West central Michigan small fruit update – July 7, 2020

Spotted wing Drosophila are in all berry fields and blueberries are entering the window of susceptibility to its attack. Maintaining an effective monitoring and control program is critical.

Spotted wing Drosophila
Photo by Rufus Isaacs, MSU Entomology

Weather conditions in west central Michigan remain hot with little or no rain at all. Daily average minimum and maximum temperatures for the past seven day were 65 and 90 degrees Fahrenheit, respectively. Rain accumulation during the same period was insignificant continuing with the summer drought period that started more than 10 days ago. According to the Michigan State University Enviroweather extended weather forecast, this weather pattern will remain in place several days more with an increased probability of rain and lower daily temperatures by the end of this week.

Regarding crop conditions, summer strawberry harvest has finished. Fall red raspberries are in the green fruit stage with some summer red and blackberries harvested this week.

Blueberries, on the other hand, are in harvest. Early season varieties such as Weymouth and Duke are hand-harvested in Allegan and Van Buren counties. So far, the major blueberry problem is spotted wing Drosophila (SWD). It arrived in mid-June at blueberry fields and its populations have continued increasing at most monitoring sites in west central Michigan. However, during the past week, we observed a decrease in the number of flies trapped in our monitoring network. We attributed this temporary decline to hot and drought conditions from the past 10 days. According to Rufus Isaacs from MSU Entomology, SWD survival and reproduction potentials is severely affected by high temperatures and low relative humidity (rH).

In support of our blueberry growers, we have continued offering monitoring and technical assistance through our regional SWD monitoring network and online webinars. We would like to continue providing this assistance through educational training materials already available online, and ready to be used by growers to prepare their SWD management programs.

The most important aspect of SWD management and control is to know when and what sprays to use to control SWD efficiently. That includes knowing the type of insecticide to be applied depending on its mode of action and on the impact of current and forecasted weather conditions on its persistence, on and inside the fruit. In addition, information on SWD population provided by an effective SWD monitoring at growers’ own farms (see photo).

Below are the most recent videos produced from training material we developed over the past three years. There you will find the answers to most questions about controlling SWD in an efficient manner. For growers that already attended our face-to-face SWD training programs, these videos will be useful to refresh your knowledge and skills.

Please keep in mind that insecticides mentioned in those videos are not the only ones recommended for SWD. Since the time those videos were produced, new insecticides have been added to the list of products available for SWD management and control. Therefore, we recommend checking the 2020 Michigan Fruit Management Guide (MSU Extension bulletin E154) to obtain an updated list of products and doses.

In addition, you can call your local MSU Extension office or email Carlos Garcia at garcias4@msu.edu or Mark Longstroth at longstr7@msu.edu for assistance with your SWD management program.

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