Control Potato Bugs Naturally

by Thomas N. Tomas

Yesterday evening, I got home about 8:30 after being gone for two days. I went out to the potato patch to pick potato bugs. I usually go out for about five minutes in the morning and again in the evening to pick them. After being gone for two days I had a larger than normal harvest; 57 adult beetles and 2 larvae about the size of peas. This morning I got only 9 adults, no larvae. The ratio of adults to larvae at this time of year is interesting.

Ever since April, when the potato plants began to emerge, adult potato beetles have been landing on the potato leaves, mating, and laying eggs. I suspect most of the adults fly over from the neighborís pasture where buffalo burr plants abound. The native buffalo burr was (and still is) the usual food of the Colorado potato beetle before settlers introduced the potato to Western Nebraska and Eastern Colorado in the 1850ís. Both the buffalo burr and the Colorado potato beetle are native to the Eastern slope of the Rocky Mountains from Canada to Mexico. The beetle will feed on other native plants in the Solanaceae family as well as cultivated plants such as potato, eggplant, and tomato.

Colorado potato beetles were first reported on potatoes in Nebraska in 1859. They moved east at a rate of about 85 miles a year and reached the East coast in 1874, devastating potatoes all along the way. It was easy to control the beetles after chemical pesticides were discovered, but pesticide resistant strains evolved over time. By the 1980s, the Colorado potato beetles on Long Island, NY, were resistant to all but one or two of the most toxic chemicals.

It is interesting to note that the beetles in Western Nebraska and Colorado developed resistance to pesticides more slowly than those on the East coast, and they can still be controlled with many less toxic pesticides. This may be because the beetles that develop on buffalo burr plants that are not sprayed do not develop resistance. If they mate with resistant beetles, the genes for resistance are diluted in the population instead of concentrated and the population as a whole does not develop resistance as quickly.

We may be lucky in western Nebraska to have the buffalo burr and other plants and insects that evolved along with the potato beetle. Early in the season, I have noticed that the beetle eggs hatch and the larvae soon munch on the potato leaves. I crush the egg masses that I find and pick off the larvae, but they reproduce too fast for me to keep up with them. As the season progresses, I find lady bugs eating the eggs. At this time of year, I see wasps foraging in the potato patch. Last week I saw a paper-making wasp carrying off a larvae the size of a pea. I no longer worry about the egg masses, and the larvae are very scarce. Toads and at least one garter snake also work the patch. The garter snake moves too fast and the toads work the night shift, however, so I canít swear that they eat the beetles.

If you donít have buffalo burrs already, I do not recommend that you plant any. I do recommend that you plant dill, parsley, caraway or parsnips. These plants will flower and provide nectar and pollen for native wasps and ladybugs. Dill flowers the first year; parsley, caraway and parsnips flower the second year when grown from seed. When in bloom, my plants are visited by as many as 7 species of wasps, 3 species of ladybugs, numerous hover flies, and other insects that I canít identify. I also put out pans of water in the shade for the snake and toads. By feeding and watering my wild livestock, I can be sure they are in shape to work on the pests.

By hand picking and providing habitat for beneficial critters, I have the potato bug problem under control. Now, if I could only figure out how to co-exist with the grasshoppers! Why donít you share your non-chemical strategies for grasshopper control with the rest of us in NSAS? Send your ideas to Cris Carusi or the NSAS office. I look forward to reading your ideas.

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