Michigan spotted wing Drosophila report for Aug. 19, 2016

High risk of infestation of fruit continues to be expected. Susceptible crops must be protected.

This is the Michigan State University Extension spotted wing Drosophila (SWD) Statewide Monitoring Network report. This week, trap numbers and expectations about potential damage from SWD continue to be very high. Out of the 75 traps collected during the week prior to Aug. 18, we captured a total of 2,622 female and 2,651 male SWD for a total of 5,273 SWD flies. We found an average of more than 70 SWD flies per trap and captured them in almost all traps being monitored this week. Ripening fruit throughout the state continue to be at high risk for infestation if not protected including blueberry, grape, peach and raspberry.

With the cooler nights and less extreme daytime heat, SWD populations are expected to keep climbing rapidly. The conditions are highly conducive to its development, and we expect shorter generation times and greater survival of flies with the moist conditions and more moderate temperatures.

The regions that are being monitored for SWD in 2016, how each region is defined (by the counties listed), the number of sites in each region that were monitored this week, the cumulative total of SWD flies caught in traps by region, and the average number of SWD flies caught per trap.

Region

Counties covered in the SWD monitoring network

No. sites this week

Cumulative SWD Total

Avg. SWD flies per trap for the week ending Aug. 18

SE

Genesee, Ingham, Lenawee, Livingston, Macomb, Monroe, Oakland

15

4,448

55.5

SW

Allegan, Berrien, Kalamazoo, Ottawa, Van Buren

35

15,999

96.1

Ridge

Ionia, Kent, Muskegon

5

874

81.2

WC

Mecosta, Oceana

1

202

46

NW

Antrim, Benzie, Grand Traverse, Leelanau, Manistee

18

2,889

34.7

Grand Total:

74

24,412

71.3

Some growers have had a hard time controlling SWD this season. Short application intervals and reapplication after rain events – being sure to check product labels for reapplication restrictions and season maximums – are critical to managing this pest. Check with your local Extension staff or crop consultants and refer to the “2016 Fruit Management Guide” for recommendations for your crop.

SWD Northern LP graph

SWD Southern LP graph

SWD All Sites graph

Bars represent the average number of SWD flies caught in monitoring network traps each week. Dots represent the percent traps that captured SWD that week. The shaded bar across each graph represents the proposed threshold for triggering management of the pest in susceptible crops. Northern L.P. encompasses all network traps in counties north of and including Clare in the Lower Peninsula (n = 18 traps this week). Southern L.P. encompasses all network traps in counties south of Clare in the Lower Peninsula (n = 56 traps this week).

Traps in the network are baited with commercially available lures and placed in susceptible crop fields or orchards – or in a location adjacent to susceptible crops – in areas where SWD infestation has been recorded in the past. Commercial plantings included strawberry, blueberry, raspberry, grape, tart and sweet cherry, peach and plum. Counties included in the 2016 trapping network are Allegan, Antrim, Benzie, Berrien, Genesee, Grand Traverse, Ingham, Ionia, Kalamazoo, Kent, Leelanau, Lenawee, Livingston, Macomb, Manistee, Mecosta, Monroe, Muskegon, Oakland, Oceana, Ottawa and Van Buren.

For the most current recommendations for monitoring this pest, please refer to “Monitoring traps for catching spotted wing Drosophila.” You can find out more about how to identify and manage this pest in fruit crops by visiting MSU’s Spotted Wing Drosophila website.

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