Check for spotted wing Drosophila larvae in cherries
Michigan cherry growers with fruit remaining on the trees should look for signs of spotted wing Drosophila larvae.
Although there is little fruit left hanging in sweet and tart cherry orchards, we have found many cherries to be infested with spotted wing Drosophila (SWD) larvae in northwest Michigan. Obviously these fruits will not be harvested, but infested fruit in 2012 could lead to larger SWD populations the following season. We are not recommending that growers apply an insecticide specifically for SWD at this time, but we want to bring awareness about this new insect pest in cherry orchards.
In early infestations, the hole in the fruit is extremely small, almost a pinhole size. Eventually, a dark, circular pattern forms under the hole as the larvae begin to feed on the flesh of the fruit internally. Although we are still investigating these infestations, larger, more jagged holes become apparent as the larvae grow in size. We also believe that the SWD holes and larvae attract sap beetles and some fruit have visible sap beetle feeding around the SWD hole. The following pictures will help growers determine if cherries are infested with SWD larvae.