Arjun Khadka, Huval, Forest, Reagan, Thomas E., Carlton, Christopher E.
Colorado potato beetle, Leptinotarsa decemlineata, is a serious pest of potatoes and other solanaceous crops. Adult Colorado potato beetles are yellowish-orange in color with ten black stripes on the wing covers (elytra), which are the modified forewings of beetles. The thorax possesses a pattern of black spots and two short lines near the middle. Adults are approximately 3/8 of an inch (10 mm) in length and oval in shape. The legs are orange in color and punctures on the surface are coarse. Larvae are plump, humpbacked in shape and pinkish-orange to orange in color, with a series of two spots per segment along each side. Eggs are yellow in color when deposited and darken to orange as they develop.
A similar species, Leptinotarsa juncta, the false potato beetle, is commonly encountered on wild host plants in Louisiana. It differs in having a reddish-brown stripe between the black stripes at the top of the elytra. Two of the black stripes along the sides of the elytra are usually partially fused. An additional species, Leptinotarsa texana, the Texas potato beetle, is also striped and similar in appearance. It has not been documented in Louisiana but occurs in Texas and Oklahoma.
Females lay eggs in clutches of 10 to 60 eggs each on the undersides of leaves. Larvae hatch in as few as four days in warm weather and up to ten days in cooler weather. Larvae undergo four growth stages (instars), requiring about three weeks to complete development in warm weather. The final larvae stage borrows into soil and pupates within a chamber of compacted soil. Adult beetles emerge from pupae in five to ten days, depending on temperature. Total life cycle is completed in about 30 days. In Louisiana, three generations can be completed annually, with adults of the third overwintering in soil or organic matter near host plants. Adults emerge and feed briefly during spring prior to mating and depositing first generation eggs.
Colorado potato beetle occurs throughout North America, including Louisiana. Its original native range is the Rocky Mountain region based on early publications. It spread across North American when potatoes became widely cultivated and has since been introduced to potato growing regions in Europe and Asia. Potatoes are the main agricultural host plant, but other crops and wild host plants in the family Solanaceae are utilized. These include eggplant, ground cherry, tobacco, tomato and buffalo bur (Solanum rostratum). Wild Solanum species such as buffalo bur are believed to be the native host plants. Damage to crops is mainly due to leaf feeding by larvae and adults. Heavy infestations can result in complete defoliation of leaves and other plant tissues.
Spread of the Colorado potato beetle throughout Europe and Asia during the mid-20th century is a well-documented example of how an invasive pest can devastate an important food crop across vast areas and impact global food supplies. During the rapid spread of the beetle into Soviet controlled eastern Europe after World War II, accusations were made that the insect had been introduced by the U.S. Central Intelligence Agency to intentionally disrupt food supplies. Almost certainly the beetle made it to these area without government assistance.
In Louisiana, the Colorado potato beetle is not considered a serious pest because potatoes are an early season crop and are typically not present during the hotter parts of the season when the beetles would normally produce large populations. False potato beetles, a native eastern U.S. species, may be common on wild hosts in Louisiana and are often misidentified as Colorado potato beetles.
In uncommon situations where the Colorado potato beetle reaches damaging populations in Louisiana, the following control strategies can be implemented.
Monitoring. Scouting fields and gardens is the first step in managing Colorado potato beetles. The host plants should be scouted at different life stages. Yellow pan traps are efficient in attracting adult Colorado potato beetles as a monitoring tool.
Cultural control. Pupation occurs beneath the soil surface, so cultural practices such as removal of debris, clean cultivation and crop rotation can significantly reduce populations. Crop rotation is an effective control practice because it prevents overwintering beetles from emerging. Simply picking the larvae and adults off of plants manually can control populations in small garden plots.
Biological control. Many generalist predators such as predatory stink bugs (Pentatomidae), ground beetles (Carabidae) and lady beetles (Coccinellidae) may keep populations in check in the absence of insecticide treatments. Also, many parasitic flies (Tachinidae) and wasps (various families) use Colorado potato beetles as hosts.
Chemical control. Insecticides such as azadirachtin (neem) and spinosad are effective in controlling larvae and adults. Strains of bacteria (Bacillus thuringiensis) can be used to control larvae. Insecticides are effective but resistance is well documented, so rotation of insecticides is critical for resistance management.
Alyokhin, A., M. Baker, D. Mota-Sanchez, G. Dively, and E. Grafius. 2008. Colorado potato beetle resistance to insecticides. American Journal of Potato Research 85: 395-413.
Brust, G. E. 1994. Natural enemies in straw-mulch reduce Colorado potato beetle populations and damage in potato. Biological Control 4: 163-169.
Grapputo, A., S. Boman, L. Lindstroem, A. Lyytinen, and J. Mappes. 2005. The voyage of an invasive species across continents: genetic diversity of North American and European Colorado potato beetle populations. Molecular Ecology 14: 4207-4219.
Hare, J. D. 1990. Ecology and management of the Colorado potato beetle. Annual Review of Entomology 35: 81-100.
Hare, J.D. 1980. Impact of defoliation by the Colorado potato beetle on potato yields. Journal of Economic Entomology 73: 369-373.
Horton, D. R., and J. L. Capinera. 1987. Seasonal and host plant effects on parasitism of Colorado potato beetle by Myiopharus doryphorae (Riley) (Diptera: Tachinidae). The Canadian Entomologist 119: 729-734.
Huseth, A. S., R. L Groves, S. A. Chapman, A. Alyokhin, T. P Kuhar, I. V. Macrae, and B. A. Nault. 2014. Managing Colorado potato beetle insecticide resistance: new tools and strategies for the next decade of pest control in potato. Journal of Integrated Pest Management 5: A1-A8.
Say, T. 1824. Descriptions of Coleopterous insects collected in the late expedition to the Rocky Mountains, performed by order of Mr. Calhoun, Secretary of War, under the command of Major Long. Journal of the Academy of Natural Sciences of Philadelphia 3(3): 403–462.
Adult Colorado potato beetle (Whitney Cranshaw, Colorado State University, Bugwood.org, Creative Commons 3.0).
Eggs of Colorado potato beetle (Whitney Cranshaw, Colorado State University, Bugwood.org, Creative Commons 3.0).
Larvae of Colorado potato beetle (Whitney Cranshaw, Colorado State University, Bugwood.org, Creative Commons 3.0).
Adult false potato beetle, commonly mistaken for Colorado potato beetle (Johnny Dell, Bugwood.org, Creative Commons 3.0).
Pupae of Colorado potato beetle (Whitney Cranshaw, Colorado State University, Bugwood.org, Creative Commons 3.0).