Michigan spotted wing Drosophila report for June 27, 2017

Another jump was seen in flies caught in monitoring traps. Ripening sweet and tart cherries and early ripening blueberry cultivars are vulnerable. Monitoring for this pest is critical as crops become susceptible.

Fruit ripening at different stages on a single cherry tree are susceptible to spotted wing Drosophila infestation. Photo by Julianna Wilson, MSU.

Fruit ripening at different stages on a single cherry tree are susceptible to spotted wing Drosophila infestation. Photo by Julianna Wilson, MSU.

Michigan State University Extension fruit team members continue to monitor for spotted wing Drosophila (SWD) across the fruit producing regions of Michigan with more than 100 traps set up in susceptible crops or non-crop hosts.

Earlier than usual activity of SWD continues this season. This likely reflects our mild winter and the high population last fall, combined with our spring conditions that provided an early start to the fly activity. SWD pressure is strong this season and growers of susceptible fruit should be prepared to manage this insect through their harvest season.

In the past week, about 40 percent of all the traps are catching adult SWD flies, with an average of just over two SWD flies per trap and a total of 296 SWD flies (up from 182 last week) caught in 52 out of 120 traps. There were 169 SWD flies caught in the 43 traps reporting from the southwest region, 64 SWD flies caught in the 10 traps reporting from the southeast region, 38 SWD flies caught in the 20 traps reporting from the west central region, and 25 SWD flies caught in traps reporting from the northwest region.

Traps that have been catching SWD flies so far this season are placed in blueberry (Allegan, Ottawa and Van Buren counties), sweet cherry (Kent, Lenawee and Macomb counties), tart cherry (Allegan, Antrim, Benzie, Berrien, Grand Traverse, Kent, Leelanau, Mason, Monroe, Oceana and Van Buren counties), grape (Berrien, Ionia and Van Buren counties), peach (Allegan and Berrien counties), plum (Van Buren County), raspberry (Ingham and Kent counties) and strawberry (Macomb and Livingston counties) blocks.

Ripening fruit in these counties may be at risk of infestation by this pest. Growers of June bearing strawberries, early ripening blueberries, sweet and tart cherries should be monitoring for this pest in traps and in their fruit.

In addition, ripe cherries are present on the ground in tart cherry orchards in southwest Michigan. SWD have begun to emerge from fruit collected from the ground and held in the laboratory for a week. The early detection of SWD this season and the potential for oviposition in the ripe cherries makes it especially important for cherry growers to keep orchards covered for SWD, and to not allow gaps in coverage. Preventing infestation will require a seven-day spray interval with highly effective materials and excellent coverage.

As the early blueberry varieties such as Duke come into harvest this week, those blocks should be protected if SWD has been detected in the area. The next ripening varieties such as Bluecrop are starting to color and once those start to show some ripening those also need to be protected. Later cultivars with berries that are still green and hard do not need protection until they start to ripen.

Summer raspberries are starting to ripen too and bearing plantings require protection to reduce SWD infestation. Frequent harvesting can also help growers keep ahead of this pest in summer and fall raspberries.

Counties included in the 2017 trapping network are Allegan, Antrim, Benzie, Berrien, Grand Traverse, Ingham, Ionia, Kent, Leelanau, Lenawee, Livingston, Macomb, Manistee, Mason, Mecosta, Monroe, Montcalm, Muskegon, Oceana, Ottawa and Van Buren.

All 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. The majority of the traps this season are standard deli cup style traps baited with the commercial Scentry brand lure. Most of the traps are placed in areas where SWD infestation has been recorded in the past.

For more information on this pest, including how to identify, monitor and manage this pest in fruit crops, please visit the MSU Spotted Wing Drosophila webpage.

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