers who use pesticides. Training and testing sessions for unlicensed farmers will be held across the state this fall and winter. For more information contact the Pest Management Office at 1.800.287.0279.

Visit the 2014-2015 New England Small Fruit Management Guide online for more detailed pest information.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Avenue
Monmouth, ME  04259         Orono, ME  04473
207.933.2100                           1.800.287.0279

Where brand names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against products with similar ingredients.  Always consult product label for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

A Member of the University of Maine System

 

Image Description: Strawberries

Image Description: Powdery Mildew

Image Description: Leaf Spot

Image Description: Black Vine Weevil

Image Description: Strawberry Root Weevil Grub

Image Description: Strawberry Rootworm Beetle

Image Description: Potato Leafhopper

Image Description: Two-spotted Spider Mites

Image Description: Cyclamen Mite Damage

Image Description: Mowing Strawberry Leaves

Image Description: Strawberry Irrigation

Image Description: Sidedressed Strawberry Planting

Image Description: Male and Female Spotted Wing Drosophila Flies

Image Description: Large Tarnished Plant Bug Nymph

Image Description: Two-spotted Spider Mites

Image Description: Gray Mold on Strawberries

Sweet Corn IPM Newsletter No. 3 – July 10, 2014

Sweet Corn IPM Newsletter No. 3 – July 10, 2014

Click on photos to enlarge.

FALL ARMYWORM, CORN EARWORM THREATEN SILKING CORN

Late Blight Alert for Potatoes and Tomatoes!

SITUATION
Last weekend’s storm will likely increase insect activity by bringing up moths from the south. Fortunately, the winds were not strong enough to cause widespread lodging in cornfields. More fields are coming into silk as the warm temperatures continue to push growth.  More silking fields are now on a spray regime for corn earworm and/or fall armyworm. The first indication of late blight in Maine was found this week in a potato field in Buxton.

European corn borer:  Moth catches were higher in some locations this week but continue to be erratic. Silking fields in Cape Elizabeth and Sabattus were over the threshold of 5 moths per week in traps, and a spray for silking corn was recommended. European corn borer feeding damage was over threshold in pre-tassel to tasseling fields in Biddeford, Bowdoinham, Lewiston and Sabattus this week. Remember that sprays applied at pre-tassel tend to be more effective than whorl or tassel stage sprays, because the larvae are usually more exposed.

Corn earworm:  The impact of the tropical storm does not yet seem to be showing up in moth counts. Moths were higher in one Cape Elizabeth location and more sights are now catching their first moths, including our more northern sites, but there has not yet been a large bump in trap captures. A 6-day spray interval was recommended for early silking fields in Dayton, New Gloucester and one Lewiston site. A 4-day spray interval was recommended for one silking field in Cape Elizabeth.

Fall armyworm:  Moth counts were up significantly in some locations while others still have yet to catch their first fall armyworm.  Fields in Cape Elizabeth, New Gloucester and Lewiston were over the threshold of 3 moths per week in silking corn. However, these fields were also on a spray regime for corn earworm, so no additional sprays should be needed. The first feeding damage on plants from fall armyworm was noted this week in fields in Biddeford and Lewiston. Although not yet threatening alone, when combined with European corn borer damage the total feeding exceeded the 15% threshold.

Squash vine borer moths were caught in pheromone traps in North Berwick, Biddeford, Dayton and New Gloucester this week. The threshold of five moths per week was exceeded in North Berwick, Wells, Dayton and Biddeford. This pest threatens summer squash, winter squash and pumpkins. Unlike many moths, squash vine borer moths fly during the day. They are black and orange and resemble wasps. The moths lay eggs at the base of squash plants. The larvae bore into the base of the plants, causing vines to wilt and eventually collapse. See the 2014-2015 New England Vegetable Management Guide for control options.

