cherry tree mold/worms

Asked January 18, 2013, 12:56 PM EST

We have an 8-year-old Stella cherry tree in our backyard. It produced good fruit yields for its first four years. For the past few years the fruit begins to ripen, and then as soon as it ripens a mold takes over and makes the fruit soft and unappealing. Also, when we cut into the cherries, we often find a small grey worm against the pit. We have used dormant sprays in the past, but they do not seem to take care of the problem. Any recommendations?

Multnomah County Oregon fruits and vegetables insect issues horticulture

1 Response

Thank you for your question to Ask an Expert about your Stella cherry tree. The damage you are describing is consistent with an infestation of the spotted wing fruit fly (SWD). This relatively new pest attacks fruit just as it ripens; symptoms include mold, wrinkling and softening of the fruit followed by the larvae emerging from the berries. Unfortunately dormant sprays will not prevent SWD infestations.
The public is encouraged to report infestations but only after the critters in the fruit are verified as SWD by raising the adult flies from the infested fruits. Since it's unlikely you have any infested fruit at this time of year, you can start by doing a couple of things: first educate yourself about SWD and its management, then begin to apply those management practices, and monitor for the presence of flies later this year. You'll find information about SWD in this publication: Protecting Garden Fruits from Spotted Wing Drosophila http://horticulture.oregonstate.edu/system/files/em9026_0.pdfYou’ll find additional information at the official SWD site http://horticulture.oregonstate.edu/group/spotted-wing-drosophila. Once you arrive at the main page, click on “Noncommercial/Gardeners" on the right side of the page. Read the documents and view the high-quality images and brief how-to videos.The bottom line for SWD management is that it requires a combination of various tactics:
1. Sanitation – Collect infested fruits (on the tree, vine, canes or ground) whenever you see them; place in a securely closed plastic bag then set in the sun for at least 6 hours.
2. Exclusion - Net the fruit, entirely or in part with inexpensive tulle (fabric for wedding veils)
3. Harvest promptly; better yet, a bit early
4. Trap – You can easily make traps from materials you likely have at hand which will help reduce the population as it can grow at a mind boggling rate. The best baits are either apple cider vinegar or white wine. (Regular white vinegar doesn’t work.) The SWD page has the specifics, as well as brief videos for making traps; placing traps; and more.
5. Pesticides, organic or not, are considered a last resort. Active ingredients available to home gardeners are listed in the above linked document. When using pesticides of any sort, always follow the label’s directions exactly.
If you have suspected infected cherries this year, please bring some samples to Multnomah County Master Gardener office, Montgomery Park, 2701 NW Vaughn St., Suite 450, Portland, OR 97210; Phone: 503–445–4608; Hours: 10 AM – 2 PM, Monday – Friday. Thank you for your inquiry. If you have further questions, please ask.