Anyone who has ever been around potato plants will recognize a yellow- and black-striped insect known as the Colorado potato beetle. Some entomologists suggest this might be the best-known beetle in North America. Sometimes called a potato bug, this beetle has been the bane of potato farmers and gardeners for more than 100 years. Potato beetles and their offspring eat the leaves of potato plants, which can be a problem for farmers and gardeners.
This insect was named the Colorado potato beetle because it was first identified in Colorado, eats potatoes, and is a beetle. North American Entomologist Thomas Say discovered the insect. Say collected the beetle when he was the zoologist on Major Stephen H. Long's 1819-1820 scientific expedition to the Rocky Mountains. Say described the insect in an 1824 report published about the Long expedition.
When Thomas Say discovered the Colorado potato beetle, the insect was feeding on a weed called the buffalo burr. Then, some 30 years later, the early settlers of Colorado introduced potato plants to the area. This Colorado beetle began using the potato as a food plant. With a new food plant available, these insects began to spread eastward. The area where the beetles were found grew by about 85 miles each year. As they moved, the beetles destroyed most of the potato plants in their path. By 1874, the Colorado potato beetle had reached the Atlantic Ocean.
Anyone who raises potatoes today is still just as likely to encounter infestations of Colorado potato beetles as were folks a century ago. And for many gardeners, the approach to control is the same as it was in those bygone times – hand picking!
Most people aren’t enthralled with the idea of picking potato beetles or their soft-bodied young off the plants. Such a task was generally assigned to youngsters in the family, and many remember the job was not a pleasurable experience.
The beetles spend the winter as adults buried in the soil. In the spring, the adults emerge and begin to lay eggs on the potato plants. The orange-yellow eggs are attached in batches to the underside of the leaves of the plants. The eggs hatch into slug-like young, which are red-colored with two rows of black spots along each side.
Picking potato bugs might be an ecologically friendly method for controlling this insect, but it is difficult to achieve good control with this approach. Consequently, potato growers quickly turned to using insecticides to deal with this pest. An inorganic compound called Paris green was used in 1865. Paris green was so-named because of its green color and its use to kill rats in the Paris subways.
Lead arsenate was also used as an insecticide against this beetle. Following World War II, DDT became the insecticide of choice to control many insects, including the Colorado potato beetle. Paris green, lead arsenate, DDT and other chlorinated-hydrocarbon insecticides were often used as a dust formulation. The insecticide was applied by shaking it through a coarse mesh bag such as one made of burlap. Needless to say, this was probably not the safest way to apply insecticides; this practice was before Environmental Protection Agency and pesticide safety rules for farm workers.
Because of the severity of the Colorado potato beetle as a pest, the insect played a role in the development of the modern pesticide industry. Hundreds of insecticides have been tested to evaluate effectiveness for beetle control. Almost all classes of insecticides have been used against the beetle over the years.
The Colorado potato beetle has responded to the widespread use of insecticides to kill it by developing resistance to many of the chemicals. Resistance means that a specific product no longer kills the insect because of genetic selection. The beetle became resistant to DDT in 1952, some 10 years after the chemical was first used for control. Today, the Colorado potato beetle is resistant to more than 50 different compounds from all classes of insecticides.
Because Colorado potato beetles are difficult to kill with most insecticides, I have decided to use an old-fashioned method of control in my garden. I resort to hand picking the insects off potato plants. Besides, I get a little bit of sadistic pleasure from killing an insect that has the audacity to make a meal of the plants in my garden.