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Cooperative Extension: Maine Wild Blueberries

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SWD Update from Frank Drummond – August 19,2014

Last week (Aug 19th) SWD trap captures in both the Blue Hill and Jonesboro area remained stable with little change in adult captures compared to the previous week (Blue Hill = 10-20 flies/trap; Jonesboro = 4-6 flies/trap).  As of last week we have not detected any SWD in fruit samples. We will be sampling the traps and fruit again early this week (Aug 26) and let you know what we are finding.  We suspect that fruit infestation will start to occur fairly soon, at least in the Blue Hill area. If you have not harvested your fields yet, please maintain your SWD trapping program.

Please contact David Yarborough or Frank Drummond if you any questions and/or concerns.


SWD Update from Frank Drummond – August 18, 2014

Last week (Aug 13th) SWD trap captures in the Blue Hill area started to increase dramatically to 10-20 flies/trap. In the Columbus and Jonesboro area trap capture increased to 4-6 SWD/trap. As of last week there was still NO detectable SWD larval infestations in the fruit. We will be sampling the traps and fruit again early this week (Aug 19-20) and let you know what we are finding. We suspect that fruit infestation will start to occur fairly soon, at least in the Blue Hill area. If you have not harvested your fields yet, please maintain your SWD trapping program.

Looking for samples of Exobasidium on leaves and fruit

I am looking for some samples of a fungus that attacks leaves and fruit and produces round, white to pale green spots on the leaves and fruit.  When the leaf spots get old they can turn red, but will have white areas under the leaf.  This fungus will also produce white spots on fruit.   This fungus does not seem to be a large problem in Maine.  I am interested in collecting samples for a colleague who is trying to clearly identify this fungus so we will have a better idea of how to control it.

If you see this fungus in your field, please let me know. Thank you, Seanna Annis 207-581-2621 or

Image Description: Round white spots caused by Exobasidium on leaves of rabbit eye blueberries, spots on wild blueberry leaves will be about 1/4 to 1/2" across

Image Description: Exobasidium on wild blueberry fruit

It is time to put out your mummy berry plots for next year

This is a good time to collect mummy berries from your plants to put out in mummy berry plots for next year. The mummy berries are easy to see before harvest since they are grey and shriveled compared to the blueberries.  The clones vary in the number of mummy berries they produce so you may need to look at a few places in your field for enough mummy berries for your plots.  Typically if you see a few mummy berries still on the plant you will find 4 to 10 times as many fallen to the ground under those plants.  You will need about 150 mummy berries  in total if you put out 3 plots (50 mummies per plot).  You can also collect mummy berries from processing lines  if you see them then.   Please see below for instructions on how to put mummy berry plots.

We are looking for growers who are willing to check their mummy berry plots twice a week and report to me on the development of the mummy berry cups. We want to place our weather stations in fields with monitored mummy berry plots next year. Please let me know if you would be willing to put out a mummy berry plot and have a weather station in your field.

If you are willing to have a weather stations and monitor plots, but do not have the experience to put out mummy berry plots, we can help you set up the plots.  Please contact Seanna Annis at 207-581-2621 or via email at if you are willing to be a monitor of mummy berry next year OR have any questions.

How to put out Mummy berry plots

1. Collect about 150 mummy berries (50 for each mummy berry plot) from your crop field(s) near  harvest (or from the process line or winnow piles if you have them). The mummy berries will be whitish grey and smaller than the berries and will have dropped onto the surface of the leaf litter under the plants, typically where you s still see some amongst clusters of healthy berries on stems.  Often clones produce different amount of mummy berries, so if there are no mummy berries in one spot, try another area in your field. Often there are more mummy berries at the edges of fields.
2.As soon as possible after you have collected the mummy berries, put them out in the field you will be monitoring.  In next year’s crop field, choose 3 areas within your blueberry field. I suggest 3 areas because some years  one of our plots has not worked in a field.  Each area should be about 3” by 3” that is clear of stems but amongst the plants. Choose areas that look like they have damp soil most of the time AND will be easy for you to access next spring. These areas do not need to be widely spread around the field, 5 to 10 ft between each one will be fine. If you have different exposures, soil types or large shaded areas in your field you may want to place your mummy berry plots around your field to get the full range of when the mummy berries develop. The areas should not be on slopes where the mummy berries will be washed away, in hollows where they will be water-logged or in areas with lots of frost-heaves.
3. In each 3″ by 3″ area, clear off the leaf litter to one side and scrape off about 1/4” of hard packed soil and put aside. Place about 50 mummy berries on the surface of the soil and press the mummy berries firmly into the soil (with your fingers or step on them).  The mummy berries need to be buried in soil but not more than 1/2” deep at most.  Cover the mummy berries with a small amount of dirt (1/4”) on top and press them firmly down again. You should NOT be able to see the mummy berries. Replace the leaf litter over the mummy berries to provide protection over the winter.

4. VERY IMPORTANT: Stake or flag the plots on either side so you can locate them in the spring.  Two stakes or flags makes it much easier to figure out where to look in the spring.

