Blueberry damage could be plum curculio, Reduced production of strawberries - Indiana Yard and Garden - Purdue Consumer Horticulture

Blueberry damage could be plum curculio, Reduced production of strawberries

Close up of damaged young blueberry fruit

Damaged young blueberry fruit
Photo credit: R.H., Jeffersonville, Ind.

Q.  I have a few blueberry bushes planted in the backyard, and they’ve done well until last year. They started getting brown spots almost like a bite (see attached photo). No evidence of a pest and sprayed them with Sevin just in case. But that did not stop the browning, and most of the late season berries could not be eaten. Unfortunately, they appear to be starting that again this year already. Please advise and thank you! – R.H., Jeffersonville, Ind.

A.  While I can’t confirm from the photo, I suspect this might be the work of the plum curculio, a weevil-type insect pest of many fruit crops including apple, pear, stone fruit and blueberry. Female adults cut a crescent-shaped hole in the young fruit to deposit eggs just beneath the skin. The eggs hatch in a few days, and the larvae burrow and feed inside the fruit and then exit the fruit through a clean hole. The affected berries often fall off the plant. Timing of insecticide application for fruit-damaging insects is a challenge. You don’t want to apply insecticide while the plants are in bloom (to avoid killing pollinators), but by the time you notice the scars on the side of the young berry, it is too late. Good sanitation around the plants is essential to reduce future problems, since the adults overwinter under plant debris. There are several insect pests of blueberries. To confirm diagnosis, submit samples to the Purdue Plant and Pest Diagnostic Lab.

Q.  For years my wife has successfully raised strawberries, but in 2016 and 2017 they have produced very poorly. In both of those years we used barley straw instead of wheat straw for cover and alongside the row. Does barley straw reduce the vigor and yield of the strawberries? – R.B., Greensburg, Ind.

A.  I don’t think barley straw would cause a reduction in strawberry productivity. In fact, many growers prefer barley straw’s softer texture. Barley straw may have the ability to inhibit weed seedling emergence, but is unlikely to affect strawberry runner formation or fruit production.

If your strawberry planting is several years old, you might consider replacing it to avoid buildup of root pathogens. Black root rot complex is very common in Indiana. It is caused by two or more fungi and associated nematodes. Any planting more than 3 years old is likely to be suffering from black root rot complex. Do not replant onto the same spot, but move to a new area that has not had strawberries recently, and start with disease-free nursery stock.

Annual renovation of the patch is important. Start by mowing off the plants and then narrowing the rows to allow new runners to form. Fruit production will be higher on the younger runners than on old, overgrown crowns. It’s a bit too late to renovate this year, so you’ll have to wait until after your last harvest next year. You didn’t mention fertilizer application, which is another factor to consider for improved production.

See the following for more information on renovating the strawberry patch:


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