Posts Tagged ‘late blight’

Sweet Corn IPM Newsletter No. 6 – July 21, 2010

Wednesday, July 21st, 2010

Sweet Corn

For full page print version, please see link at the bottom.

Corn Earworm Has Arrived.  Protect Silking Corn!

Fall Armyworm a Threat to Younger Corn

SITUATION
Early corn harvest continues in Southern Maine.  Warm weather has kept later corn growing at a rapid pace, especially in irrigated fields.  Both corn earworm and fall armyworm have made stronger appearances this week, emphasizing the need to protect silking corn where these pests have been found.  Corn earworm populations are at their highest of the season and fall armyworm feeding injury is becoming more widespread.

Green Silk Stage

Green Silk Stage, photo by David Handley

European corn borer:  Moth counts are generally low again this week.  Only one spray was recommended for exceeding threshold for silking corn in Farmington.  Dresden was also over threshold, but already on a spray interval for corn earworm.   Larval feeding injury exceeded threshold in non-silking corn only when combined with fall armyworm feeding injury in one site in Wells this week.

European Corn Borer Larvae on Ear

European Corn Borer Larvae on Ear, photo by David Handley

Corn earworm:  Pheromone trap catches continue to be low in most locations this week.  Four-day spray intervals were recommended in Biddeford, one site in Cape Elizabeth, Charleston, one site in Dayton, Dresden, Levant, Nobleboro, North Berwick, and Old Town.  Five-day spray intervals were recommended in Jefferson, one Lewiston site, Monmouth, New Gloucester, Sabattus, and one Wells site.  Six-day spray intervals were recommended for silking corn fields in Corinth, one Dayton site, Livermore, Palmyra, and Warren.  Single moths were caught in Farmington, one Lewiston site, Oxford, Poland Spring, Readfield, and Wales; but these were not significant enough to warrant a spray.

Corn Earworm Larvae

Corn Earworm Larvae, photo by David Handley

Fall armyworm:  Moths exceeded threshold for silking corn in two locations this week, New Gloucester and Poland Spring.  The New Gloucester field was already on a spray interval for corn earworm, so no additional sprays should be needed.  A single spray to protect silking corn was recommended at the Poland Spring site.  Fall armyworm feeding injury exceeded the 15% threshold for pre-tassel stage corn in Biddeford, both sites in Cape Elizabeth, Dresden, North Berwick, Poland Spring, and combined with ECB at one site in Wells.  Single protective sprays were recommended on non-silking corn in all of these locations.

Fall Armyworm Injury on Corn Leaves

Fall Armyworm Injury on Corn Leaves, photo by David Handley

Late Blight:  Grower and Farm Stand Alert
Potato late blight, the disease that caused the significant crop losses for tomatoes and potatoes in Maine last year has just been confirmed at a sight in Waldoboro, and several other suspected sites are now being investigated.  An announcement is enclosed with more information.  Please feel free to contact the University of Maine Cooperative Extension Pest Management Office with any questions.

Late Blight Hotline:
For the most recent information, call the IPM Hotline at 207.760.9IPM (207.760.9476)PMO@umext.maine.edu

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

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

Location CEWMoths ECBMoths FAWMoths %ECB Damage Recommendations / Comments
Biddeford 18 0 2 38% 4-day spray interval recommended for all silking corn
Cape Elizabeth I 0 0 2 49% One spray recommended for FAW feeding injury
Cape Elizabeth II 16 0 0 26% 4-day spray interval recommended for all silking corn
Charleston 9 1 0 4% 4-day spray interval recommended for all silking corn
Corinth 2 3 0 0% 6-day spray interval recommended for all silking corn
Dayton I 3 1 1 11% 6-day spray interval recommended for all silking corn
Dayton II 24 0 1 7% 4-day spray interval recommended for all silking corn
Dresden 18 6 1 15% 4-day spray interval recommended for all silking corn
Farmington 1 6 0 2% One spray recommended for ECB on all silking corn
Jefferson 4 0 0 8% 5-day spray interval recommended for all silking corn
Levant 10 4 0 2% 4-day spray interval recommended for all silking corn
Lewiston I 7 0 1 0% 5-day spray interval recommended for all silking corn
Lewiston II 1 2 0 0% No spray recommended
Livermore 3 0 0 8% 6-day spray interval recommended for all silking corn
Monmouth 7 1 0 1% 5-day spray interval recommended for all silking corn
New Gloucester 4 0 5 0% 5-day spray interval recommended for all silking corn
Nobleboro 10 3 1 7% 4-day spray interval recommended for all silking corn
North Berwick 15 2 0 35% 4-day spray interval recommended for all silking corn
Old Town 11 1 0 0% 4-day spray interval recommended for all silking corn
Oxford 1 1 0 0% No spray recommended
Palmyra 3 1 0 2% 6-day spray interval recommended for all silking corn
Poland Spring 1 1 3 16% One spray recommended for FAW on all silking corn
Readfield 1 1 0 3% No spray recommended
Sabattus 5 3 1 0% 5-day spray interval recommended for all silking corn
Wales 1 0 1 0% No spray recommended
Warren 3 2 1 8% 6-day spray interval recommended for all silking corn
Wells I 4 0 0 0% 5-day spray interval recommended for all silking corn
Wells II 0 0 1 13% One spray recommended for FAW + ECB feeding injury

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.

 

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.

 

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.

 

Late Blight:  Grower and Farm Stand Alert

Potato late blight, the disease that caused the significant crop losses for tomatoes and potatoes in Maine last year has just been confirmed at a sight in Waldoboro, and several other suspected sites are now being investigated.  Typical symptoms will be a water-soaked grease spot on foliage with a fine white mycelium on the underside of the leaflet. A stalk infection will usually look dark brown, almost black.

Water-Soaked Spots on Potato Leaf

Late Blight: Water-Soaked Spots on Potato Leaf, photo by Jim Dill

Late Blight on Tomato Leaves

Late Blight on Tomato Leaves, photo by Jim Dill

The spores released by infected plants have the ability to travel 40 plus miles under the right conditions and infect potato and tomato plants.  We are encouraging all commercial growers and home gardeners to be carefully inspecting their plants for disease.  If late blight is found we are asking that the diseased plants be destroyed.  They can be buried or simply bagged so that the spores can not escape and that the plant will die.  Late blight is an obligate parasite and needs living tissue in order to survive.  Applications of protective fungicides should be applied to tomato and potato crops if they have not been receiving regular applications up to this point.

The Pest Management Office in Orono will look at any samples that you may suspect have been infected.  When sending samples, they should be placed in a plastic bag with a piece of dry paper towel to keep the sample fresh.  For pictures of this disease visit the following websites:

www.longislandhort.cornell.edu/vegpath/photos/lateblight_tomato.htm
www.longislandhort.cornell.edu/vegpath/photos/lateblight_potato.htm

The Pest Management Office has copies of a home gardener alert, a late blight ID sheet for roadside stand producers and a poster for late blight identification that you can use to make your help and your customers more aware of this potentially devastating disease.

Please feel free to contact The University of Maine Cooperative Extension Pest Management Office with any questions.

Late Blight Hotline:
For the most recent information, call the IPM Hotline at 207.760.9IPM (207.760.9476).

Pest Management Office
491 College Avenue
Orono, ME  04473
1.800.287.0279
PMO@umext.maine.edu

David T. Handley, Ph.D.
Vegetable & Small Fruit Specialist
University of Maine Cooperative Extension
Highmoor Farm
P.O. Box 179
Monmouth, ME 04259-0179
207.933.2100
Fax 207.933.4647

7-20-2010