blue berries falling off plump but unripe Plus unusually large number of woody nodules on branches

Asked July 28, 2017, 7:00 PM EDT

I have a tall blueberry bush that has perhaps a dozen or more woody nodule growths at the end of branches where new growth leaves would be expected. This oddity was apparent early while the flowers were still set. Since then, the fruit has been dropping. Plenty of healthy bees, don't start talking pollination, its not a pollination issue. Besides, wouldn't the flower just drop if unpolinated? Seems stupid for a plant to waste energy starting to grow a fruit when unpolinated. Plenty of water. No worms. No maggots. For years yield has been getting better and better year after year, until this year. Not stupid birds tearing them off while still green, plant is netted.. The fruit is plump and healthy looking but falls off, its on the ground under the plant. The odd woody growths screams disease to me. WHAT IS IT AND HOW IS IT TREATED? Left image shows a small nodule, a fruit that has fallen and another that has not yet fallen. Right image shows a large nodule. There are no insects or worms in the nodules. They look like the plant equivalent of a cancerous growth.

Suffolk County New York

3 Responses

The problem with your plants appears to be blueberry stem gall wasps. They cause these ovoid to kidney shaped swellings on blueberry stems after eggs are deposited in the stem. Early galls are green and become brown and woody as they age.

Here is a Cornell Extension blog post that covers this pest. It is important to remove these galls from your plants as soon as you see them. Here is additional information on control from Michigan State University which has been studying the increase in infestations.

All of my galls at at the extreme end of branches where there would normally be new growth. The wasps I imagine might on occasion randomly choose to lay eggs at the extreme end of a branch, but every time seems unlikely. Careful dissection of several galls revealed no larva within. I've saved a few to incubate and torture to death once they hatch, then incinerate ... if anything hatches, but I see no evidence that anything is going to hatch. Do the eggs not hatch until after winter? Must they over-winter first? Everything online suggests otherwise. The link you provided says the larva should grow during the summer, pupate over winter and hatch as an adult in the spring. There are no larva in my galls unless they are so small they must be observed by microscope. Are there any other options that would account for the placement and lack of larva?

We recommend you contact the Cornell Cooperative Extension for Suffolk County. Their Horticultural Diagnostic Lab should be able to examine your plant materials and provide you with an answer.

Cornell Cooperative Extension -Suffolk County


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