Controlling roly-polys is not easy task

I have a situation in my garden that I’m sure is common to many other gardeners. At the end of the growing season and the beginning of the next season, I add grass clippings and leaves in the garden and till the organic material in. I’ve especially noticed this year that the roly-polys are so abundant and consume large quantities of leaf materials (even including radishes). I am guessing I have this problem because of the decaying organic material I continuously add to the garden. What kind of chemical should I use to control excessive insects and when should it be applied? Should I reduce the amount of organics added to the soil?

— John

You’re right about roly-polys being attracted to decaying organic matter. That is their primary food source. Roly-polys are actually crustaceans — distant relatives of crabs and lobsters. Believe it or not, they breathe through gills that are along their underside. Because of this, they really need to be in moist areas. They’re not aquatic, but desiccation is the most common reason for them dying.

Because decaying organic matter is their main food source, they’re actually beneficial in most cases. They’re an important part of the natural cycle of “recycling” organic matter back into the soil. However, they can sometimes cause problems in the garden by chewing on desirable plants. Roly-polys have pretty weak mouthparts so they’re not really a problem on older, more established plants. It’s mainly young and tender growth like seedlings, flowers and young plants that are at risk.

Controlling these little guys can be a bit of a challenge. Since they’re not closely related to insects, many insecticides don’t work well on them. The best insecticides to use are the synthetic pyrethroids like permethrin and cyfluthrin. Cyfluthrin isn’t registered for use in a vegetable garden (use that around ornamental plants) but you can use permethrin. An organic alternative is to dust the area with diatomaceous earth. It works fairly well on them, but it needs to be reapplied if it gets wet.

Speaking of wet, a good control measure is to try to dry the area out a bit. They really do prefer moist areas, and running things a bit drier may not completely eliminate them, but it often cuts their numbers to where they’re not a problem.

I guess I’m reluctant to tell you to quit adding organic matter. That’s such a good thing to do to improve our pathetic soils.

However, too much of a good thing can sometimes lead to trouble. In the future, apply no more than a 1-inch deep layer of organic matter and be sure to mix it into the soil well. That should continue to give you the benefits of improving the soil without providing too happy a place for these little guys.


I have suddenly seen a number of box elder bugs on the side of my house. One flew into my hair! I have an Austrian pine, two dying (literally, not much left on either one) silver maples and a London plane sycamore in my yard, but I haven’t seen them on any of these. Any idea where they’re coming from and should I do anything about them?

— Jennifer


Box elder bugs are a sign of autumn to a lot of folks. Box elder bugs are fairly large (half-inch long) torpedo-shaped insects. They’re black with bright red markings on their backs. These guys don’t hurt the plants in your yard, they feed on the developing seeds of the plant (usually a box elder or goldenrain tree and sometimes a maple). The problem with them is that they can become a nuisance, especially in the fall when it’s cooling down outside. They tend to congregate in large masses on the house, fences and plants in the yard and can get inside the house if there’s any kind of opening in windows, doors or screens.

Our usual way of dealing with this is to spray the tree with permethrin or bifenthrin or simply to vacuum them with a Shop-Vac. Vacuuming (and even spraying to a lesser extent) will take persistence since there’s zillions of these around and the ones you get rid of are quickly replaced by others. Other than that, spraying with an insecticidal soap may help. It probably won’t kill that many (soaps don’t work well on harder-shelled insects), but it can be irritating and might drive them away.

Dennis Hill is the nursery manager at Bookcliff Gardens, Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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