Late Blight Alert! The first symptoms of late blight were found in a potato field in Buxton this week. This devastating disease of tomatoes and potatoes spreads via spores under warm, wet conditions. Growers should take precautions by applying preventative fungicides. See our publications website and the 2014-2015 New England Vegetable Management Guide for management options.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management Office
P.O. Box 179                             491 College Avenue
Monmouth, ME  04259         Orono, ME  04473
207.933.2100                           1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Moths
ECB
Moths
FAW
Moths
%FeedingDamage Recommendations / Comments
Biddeford 1 3 2 40% One spray recommended for ECB + FAW
Bowdoinham 0 3 0 22% One spray recommended for ECB
Cape Elizabeth I 0 5 0 5% One spray recommended for ECB on silking corn
Cape Elizabeth II 8 3 12 1% 4-day spray interval recommended on all silking corn
Charleston 0 0 0 0% No spray recommended
Dayton I 2 0 0 6-day spray interval recommended on all silking corn
Dayton II 2 0 0 9% 6-day spray interval recommended on all silking corn
Farmington 1 1 1 12% No spray recommended
Garland 1 6 1 0% No spray recommended (no silking corn)
Levant 0 4 1 0% No spray recommended (no silking corn)
Lewiston I 1 1 0 0% No spray recommended
Lewiston II 2 0 3 20% 6-day spray interval recommended on all silking corn
Livermore Falls 1 0 0 3% No spray recommended
New Gloucester 2 4 6 1% 6-day spray interval recommended on all silking corn
No. Berwick 0 0 1 10% No spray recommended
Oxford 0 1 0 5% No spray recommended
Palmyra 0 15 0 1% No spray recommended (no silking corn)
Sabattus 0 29 0 34% One spray recommended for ECB on silking corn
Wales 0 2 0 3% No spray recommended
Warren 0 0 0 13% No spray recommended
Wells I 1 0 0 5% No spray recommended
Wells II 0 0 1 0% No spray recommended

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm

Corn Earworm Spray Thresholds for Pheromone Traps

Moths caught per week Moths caught per night Spray interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every 6 days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every 3 days

Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.

European Corn Borer Thresholds
Whorl stage: 30% or more of plants scouted show injury.
Pre-tassel-silk: 15% or more of plants scouted show injury.
Silk: 5 or more moths caught in pheromone traps in one week.

IPM Web Pages:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the State of Maine and the U.S. Department of Agriculture cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

Image Description: Sweet Corn

Image Description: European Corn Borer Larvae on Pre-tassel Stage Corn

Image Description: Fall Armyworm Moths

Image Description: Two Squash Vine Borer Moths

Image Description: Late Blight on Potato Leaf

Sweet Corn IPM Newsletter No. 2 – July 3, 2014

Sweet Corn IPM Newsletter No. 2 – July 3, 2014

Click on photos to enlarge.

CORN BORER, CORN EARWORM AND FALL ARMYWORM MOTHS ACTIVE

Silking Corn Needs Protection in Early Fields

SITUATION
Cornfields are developing fast with the onset of warm (very warm) temperatures this week. Several early plantings are now in silk while others are coming into tassel. Any showers that arrive this weekend will be welcomed in early fields where conditions are very dry. All of the major corn pests have arrived and are active in cornfields in much of the state. These are especially a threat to early silking fields, which growers often spray lightly, if at all, assuming the major pests are not yet present in damaging numbers.

European corn borer:  Moth catches are spotty around the state this week with about half of the sites now catching moths. A field in Nobleboro was over threshold of 5 moths per week in an early field of silking corn. Another field in Warren was also over the threshold, but does not yet have corn in silk, so no spray was recommended. European corn borer feeding damage was over the 15% threshold in pre-tassel fields in Biddeford, Bowdoinham, New Gloucester, Sabattus, Livermore Falls and Nobleboro.

Corn earworm:  We are now finding corn earworm moths in most of our monitoring sites. Numbers are still low, and most fields do not yet have any silking corn that could be threatened by this pest. When more than one corn earworm moth is found at a site, all silking corn in the fields should be protected with a spray. Additional sprays are based on the average number of moths caught per week or per night (see table below). Only one field in Cape Elizabeth had moths over threshold and early silking corn. A 5-day spray interval was recommended at that location, based on a weekly moth catch of 4.

Fall armyworm:  Moths have arrived in many of the fields monitored this week, indicating that cornfields will soon start showing feeding damage from larvae. Fall armyworm caterpillars leave large ragged holes in the corn leaves and lots of sawdust-like waste within the whorl and developing tassels. We found two fields showing feeding damage this week. In silking fields, fall armyworm larvae may enter the ears through the silk channel, leaving little visible damage to the plant. For that reason, when more than 3 fall armyworm moths are caught in pheromone traps in a week a spray is recommended for all silking corn in a field. Only one field in Cape Elizabeth was over the threshold for silking corn this week. However, that same field was also on a spray schedule for corn earworm in silking corn, so no additional sprays should be required to control fall armyworm.

Japanese beetles should soon be appearing in southern and mid-state areas. These insects often find their way into cornfields and feed on the silks of developing ears, causing poor tip fill. Sprays for corn earworm (except Bt’s) will often control Japanese beetle as well.

