I have had great harvests from my sour cherry tree for the last 4 years. This year the fruit has black spots/streaks. I haven’t been able to see any larvae or insects on the tree and google was not particularly helpful. I would appreciate ideas on what might be causing the problem. Thank you!
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Hi Kelly, would you be able to post a photo? We can then send your query to the Vancouver Island Master Gardeners.
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Post edited with the picture. A bit of an adventure to take that pic… thanks for you help!
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Many thanks to Milner Gardens & Woodland’s Gardening Advice line (a partnership between Vancouver Island University’s Milner Gardens & Woodland and the Vancouver Island Master Gardeners Association) for the following response:
Based on the information provided, it is a bit difficult to tell what exactly might be happening. The discolouration appears to be some form of cellular damage; whether it is superficial or perhaps deeper is hard to tell. To gain a better understanding of the issue, we need to ask the following questions:
How much fruit is affected?
Are the affected fruit localized to any particular side or area of the tree? This could help rule out abiotic caused like sun damage or some type of bruising caused by mechanical damage(?) which would mean the problem is more cosmetic.
Were there any problems (i.e. browning or grey molding) with the blossoms in spring? Any current problems with the branches or leaves? This could indicate the fruit has been affected by brown rot spores (Monilinia fructicola).
If she opens the fruit, are there any insect larvae? This could be a giveaway for spotted wing drosophila larva. I suspect it isn’t Western cherry fruit fly larva (Rhagoletis indifferens) because they feed around the stone and cause little to no visible damage until the mature larvae exit the fruit in late to mid-July.
Initial suspicions indicate this might be brown rot (Monilinia fructicola), but we would need more information to confirm that. To recap, based on the photo alone, the cause of the discolouration could be a few different things, but more information would be needed to help come to a conclusion:
Biotic factors:
Brown rot (Monilinia fructicola)
Spotted wing drosophila larvae
Brown Marmorated stink bug feeding
Abiotic factors:
Cosmetic blemish
Sun damage
Sources:
https://hortsense.cahnrs.wsu.edu/fact-sheet/cherry-brown-marmorated-stink-bug/
Heidi and Diane
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My sincere thanks Heidi and Diane. Some additional information.
- all the fruit is affected. Unripe and ripe all have the same spots. As the fruit ripens it can become a bit more noticeable but that could be due partially to the change in colour and it going somewhat transparent when ripe
- I can see no larvae of any kind. I have some cherry maggot in my sweet cherry so I know what that looks like. I have soaked the fruit as well and not any sign of larvae.
- I saw no discolouration on leaves and the flowers were fine in spring.
- There doesn’t seem to be any fruit that is shrivelling or has something more indicative of fungus.
I have seen stink bugs (they are everywhere) but it hasn’t been more than the one or two that I normally see.
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More info from VIMGA:
Based on the additional information, we suspect the discoloration may be caused by an abiotic factors, likely wind causing the fruits to rub together or slight sun damage caused by sudden sun or heat intensity. Both of these factors can cause superficial darker “brown” spots on the epidermis (skin), however, It would be best to open the fruit and determine if and how far the discoloration extends into the flesh.
Sources:
https://www.tomra.com/food/media-center/tomra-food-defect-glossary/cherry-defects-and-blemishes
Heidi & Diane
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