Blueberry pests

Asked July 19, 2018, 7:06 PM EDT

What is laying eggs in my blueberries??? This is our 20th year with these plants and this is the first year we have a problem. It started out with small whitish to pinkish worms floating up from my rinse water..not a lot ,but odd. They are about a half a centimeter or smaller. This made me thoroughly check more berries and I discovered some that appeared to have many small brown "eggs". The concerning thing is not knowing if or how many eggs/ larvae we popped in our mouths without knowing.. also, many suspect berries end up fine inside and the a perfect looking one is filled with eggs.. could the worms be one problem, and the eggs another? Do spiders lay eggs in blueberries?

Clackamas County Oregon

1 Response

Thank you for using Ask an Expert for help with the insect infestation on blueberries.

I suspect that the insect attacking your blueberries is the Spotted Wing Drosophila (SWD)—which may be thought of as a particularly nasty fruit fly. Instead of waiting until fruit is rotting, this insect goes after ripe fruit. The adult lays eggs in the blueberries, which then hatch out to the tiny larvae.

At this point, there is little you can do to prevent the problem—as you know. However, here are some suggestions on how to proceed:

  • Pick fruit just as or just before it is fully ripe to prevent egg-laying opportunities.
  • Avoid leaving overripe or damaged fruit on plant and quickly remove any fruit fallen to the ground.
  • Chilling fruit immediately after harvest can slow or even kill the eggs and young larvae. It may not seem pleasant but, according to research at Iowa State University, there is no known risk to human health posed by ingesting SWD.
  • If harvest is just beginning for you, cover fruiting clusters or entire fruiting plants (less than 1 mm in size if feasible) to reduce egg-laying.

For next season, there are monitoring traps to signal the beginning of the insect’s attack and the time to begin spraying. There are a number of organic spray that are quite effective on this pest. Spinosad, a bacterial product, generally provides 90% to 100% control and 5 to 7 days of residual action.

The publication Protecting Garden Fruits from Spotted Wing Drosophila shows how to construct the trap, the history of the insect, life cycle information, and control options. Some suggestions may be more suited to a larger-than-backyard planting, but can be adapted to your situation.

Good luck,