The Colorado Potato Beetle is back!!
The Colorado Potato Beetle is oval in shape and 3/8 inch long and has a yellow-orange prothorax and yellowish white wing covers with 10 narrow black stripes. They are fairly easy to identify without a hand lens on potato leaves. Also check the undersides of the potato leaves as females will lay multiple clusters of bright yellowish-orange oval eggs. Colorado potato beetles feed primarily on potatoes. They can also attack other plants in the night shade family (Solanaceae), including: Eggplant, Tomato, and Pepper.
Colorado potato beetle adults spend the winter 5-10 inches underground in potato fields, field margins, windbreaks and gardens. Adults feed for a short time in the spring, and then begin to mate and lay clusters of 10-30 eggs on the undersides of leaves. Each female can lay up to 350 eggs during her adult life which can last several weeks. Eggs begin to hatch within 2 weeks, depending upon temperatures. Larvae cluster near the egg mass when young but begin to move throughout the plant as they eat the leaves. Larvae can complete development within 10 days if average temperatures are in the mid 80s F while it can take over a month if temperatures average near 60 F. The fourth instar larvae drop from the plant, burrow into the soil and transform into pupae.
The last or the 4th larval instar stage are responsible for as much as 75 percent of feeding damage. Potatoes can usually tolerate up to 30 percent defoliation when they are in the vegetative stage. They are much more sensitive when tubers are beginning to bulk and can only tolerate about 10 percent defoliation. Tuber bulking begins soon after flowering, making this time critical for beetle management.
Treatment of Colorado potato beetles in home gardens can be challenging. Use a combination of different pest management tactics to reduce Colorado potato beetle numbers. Keep your garden clean to avoid possible other food sources for the Colorado Potato Beetle.
Pick beetles off plants. Handpicking in small gardens can be effective. Drop adults and larvae in a pail filled with soapy water. Remove or crush the yellowish orange eggs on the underside of leaves. Also keep checking for new infestations of Colorado Potato Beetle as new adult beetles can fly into gardens.
Colorado potato beetles are resistant to essentially all synthetic pesticides like carbaryl, cypermethrin, deltamethrin, lambda cyhalothrin, imidacloprid, permethrin, and pyrethrins. These products are unlikely to be effective and their use is not suggested. Anytime you use a pesticide and it does not seem to kill Colorado potato beetles, switch to a different active ingredient.
Colorado potato beetles are not resistant to azadirachtin or spinosad. These products are also “soft” on natural enemies. Azadirachtin (Neem) – is derived from the Neem tree of Asia and Africa. It is effective for a couple of days and repeat applications are probably necessary. Azadirachtin provides poorer management of large larvae and adults. Spinosad – is made from the soil bacterium, Saccharopolyspora spinosa. It is effective for about 10 – 14 days.