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Learn to Control the Colorado Potato Beetle

Written by Stephanie on June 19th, 2013

Colorado Potato Beetles are important pests of potato plants.  Contrary to their name, they are present throughout the United States and Canada.  It is native to Mexico, where it feeds on the buffalo burr plant.  In addition to potatoes, Colorado potato beetles eat eggplants, peppers and tomatoes in addition to potatoes.

Colorado potato beetles are yellow with black stripes across the back and an orange head. The larvae are red with black spots.   The eggs are orange-yellow and are laid in batches of two dozen or so.

Adult Colorado potato beetles overwinter in the soil.  As it warms up, they emerge begin to feed on weeds and potato plants.  They are so aggressive they will even burrow in the soil to eat emerging foliage.  Females lay eggs under the leaves of the host plant.  Over the course of four or five weeks, the female can lay up to 500 eggs.

The eggs hatch after four to nine days and the larvae begin feeding on the host plant immediately.  Full grown larvae drop to the soil to pupate.  They emerge in five to ten days.  The whole cycle, from the egg being laid to the adult emerging, can take as few as 21 days.  Multiple generations of these pests are born each summer, especially in the Southern states where it warms early and the frost comes late.

While a potato plant can survive a defoliation of as much as 30% without reducing its yield, Colorado potato beetles and their larvae frequently strip the plant right down to the ground.  Control measures should be taken when an average of one beetle or larvae is found per plant.

Cultural controls. Planting fast maturing potatoes can help by harvesting before the second and subsequent generations of potato beetles are born.  Late plantings of heat tolerant potatoes after most of the overwintering adults have starved can also work.  Spreading straw as mulch around the potato plants can delay beetle development.

Biological controls. . Biological controls include several native insects.  The difficulty with biological controls is that they do not operate early enough to prevent beetles from defoliating plants or making it necessary to use chemical controls to prevent defoliation.   The blue-green ground beetle Lebia grandis often plays a significant role in controlling the beetle, as do two species of predatory stink bugs, a parasitic fly, and at least two ladybug species. A native fungus, Beauveria bassiana, often kills high numbers of beetles late in the season, leaving a characteristic white cadaver of beetle adults and larvae. Restraint in pesticide use will maximize the effectiveness of these natural biological control agents. There is also a commercially available biological control product, Bacillus thuringiensis, var. tenebrionis, that is effective in killing the Colorado potato beetle. Sold under many trade names, including Novodor, Foil, and Trident, this bacterium is most effective when used against young larvae and should be used starting when eggs begin hatching.

Chemical controls. Potato bugs are bad about developing resistance to pesticides.  Most common consumer pesticides are now ineffective against the beetles.  Neem oil and rotenone are still effective.  While rotenone is very toxic, neem oil has low toxicity and is approved for food crops.

 



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