MSU Extension

Spotted wing Drosophila (SWD) has arrived on small fruit crop fields including blueberries. This past week, we found the first SWD females in Allegan County in blueberry fields with a previous history of SWD infestations. The early detection of the beginning of SWD activity is of critical importance to help growers prepare their integrated pest management (IPM) program to be ready to deal with this pest in a timely manner.

Current weather conditions in west central Michigan are accelerating plant growth and development in all fruit crops. Berry crops have been favored for these good weather conditions and ripening in crops like strawberries are progression without major problems. Blueberries, on the other hand, are still in the green fruit stage with early varieties entering the coloring stage in fields located south of Allegan County. So far, given the prevailing weather conditions, the ripening is expected to proceed at a normal rate with an expected harvest time for the first weeks of July.

Presently, there are some problems affecting strawberries and blueberries that are related to insect pest problems.

In strawberries, although the crop has been abundant without major incidents, there are some problems associated to the presence of the strawberry root weevil Otiorhynchus spp. This insect is causing some damage in strawberry fields and creating economic losses for growers. Management of this insect is difficult because its lifecycle is mostly in the ground or in the roots of the plant where insecticides are difficult to reach. However, the most effective treatment is application of insecticides at the time when the adults are exposed and are found feeding on the strawberry foliage. Recommended chemical control includes foliar applications of Lorsban, Sevin and Brigade, and Platinum as soil application. These recommendations are based on research conducted at Michigan State University Extension (see bulletin E-154 “2013 Michigan Fruit Management Guide”) and on research conducted by Celeste Welty from Ohio State University.

Cultural control is another tool that can be used in combination with chemical control. Some of the recommendations are plowing and rototilling the soil to expose weevils to bird predation and crop rotation with clover, alfalfa or corn. These practices will help to reduce the weevil populations. For more information, see the Strawberry Root Weevil page from Oregon State University.

In blueberries, SWD specimens have been trapped in conventional traps loaded with a bait of yeast and sugar and placed at the edge of blueberry fields near woods. This early detection will help us modify our IPM program to incorporate SWD control.

In addition to SWD, some fields are experiencing fruitworm problems. This past week we found fruit damage in blueberry fields that missed the first application against fruitworms or their control was inefficient. A major problem that might be the cause of fruitworm control failure is pheromone trap placement and servicing. In some of the fields where fruitworm damage had been found, pheromone traps were deployed, but no fruitworm moths were trapped. Based on these trap reports, growers delayed the insecticide application with the expected consequences: fruitworm infestation.

Upon examining the traps, we found that the lures were placed on top of the tangle foot and completely covered by this. The placement of lures on the tangle foot is a bad practice because the lure gets covered with this sticky material and it makes it impossible to release the pheromone it contains. The result is that the trap fails to detect the flying populations of moths that it is supposed to detect.

Another possible reason for this fruitworm outbreak could be the sudden emergence of a new peak of adult cranberry fruitworm that occurred during the previous week. That sudden emergence of fruitworms created problems for growers that were not expecting another fruitworm flight. This may have contributed to some of the unexpected damage we are observing. Therefore, our recommendation is that growers need to verify their pheromone traps were correctly serviced and that no fruitworm egglaying occurred after the last flight of cranberry fruitworm moths. If damage is found, a rescue application might be needed. One possible insecticide that may have an effect on fruitworm larvae already inside of the fruit could be Imidan. Some of the research conducted at the Trevor Nichols Research Center by John Wise has shown that Imidan can penetrate deep into the fruit, killing fruitworms already inside the fruit.

If you have questions regarding the effectiveness of your fruitworm control or how to prepare for the SWD control season, please contact your local MSU Extension county office or contact Carlos García at 616-260-0671 or garcias4@msu.edu.