West central Michigan small fruit update– June 29, 2021

Blueberries started ripening in west central Michigan, but spotted wing Drosophila has arrived too.

Flowchart graph
Flowchart to make decisions on when to spray against spotted wing Drosophila and what class of insecticide utilize based on their behavior at different conditions of rain and temperature. Photo by Carlos Garcia-Salazar, MSU Extension.

Fruit ripening is already in progress in west central Michigan and strawberries, raspberries and blueberries are already in harvest or near harvest. The hot and dry weather conditions that prevailed during most of the springtime accelerated fruit ripening. However, in strawberries, fruit size was affected by spring frosts followed by high heat and dry weather conditions during the fruit growing period. In addition, the rains from the past days cut short the harvest season because ripe fruit started decaying in the field. Strawberry growers will start renovating those field soon.

Regarding red summer raspberries, some fruit has been already harvested but the pick of the harvest will come at mid-July. Blueberries, on the other hand, began to ripen. Early varieties like Duke and Bluecrop are already with 10 to 15% with fruit in the blue stage at west central Michigan, but in southwest counties the harvest of early season varieties will start this week.

With the beginning of the blueberry harvest and with the presence of spotted wing Drosophila (SWD) that has already being detected in ripening varieties, the need for protection against this pest has also began. The key for maintaining control with SWD is to start chemical control as soon as the first flies are detected in your field. That will delay the population build-up to levels difficult of controlling at mid-summer.

The recommendation is to initiate the insecticide applications when the fruit is changing color and the field is with 5% or more of the fruit already in the blue stage, and you have detected the SWD in your traps. If you are days away from harvest, use a broad-spectrum insecticide with penetration capability inside of the fruit, such as Lannate, Imidan, etc., that will target adults, eggs and larvae already inside of the fruit. That will delay the buildup of the SWD population. You may also use Mustang Maxx or any other pyrethroid insecticide that remains attached to the waxy fruit cuticle and is not easy of being washed off from the fruit if rain occurs after the application. Check the Michigan State University Extension Bulletin E0154, 2021 Michigan Fruit Management Guide, for the best options.

Above is a flowchart with some guidelines for managing SWD in blueberries. It utilizes the information on the presence of SWD, the fruit coloring stage, the weather conditions at the time of the application and the suggested insecticides based on the behavior for SWD management. Insecticides in this flowchart are those for which we have research information at MSU Extension. Check the 2021 Michigan Fruit Management Guide for more recommended insecticides.

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