Spotted wing drosophila:  The first capture of a spotted wing drosophila in Maine was reported this week from a wild blueberry field in Blue Hill. These small fruit flies can cause serious fruit losses in raspberries, blueberries and other soft fruits. The flies will only attack fruit that has begun to ripen, and we don’t expect populations to reach damaging levels for a few weeks. For more information visit our website: http://extension.umaine.edu/highmoor/news-events/.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management Office
P.O. Box 179                             491 College Avenue
Monmouth, ME  04259         Orono, ME  04473
207.933.2100                           1.800.287.0279

 

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Moths
ECB
Moths
FAW
Moths
%Feeding
Damage
Recommendations / Comments
Biddeford 0 4 2 25% One spray recommended for ECB on pre-tassel corn
Bowdoinham 2 0 0 28% One spray recommended for ECB on pre-tassel corn
Cape Elizabeth I 1 0 0 0% No spray recommended
Cape Elizabeth II 4 0 15 0% 5-day spray interval recommended on all silking corn
Dayton 0 0 0 0% No spray recommended
Dayton II 1 0 2 2% No spray recommended
Farmington 0 1 0 3% No spray recommended
Lewiston 4 2 1 1% No spray recommended (no silking corn)
Lewiston II 0 4 1 4% (no silking corn)
Livermore Falls 0 0 0 15% One spray recommended for ECB on pre-tassel corn
Monmouth 0 0 0 0% No spray recommended
New Gloucester 1 0 1 1% No spray recommended
Nobleboro 1 10 0 18% One spray recommended for ECB on pre-tassel-silk corn
No. Berwick 1 0 1 40% One spray recommended for ECB on pre-tassel corn
Oxford 1 1 0 4% No spray recommended
Sabattus 1 0 0 38% One spray recommended for ECB on pre-tassel corn
Wales 0 0 0 8% No spray recommended
Warren 0 24 0 0% No spray recommended (no silking corn)
Wells I 0 0 0 0% No spray recommended
Wells II 0 0 1 0% No spray recommended

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm

Corn Earworm Spray Thresholds for Pheromone Traps

Moths caught per week Moths caught per night Spray interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every 6 days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every 3 days

Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.

European Corn Borer Thresholds
Whorl stage: 30% or more of plants scouted show injury.
Pre-tassel-silk: 15% or more of plants scouted show injury.
Silk: 5 or more moths caught in pheromone traps in one week.

IPM Web Pages:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the State of Maine and the U.S. Department of Agriculture cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

Image Description: Sweet Corn

Image Description: European Corn Borer Moth

Image Description: Corn Earworm Moth

Image Description: Male Fall Armyworm Moth

Image Description: Male and Female Spotted Wing Drosophila Flies

Sweet Corn IPM Newsletter No. 1 – June 27, 2014

Sweet Corn IPM Newsletter No. 1 – June 27, 2014

Click on photos to enlarge.

2014 SWEET CORN PEST SEASON BEGINS!

European Corn Borer Moths Active, Larvae Feeding in Early Corn

The 2014 University of Maine Cooperative Extension Integrated Pest Management (IPM) program for sweet corn is underway. More than twenty volunteer farms are serving as pest monitoring and demonstration sites, with fields in North Berwick, Wells, Dayton, Cape Elizabeth, New Gloucester, Poland Spring, Auburn, Lewiston, Sabattus, Nobleboro, Warren, Monmouth, Wales, Wayne, Oxford, Farmington, Levant, Stillwater, Garland and East Corinth. Pheromone traps have been set up at these farms to monitor the adult (moth) stages of European corn borer, corn earworm and fall armyworm, and we have begun scouting the fields for feeding injury by insect larvae. The information collected at these sites along with management recommendations will be shared every week during the season through this newsletter and blog. If you would prefer to receive this newsletter via e-mail, give us a call at 207.933.2100 or send an e-mail message to: pamela.stpeter@maine.edu.

SITUATION
Farmers with well-drained fields were able to get some early plantings going in spite of a rather cool, wet start to the season. Early seedings started under clear plastic or fabric row covers are now in the pre-tassel to tassel stage, with one southern field already starting to show some silk. In spite of the wet conditions during the spring, some fields are starting to get a bit dry, so the recent rain was quite welcome. Warmer weather predicted for next week should speed up plant development. European corn borer moths have been active in some fields, as evidenced by some light feeding damage we have seen in some pre-tassel fields this week.

European corn borer:  We have set up pheromone traps for European corn borer this week, and we’ll start reporting on moth activity in the next issue. We found some feeding injury and very small larvae in pre-tassel fields this week, indicating that moths are now laying eggs on the undersides of corn leaves. The egg masses are small and look like overlapping fish scales. European corn borer overwinters in Maine, and is usually the first pest to become a significant problem. To monitor corn borer, we scout 100 corn plants in each field, examining twenty plants in a row at five different locations. This provides a good estimate of the total amount of injury in a field.

