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Spotted Wing Drosophila Update: 10/17/2014

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Click on photo to enlarge.

David Handley, Vegetable and Small Fruit Specialist; James Dill, Pest Management Specialist; Frank Drummond, Professor of Insect Ecology/Entomology

Male and Female Spotted Wing Drosophila Flies

Male (left) and Female (right) Spotted Wing Drosophila, photo by Griffin Dill. Actual size: 2-3 mm.

We have been anticipating a rapid increase in spotted wing drosophila trap captures since late August, based on our experience over the past two seasons, and it appears that we are now seeing it in at least some locations. The highest fly counts of the season occurred this week at sites where we have been seeing numbers rising over the past several weeks, including Wells, Cape Elizabeth, Dresden and, most notably, Warren. It should be noted, however, that the trap in Warren was placed close to a waste pile of rotten fruit where flies were abundant; although, until this week, most of the fruit flies caught at that site were species other than spotted wing drosophila. Not all trap sites have been experiencing a significant rise in fly counts, and some have remained at surprisingly low and stable levels. This is probably due to a combination of localized conditions, such as availability of food and lack of moisture, which could limit their ability to reproduce. At sites where drosophila populations are high, they will probably continue to increase until we have several hard frosts, and/or available food is depleted. Most farms have called an end to their berry season and have stopped spraying. There are still a few that are taking advantage of this warm fall and continue to harvest fall raspberries and late blueberries. These crops will need to continue to be sprayed until harvest is complete to protect against drosophila infestation.

This is our last regularly scheduled update for spotted wing drosophila for the 2014 season. We will update our website with any new information on spotted wing drosophila and management as it becomes available. I’d like to thank all of the farms that helped us with trapping this year, and express my appreciation to the people who helped maintain the traps and count all those flies, including Ben Woodman, Christina Hillier, Kara Rowley, Tammy Cushman and Pat McManus. We hope to monitor spotted wing drosophila populations around the state again next year to keep growers informed about this threat and to better understand how to manage it.

Town Spotted Wing Drosophila weekly trap catch 10/17/14 Spotted Wing Drosophila weekly trap catch 10/10/14 Spotted Wing Drosophila weekly trap catch 10/3/14 Spotted Wing Drosophila weekly trap catch 9/26/14
Limington 128 127 48 6
Limerick 859 346 141 195
Wells 18,928 6,064 558 523
Cape Elizabeth 1,722 684 417 401
Bowdoinham 181 106 46 25
Dresden 6,872 3,075 739 599
Warren 50,848 620 211 128
Farmington 10 17 29 23
Livermore Falls 16 12 28 5
Mechanic Falls 70 15 33 20
Poland Spring 544 1,171 2,118 604
Monmouth 329 66 24 23
Wales 200 123 215 67
Old Town * 29 13
Levant * 43 31 30

*We’ll update the information for this site as soon as we have finished counting the trap catch.

Based on what we know so far about this pest, here again are our six rules for managing spotted wing drosophila.

  1. Monitor for the flies with traps, and for the larvae in fruit.
  2. Spray regularly and often once flies have been found in the field (1-2/week).
  3. Harvest fruit regularly and often; do not leave any ripe/rotten fruit in the field.
  4. Sort fruit at harvest; do not leave any soft fruit in the container to be sold.
  5. Chill all fruit immediately after harvest to 38ºF (or as close as you can) for at least 12 hours to slow development of any eggs or larvae.
  6. Prune the planting to open up the canopy and create dry, light conditions.

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

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