When should I spray my cherries? - Ask Extension
I have two sour cherry trees that have had worms in the fruit the past two years. Following the U of M Extension advice, I put out apple cider vinegar...
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When should I spray my cherries? #576101
Asked July 01, 2019, 10:30 PM EDT
I have two sour cherry trees that have had worms in the fruit the past two years. Following the U of M Extension advice, I put out apple cider vinegar traps and a yellow card, but have not identified the target insects among those that they have captured (spotted wing drosophila and the cherry fruit fly; identifying drosophila in the vinegar is near impossible.) The cherries are starting to turn red. Should I just spray anyway since I know the insects must be around? (I plan on using a spray with spinosad.) If so, when do I do it? Thanks.
Hennepin County Minnesota
Expert Response
Hello. I'm glad you've turned to AaEx.
You seem to be doing all the right things and this is a very good question. I'm wondering if you haven't seen SWD (spotted wing dropsophila) and you've changed the vinegar trap weekly, maybe they haven't been around. This spring has been cool and wet though I don't know if that has an effect on SWD.
The material I'm reading about spraying for SWD from the U of MN Extension says "the best control appears to be when gardeners destroy infested fruit to kill larvae, while using an insecticide to kill the adults at the same time." It also indicates to spray in the evenings when beneficial insects are less likely to be around and harmed.
I assume you're monitoring the yellow sticky cards for the cherry fruit fly. Here is what I've found in the U of MN Extension literature about when to spray for cherry fruit fly:
Adult cherry fruit flies emerge one to two weeks before they start depositing eggs. The first insecticide should be applied as soon as the first adults are caught on sticky cards. If necessary, a second spray can be applied ten days later. Insecticides that can be used to control cherry fruit fly are acetamiprid, carbaryl, malathion and spinosad.
Here is a link to the pdf from the U of MN Extension on pest management for home stone fruit trees that I used in this message: https://conservancy.umn.edu/bitstream/handle/11299/198102/Stone%20Fruit%20Home%20IPM.pdf?sequence=1&...
I hope this information helps.
Okay, but what if the target insects don't show up or I fail to identify it? I know we have had worms (last year was much worse than the year before), and I expect they will be back this year. How do you determine when to spray in those circumstances?
Hello,
Well I guess you could spray but the information we have doesn't cover that contingency. Obviously if you start seeing cherry fruit flies in the yellow traps, spraying them with a pesticide that covers both SWD and the fruit flies takes care of two birds with one stone.
Another thing to think about is if you were diligent in destroying affected fruit last year, then maybe the possibility of SWD is low for you this year. At any rate, here is what the U of MN Extension states about that prevention step to keep the population down for later fruit this year and certainly for next year:
I hope this information helps.Remove and dispose of all infested fruit to keep SWD numbers low. The larvae can be killed by microwaving the fruit, cooking the fruit or placing the fruit in a sealed plastic bag that will be put in the trash. Do not bury infested fruit or place fruit in a compost pile as the adults can still emerge.