In the early stages, European corn borer feeding damage looks like small “pinholes” in the leaves. Whorl stage corn only needs to be sprayed if fresh feeding injury is found on 30% or more of the plants scouted in a field. Once the corn reaches the pre-tassel stage, the control threshold is lowered to 15% because larvae feeding on the later stages are more likely to move into the ears. On the tassels, feeding damage first appears as chewing and brown waste found in the small florets. After the tassel has emerged from the stalk, the larvae chew into the stalk just below it, often causing the tassel to fall over. Sprays during the pre-tassel stage, when both moths and larvae are present, reduce the opportunity for larvae to move into the stalks and ears of the plant. Once the larvae are in the stalks they are protected from sprays. Good spray coverage of the entire plant provides the most effective kill of larvae as they move from one part of the plant to another. Rotating the type of insecticide used also improves control. Materials registered for controlling European corn borer include Bacillus thuringiensis products (XenTari®, Dipel DF®), Avaunt®, Coragen®, Warrior®, Lannate®, Baythroid®, Asana®, Radiant®, Delta Gold®, Mustang®, Sevin XLR® and Larvin®. We found corn borer feeding injury in pre-tassel fields in Sabattus, Farmington, Livermore Falls, New Gloucester and Nobleboro this week; but only the field in Nobleboro exceeded the injury threshold. Once corn reaches the silk stage, sprays may be based on the number of corn borer moths caught in pheromone traps rather than feeding injury. European corn borer moths will lay eggs on flag leaves of silking corn, and the larvae can move into the ears without leaving visible feeding injury that would be noticed when scouting. If more than five moths are caught during a week in a field with silking corn, a spray is recommended. Varieties of corn genetically modified to produce the Bt toxin (e.g. Bt corn, Attribute® varieties), should not need to be sprayed to control European corn borer.

Corn earworm:  Pheromone traps are now set up around the state to monitor the arrival of corn earworm. Corn earworm generally appears in Maine in early July, but the actual date varies greatly. The arrival of this pest is only a concern for fields with corn in the silk stage. Fields not yet in silk do not need to be protected from corn earworm. When corn earworm moths start being caught at a site, all silking corn in the fields should be protected with a spray. These moths lay eggs on the fresh silks and the larvae move directly into the ears of corn. When corn earworm moths cannot find silking corn to deposit their eggs on, they may lay eggs on the leaves of younger corn. The larvae will feed on the foliage and tassels, similar to armyworm, until the ears become available. When larvae are found feeding on younger corn, the damage is accounted for, along with any borer or armyworm damage, to determine if a spray is warranted.

Fall armyworm:  This is usually the last serious corn insect pest to arrive in Maine. The moths must fly in from southern over-wintering sites, and tend to lay their eggs on the youngest corn available. When the larvae hatch, they chew large, ragged holes in the leaves, and may bore into developing ears. Larvae may also move into the ears through the silk channel, behaving similarly to corn earworm. Pheromone trap catches will indicate if there is a threat to silking corn. However, corn will usually be on a spray program for corn earworm when fall armyworm is present, and both insects would be controlled.

Do-It-Yourself IPM:  To get the most accurate information about the pest situation on your farm you should monitor the fields yourself on a regular basis. Pheromone traps and lures are available that can give you an accurate, early warning of the arrival of all of the major insect pests. Traps and lures can be purchased from pest management supply companies such as Gempler’s (1.800.382.8473) or Great Lakes IPM (517.268.5693).

To learn more about IPM scouting techniques, insect identification and control thresholds, order the fact sheet Managing Insect Pests of Sweet Corn available from the University of Maine Cooperative Extension. Color pictures are provided to help with insect identification, and a chart with spray thresholds is supplied to post near your sprayer for easy reference. You can download a copy from the UMaine IPM website or call the Pest Management Office at 1.800.287.0279.

IPM Web Pages:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management Office
P.O. Box 179                             491 College Avenue
Monmouth, ME  04259         Orono, ME  04473
207.933.2100                           1.800.287.0279

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the State of Maine and the U.S. Department of Agriculture cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

Image Description: Sweet Corn

Image Description: European Corn Borer Scouting

Image Description: European Corn Borer Moth

Image Description: European Corn Borer Damage on Pre-tassel Stage corn

Image Description: Corn Earworm Moth

Image Description: Fall Armyworm Moths

Image Description: Harstack Trap


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University of Maine Cooperative Extension


Contact Information

Cooperative Extension at Highmoor Farm
52 U.S. Route 202
Monmouth, Maine 04259-0179
Phone: 207.933.2100
The University of Maine
Orono, Maine 04469
207.581.1110
A Member of the University of Maine System