Some kind of blight on Sour Cherry Trees

Asked June 4, 2020, 11:02 AM EDT

My sour cherry trees are having a problem. I've got loads of fruit, but they are getting some kind of blight or disease. This happened last year, and wiped out the whole crop. The tree themselves seems to be fine, just the fruit is affected. It starts off as tiny brown spots, then the spots grow and eventually consume the fruit. Help!! What is it and what, if anything, can I do about it? Pics attached. Thanks in advance!

Hennepin County Minnesota

3 Responses

The fruits shown in the photos appear to have been damaged by plum curculios, cherry curculios or both. These tiny weevils are capable of eliminating several kinds of fruit crops including cherries. Some of the fruits in your photos show horseshoe-shaped scars typical of plum curculios.

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Thank you - that helps!

I'm not an experienced gardener, I need a little more layman's terms help to proceed.

Is it too late to save this years cherries?

And specifically - what, if anything, can I spray to control theses weevils?

It might be too late to save this year's crop but with the following information from a University of Kentucky bulletin you should be able to reduce, though perhaps not eliminate, the damage next year.

"Adults control is accomplished by insecticide applications timed at the petal-fall and/or first-cover stage for apples, and the shuck-split and first-cover stages in peaches and cherries. Serious plum curculio damage is usually restricted to orchards that do not use an insecticide application that is effective against plum curculio in this period. To improve timing, commercial growers can use a beat sheet to monitor for the adults, or monitor for the first signs of curculio damage to the fruit. Generally, the adults begin to damage the fruit when the night time low temperatures begin to reach 60°F."

To determine if/when curculios are present, spread a white sheet or similar cloth under the tree. Shake branches vigorously. If the weevils are there, some will fall onto the sheet.

Insecticides labeled for use against plum curculio, and available for homeowners include carbaryl (Sevin), malathion and kaolin clay (Surround).