SWD Found in Blueberries and Cherries in Maryland

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

A few blueberry and cherry growers in central Maryland have reported fruit damage to their crop from Spotted Wing Drosophila (SWD) this week. If you grow any small fruit such as blueberries, cherries, blackberries, raspberries it would be best if you check these crops for the presence of SWD. This is earlier than we usually see damage from this pest, but it is not totally unexpected. In New York over the years they have been finding SWD earlier and earlier in their traps throughout the state, with many locations recovering SWD throughout June. If you have had problems in the past with SWD and you are not using traps to monitor them and your blueberries are turning from green to purple you should probably think about going on a spray program if you have not already.

Cherry fruit with SWD oviposition sting, exit hole of maggot and the maggot

Figure 1. Cherry fruit with SWD oviposition sting (white arrow), exit hole of maggot (yellow arrow) and the maggot (green arrow).

The damage starts with the female fly cutting a slit into ripening fruit with her serrated ovipositor, this later looks like a “sting” in the berry (Fig. 1). Maggots will then feed by tearing and shredding the interior of the fruit often causing a softened collapsed brown area (Fig. 2). When ready to pupate the maggot will exit the fruit causing an exit hole (Fig. 1), which can allow entry of microorganisms that cause rot. Fruit should be examined very carefully for any of these signs of SWD presence. Be sure to rotate between materials of different chemical classes to slow the development of pesticide resistance.

Brown collapsed area on cherry fruit due to SWD maggot feeding.

Figure 2. Brown collapsed area on cherry fruit due to SWD maggot feeding.

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