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Quick Update on Colorado Potato Beetles

Jeffrey Hahn, Asst. Extension Entomologist

Do you have a problem with Colorado potato beetles in your garden? If you grow potatoes, there is a good chance you see them at one time or another on your plants. Don’t forget that in addition to potatoes, they can also attack eggplants, tomatoes and peppers. This insect can be challenging to manage but here are a few tactics you can use to deal with this pest.

Monitor susceptible plants regularly so you know if Colorado potato beetles are present in your garden. If you have a history of these insects in your garden, the odds are good you will see them again. Because you can have overlapping generations, you can find all life stages in your garden at any given time. Once they are active in spring, you will generally have Colorado potato beetles in your garden all summer.

If you have a smaller garden, and the time, handpicking is a great nonchemical control method. To be sure they are killed, just toss adults and larvae into a bucket of soapy water. For the really small, young larvae, just put on your gloves and squish them. And don’t forget the eggs. Look for them on the underside of the leaves. They are easy to recognize as they are orange and in clusters.

If physical removal is not practical, you may wish to use an insecticide. There are two low impact products available. Spinosad is produced by the fermentation of a soil-dwelling bacterium, Saccharopolysora spinosa. It is quick acting, attacking the nervous system of insects. It is most effective against caterpillars, flies (mostly leafminers), and thrips, as well as leaf beetles, grasshoppers and other insects that consume a lot of foliage.

art5-2_600.jpgNeem is derived from the neem tree, a plant found in arid tropical and subtropical areas. Neem can deter insect pests in one of several ways. They can inhibit their feeding, repel them, or disrupt their life cycle preventing them from successfully molting. Neem is generally effective against a wide array of insects, including beetles.

You might be wondering about Bacillus thuringiensis var. tenebrionis, a commonly used home garden product for leaf beetles, like Colorado potato beetles. This bacterial insecticide, which acts as a stomach poison, is quite effective against young larvae. However, this product is no longer registered in Minnesota. It was previously available from Bonide in a product called Colorado Potato Beetle Beater. If you look at Bonide’s products, you will still find a product with that name, but it now contains spinosad.

There are a wide variety of residual insecticides, such as permethrin and carbaryl that are labeled to treat Colorado potato beetles. However, there is a good chance that the Colorado potato beetles in your garden are resistant to these insecticides already. This will be particularly true if you are any where near a commercial potato field. Instead try a newer insecticide, like esfenvalerate. The beetles in your garden are more likely to be susceptible to it.
