Colorado Potato Beetle

You may have played with (or been horrified by) potato bugs as a child. The Colorado potato beetle is not that bug. [Those bugs are Jerusalem crickets, which are neither crickets nor from Jerusalem, but we will discuss those pests another day.] 

The Colorado potato beetle looks more like a striped cucumber beetle. Unfortunately, the infamous Colorado potato beetle eats more than just potatoes. To make matters worse, this pest has an impressive ability to become resistant to even the harshest chemicals.

Colorado potato beetle (Scott Bauer, USDA ARS) Public Domain

History of the Colorado potato beetle

The Colorado potato beetle (Leptinotarsa decemlineata) is also known as the ten-lined potato beetle, ten-striped spearman, or simply the Colorado beetle. First identified in 1824, this pest is native to southwest North America. Initially, this dome-shaped beetle preferred wild members of the nightshade family, but, by 1840, the domesticated potato became its favorite food, followed closely by tomatoes, peppers, and eggplants. Exports of potatoes (and the Colorado potato beetle) to France and Germany inspired the world’s first plant quarantine laws. During the Cold War, the CIA was accused of releasing Colorado potato beetles in Russia, in an effort to threaten the Soviet Union’s food supply. In 2014, to call a pro-Russian separatist of the Ukraine a ‘koloradi’, a nickname given to the invasive Colorado potato beetle, was an insult directed at their similar orange and black stripes. In Hungary, a statue commemorates the arrival of this difficult to control pest.

Native range of the potato (green) and the Colorado potato beetle (yellow); Beetle range as of 2002 (orange). (Franz Geller-Grimm) CC BY-SA 2.5

Colorado potato beetle description

This stubby, round beetle has the same size and shape as a Japanese beetle. It is usually 1/ to 1/2 an inch long and tends to be bright yellow or orange, with five stripes on either side of its wing covers (elytra) and scattered holes (elytral punctures) on its shoulder covers (thorax). Colorado potato beetles are easily confused with their close cousins, false potato beetles. False potato beetles, L. juncta, have stripes, too, but their stripes tend to be white, with light brown center stripes, and their elytral punctures are spaced in an orderly fashion.

Adult Colorado potato beetle (Udo Schmidt) CC BY-SA 2.0

False potato beetle (Mattrupp) CC BY 2.5

Colorado potato beetle lifecycle

Adult females can lay over 500 eggs in one month. These bright yellow or orange, torpedo-shaped eggs are laid in clusters on the underside of leaves. These beetles go through four stages, or instars, on their way to adulthood. Each instar only lasts 2 or 3 days. Eggs hatch after 4 to 15 days, depending on temperature. These larvae have humped backs, are dark reddish brown, with two rows of spots on either side (if you look very closely). They can usually be found near abandoned egg cases. By the time these baby beetles reach their third instar, they are bright red with black heads. These pests will continue feeding and growing until they reach adult size. Then, during the fourth instar, they enter a nonfeeding, prepupal stage. These larvae are a lighter color and they don’t move around very much.

First instar Colorado potato beetles (Whitney Cranshaw) CC BY 3.0

Third instar beetles (Pollinator) CC BY-SA 3.0

4th instar Colorado potato beetle (Stephan Czuratis) CC BY-SA 2.5

From there, they drop to the ground and burrow into the soil, where they pupate. In only 5 to 10 days, an adult beetle emerges, and the cycle begins again. While these pests can enter diapause, a form of dormancy, during harsh weather, there can be 3 or more generations each year.

​Controlling Colorado potato beetles

Insecticides were used intensively to control this pest until, in the 1950s, it became resistant to DDT. It has developed similar resistance to other chemicals. Rather than boosting its resistance by exposing it (and us) to ever-harsher chemicals, handpicking and promoting natural predators are your best control measures. ​

Colorado potato beetle pupa (Whitney Cranshaw) CC BY 3.0

Natural predators, such as ladybugs, pink lady beetles, spiders, ground beetles, lacewings, wasps, damsel bugs, beneficial nematodes, and praying mantids all enjoy feeding on these pests, so avoid using broad spectrum pesticides.

​Neem oil and Bt sprays can be used as effective controls. Dusting with diatomaceous earth (DE) has also been shown to be effective.

Pink lady beetle feeding on potato beetle eggs (Whitney Cranshaw) CC BY 3.0