The Colorado Potato Beetle (Leptinotarsa decemlineata) is one of the most destructive crop pests known to mankind.

Native to the semi-arid Great Plains and Rocky Mountains of western North America, the beetle's natural host was the Buffalo Burr, a scrubby nightshade with prickly fruit. In the mid-19th century, the beetle acclimated itself to feed upon the more succulent potato plant, grown by white settlers and then commercial growers. By the beginning of the 20th century, the beetle had spread eastward and become a major pest across the continent. Efforts to keep the beetle out of Europe were successful until 1918 where the beetle gained a foothold in western France and then moved east across Europe. The beetle crossed from eastern Europe into the Soviet Union in years following World War II, where propagandists called it "The American Beetle," claiming that the United States Air Force dropped the beetles upon potato crops as a method of ecological warfare. [1]

Adults and larvae feed upon foliage. The adult is a convex, 1/3" long beetle with distinctive ten unbroken black stripes upon pale orange wing covers. Overwintering adults emerge from debris to feed and mate. These adults can fly over moderate distances to discover host plants. After mating, females will lay up to 1,000 bright orange-yellow eggs in clusters upon the underside of host plants' leaves. Larva emerge as red-orange grubs which feed heavily on foliage, molting twice within three weeks of hatching before dropping into the soil to pupate. Adults emerge in two weeks. Two generations are produced in colder northern climates and a third may be produced in warmer southern climates. Populations, if unmanaged, can quickly reach epidemic numbers and completely defoliate even the most extensive plots.

In addition to potato crops, the beetle is a known pest of other succulent nightshades including tomatoes, peppers, eggplants and tobacco. This family of plants is known to produce high levels of toxic glycoalkaloids to deter pests. The ability of the beetle to gain resistance to toxins extends also to man-made insecticidal agents:

"The first instance of Colorado potato beetle resistance to synthetic organic pesticides was noted for DDT in 1952. Resistance to Dieldrin was reported in 1958, followed by resistance to other chlorinated hydrocarbons. In subsequent years, the beetle has developed resistance to numerous organophosphates and carbamates. In some cases, a new insecticide failed after one year—or even during the first year—of use. Presently, resistance has been reported to nearly every chemical that has ever been used to control Colorado potato beetle. Obviously, not every single population is resistant to all insecticides. However, both cross-resistance and multiple resistance are rather common." [2]

The beetle has many native predators and parasites including beetles in the Carabidae family, soldier bugs (Podisus maculiventris), the parasitic wasp Edovum puttleri and nematodes Steinernema carpocapsae and Heterorhabditis heliothidis which prey upon soil-dwelling pupas. An insecticidal fungus Beauveria bassiana has been known to respond explosively in the presence of epidemic populations of these beetles, and insecticides have been developed employing this fungi in China and Russia.

Where practical, such as in the garden, manual control of the beetle is easy. Grubs are slow moving and adults tend to roll off foliage when disturbed and ineffectively attempt to hide in the soil. Adults, larvae and egg masses should be hand picked and dispatched in soapy water. Early detection and vigilance is key to management due as population growth can be explosive if neglected.

Wide scale manual control of the beetle was practiced in eastern Europe when the pest became epidemic in the 1950's. Employing the aforementioned anti-U.S. propaganda, local officials organized farmers, schoolchildren, and sometimes entire communities to hand pick the beetles when commercial pesticides were unavailable.

Cranshaw, Whitney. "Garden Insects of North America."
Ellis, Barbara W. Bradley, Marshall. et al. "The Organic Gardener's Handbook of Natural Insect and Disease Control."

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