Wireworm?

Asked March 29, 2020, 11:39 PM EDT

Hi! Do you know what these small brown worms or centipedes are? And could they be the cause of plant declines in a raised bed? I have a raised bed and I think it has some sort of root eating infestation as recently all my transplants quickly lose vigor and have stunted root growth. I put out potato chunks as they say to do when testing for symphilins, and the attached photo was the result . Help please, I’d love to get this bed back into veggie crop production this year. Thanks!

Benton County Oregon

1 Response

Hi and thanks for contacting Ask an Expert.
Those are millipedes. Wire-worms are a lighter color and symphylans are tiny, the size of a ball point pen head or a tad bigger. Some symphylans are microscopic.
Millipedes have been growing in large numbers the last few years in gardens that I have seen.
The last one was a strawberry bed and they decimated the strawberries whether ripe or not. We used insecticidal soap weekly to get rid of them. You can turn over the soil and find them, bag them, seal the bag and put in the garbage along with the spraying them. I would also recommend Neem oil if you have a lot of them on the surface or in your bait potatoes.
Neem oil will kill everything so you need to be careful. And if you want to use Neem, order it online - pure Neem, no additives. You only need a teaspoon to a quart of water, it is effective, organically approved and kills the insect. This is an approved organic spray. It is also a fungicide so may help with spores in the soil.
Since this is a raised bed, I would gently sift through the soil and try to remove as many as possible by hand. We found they congregated on the wooden sides of the raised bed.
The insecticidal soap can be made from liquid soap, oil and water. Use about a tablespoon of liquid soap, tablespoon of any vegetable oil and fill the spray bottle with water. This solution must be shaken as does the Neem oil. So spray, shake and spray again.
While millipedes are supposed to eat decaying matter, they have proven to like a variety of roots and fruit in my experience.
If you have any further questions, please do not hesitate to contact us.