Flies Spoiling Your Cherry Season?

As cherries begin to ripen on backyard fruit trees, you'll want to monitor the fruit for pests, especially an invasive species called the spotted wing drosophila (Drosophila suzukii).

The spotted wing drosophila (SWD) is a new pest to California (since 2008). It's a small fly that attacks ripening cherries, and may also attack ripening raspberry, blackberry, blueberry, and strawberry crops, especially in coastal areas. When conditions are right, the fly can also attack soft-fleshed fruit such as plums, plumcots, nectarines, and figs.

If your cherry tree has SWD, you might notice that fruit flesh has one or more small punctures or “stings” on the surface. These symptoms are evidence of the eggs laid by the female SWD. Eggs will hatch into larvae (maggots) which feed inside on the fruit, causing brown and soft sunken areas that may exude fluid.

To determine whether you have SWD and not other vinegar flies, which attack only rotting or fermented fruit, you can make a simple apple cider vinegar trap. This will help you trap and identify the male SWD's, which have dark spots on the tips of their wings.

If you notice SWD in your fruit early enough, you can save some of the crop by harvesting it immediately and removing fruit with stings on the surface. Put infested fruit in a sturdy, sealed plastic bag and dispose of it in the trash. If you have fruit that isn't ripe yet, place fine netting around it to protect it.

Unfortunately, in many cases by the time you notice SWD damage, it may be too late. For information on how to make an apple cider vinegar trap and how to protect your fruit next season, see the UC IPM Pest Note: Spotted Wing Drosophila.

If your cherry tree has a different pest or problem, visit the UC IPM Cherries page to see a list of other pests, including diseases and environmental disorders.