Questions: Contact Seanna Annis at 207-581-2621 or

Image Description: mummy berry

Image Description: 50 mummy berries before being covered by soil; 3 inches

SWD Update from Frank Drummond – August 13, 2014

SWD adults are still being trapped in single numbers. This suggests that the population has not started to build yet, although it is anticipated that this might occur in the next 7-10 days.  As of yet, we have NOT yet found any wild blueberry fields that have SWD infested berries, although blueberry maggots have been found in fruit.  Most of our sampling has been from Stockton Springs to the Downeast area. Our recommendation is to be vigilant and continue to monitor traps, harvest fields as soon as you can, and protect those crops that will not be harvested for some time providing that SWD has been found in traps in those fields. There are still some fields that have NOT detected SWD yet.

SWD Update from Frank Drummond – July 28, 2014

Last week we captured SWD in traps that were placed in Jonesboro. So far, SWD has been captured in a few fields in Coastal Maine, the Blue Hill area and in Jonesboro. SWD was also captured in Nova Scotia last week. Please deploy traps if you have not already done so and monitor them at least on a weekly basis. If you capture a male SWD, protect your crop with an insecticide. (see the SWD ID factsheet on the wild blueberry website:

SWD Detected in Parts of Southern and Downeast Maine

The spotted wing drosophila is starting to be detected in both southern and parts of downeast Maine. David Handley, who has been sampling highbush blueberry and raspberry fields has reported trap captures of spotted wing drosophila in Cape Elizabeth, Buxton, Turner and Wales. In wild blueberry fields MALE SWD have been captured in Blue Hill and Sedgewick. It is typical in the early season (from what we have observed in the first two years) that initial trap captures are quite spotty. Our recommendation is that if your crop is vulnerable (containing ripe fruit) and if you have NOT put traps out yet…you should put out traps as SOON as possible. Inspect the traps 2 times per week for males (spots on wings..see the wild blueberry factsheet on SWD Biology). IF a male is captured then it is time to protect the crop with an insecticide (see wild blueberry factsheet on insecticides suitable for SWD).

It is doubtful that any fruit has been attacked by SWD yet. We will be sampling the fruit in fields this week where SWD has been captured and let you know what we find.

SWD Management Recommendations Fact Sheet

Attached is a fact sheet for SWD management in Michigan Highbush bluberries (SWD Management for Michigan Blueberries_June 21 2014) , which is very informative and includes a table with rain steadfast properties of some of the SWD insecticides.

Here is the link to the the SWD Management for Michigan Blueberries

Some reports of Botrytis blossom blight and Frost – June 6

There have been some reports of localized patchy frost damage the last week of May followed by Botrytis symptoms showing up this week.  Frost will make blossoms more susceptible to Botrytis infection.  I have heard this from growers in the Union area and around the Orland area.   In one field, we saw low levels of both frost and Botrytis infection on the blossoms.   One of the differences to previous years was the very short hairs of the Botrytis sticking out of the base of infected blossoms.  A hand lens will be needed to see this kind of Botrytis infection.   Please look at previous reports to see pictures of these different diseases. 

The rain over the last 2 days, Wednesday June 4 to Friday June 6th produced moderate to high risk of Botrytis infection across monitored blueberry areas.   Many growers are nearing the end of bloom, so there is little risk of further Botrytis infection that will impact the crop.  

Image Description: Botrytis with short hairs

Frost and Botrytis risk in some areas May 29th


In Northern Hancock at our Silsby Plains site and at our Deblois and Cherryfield weather station locations in Washington county, there were frost conditions overnight from Wed. May 28th to Thurs. May 29th.  Lee Beers is a PhD student studying cold tolerance in blueberries and his research has found conditions from 28 F to 24 F will cause some minor damage to flowers but temperatures below 24F will kill many flowers.  Temperatures at Cherryfield dipped to at least 26 F and at Deblois and Silsby Plains to dipped to 22 F for a number of hours.    All of the other weather station locations had temperatures above 30 F overnight.

Botrytis Risk

Two weather station locations, Dresden Mills and West Rockport reported weather conditions that produce a high risk of Botrytis infections, IF the fungus is present in a field.   This does not mean fields will get Botrytis, just that there is a risk of infection if the fungus is present.

Fields with mummy berry disease will also have killed blossoms, so please look at the symptoms to determine what has killed your blossoms.  Please take a look at previous blog posts or emails  for pictures and descriptions of the symptoms for Mummy berry blight, Botrytis blossom blight, and frost.

  Any questions please call Seanna Annis  1-800-897-0757 (Maine only), or email at


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University of Maine Cooperative Extension

Contact Information

Cooperative Extension: Maine Wild Blueberries
5741 Libby Hall
Orono, Maine 04469-5741
Phone: 207.581.3188, 800.287.0274 (in Maine) or 800.287.8957 (TDD)E-mail:
The University of Maine
Orono, Maine 04469
A Member of the University of Maine System