common name: Colorado potato beetle
scientific name: Leptinotarsa decemlineata (Say) (Insecta: Coleoptera: Chrysomelidae)

common name: false potato beetle
scientific name: Leptinotarsa juncta (Germar) (Insecta: Coleoptera: Chrysomelidae)

Introduction - History - Distribution - Description - Life Cycle - Hosts - Key to the Leptinotarsa Species of Florida - Management - Selected References

Introduction

True "potato beetles" are members of the beetle genus Leptinotarsa, with 32 species in North America, including Mexico; 12 species in the continental United States, including two species in Florida (Arnett 2000). The most notable is the Colorado potato beetle, Leptinotarsa decemlineata (Say), found in Florida and most of the United States, and introduced into Europe and parts of Asia. It is a serious pest of potatoes and other solanaceous plants.

adult

The family Chrysomelidae, or leaf beetles, is one of the seven largest families of Coleoptera. All members are phytophagous, both as larvae and as adults. Some feed on roots, others on stems or leaves of herbaceous plants, and some mine the leaves of woody plants. They belong to the subfamily Chrysomelinae represented by over 2,000 species distributed throughout the world. Most larvae of the Chrysomelinae live openly on plants while feeding, and they usually burrow into soil to pupate. Many economically important species are found in this subfamily.

History

The Colorado potato beetle was first discovered by Thomas Nuttal in 1811 and described in 1824 by Thomas Say from specimens collected in the Rocky Mountains on buffalo-bur, Solanum rostratum Ramur. The insect's association with the potato plant, Solanum tuberosum (L.), was not known until about 1859 when it began destroying potato crops about 100 miles west of Omaha, Nebraska. The insect began its rapid spread eastward, reaching the Atlantic coast by 1874.

The evolution of the name "Colorado potato beetle" is curious since the beetle did not originate in Colorado but is believed to have originated in central Mexico. It had a series of names from 1863 to 1867, including the "ten-striped spearman," "ten-lined potato beetle," "potato-bug" and "new potato bug." Colorado was not connected to the insect until Walsh (1865) stated that two of his colleagues had seen large numbers of the insect in the territory of Colorado feeding on buffalo-bur. This convinced him that it was native to Colorado. It was C.V. Riley (1867) who first used the combination: Colorado potato beetle.

Distribution

Leptinotarsa decemlineata occurs in most areas of the United States, including Florida. It was first reported in Florida in 1920, but it is not often a major pest.

Leptinotarsa juncta is found primarily in the southeastern United States from northern Florida to eastern Texas, north to Missouri, southern Illinois and Indiana, and east to Maryland and Virginia.

Description

The genus Leptinotarsa is assigned to the tribe Doryphorini containing three genera in the United States, recognized by having the procoxal cavities open behind, simple claws separate at base and usually divergent. Species of Leptinotarsa are recognized by the following features: maxillary palpi (mouthparts) with apical segment shorter than preceding, truncate; mesosternum not raised above the level of prosternum; profemur of male simple.

Two species of Leptinotarsa occur in Florida: L. decemlineata, the Colorado potato beetle, and L. juncta (Germar), the false potato beetle. The latter incorrectly has been called the "false Colorado potato beetle" because of its similarity to L. decemlineata.

Adults: The adult measure about 3/8 inch long and are yellowish-orange with multiple black stripes down the back (Wilkerson et al. 2005).

In L. decemlineata, the pale yellow elytra are outlined in black, with each elytron having five vittae (broad longitudinal stripes). Vitta 1 is shorter than other four and adjacent to the sutural margin. Vittae 2 through 5 extend more than half the length of the elytron and are very distinct. Elytron punctation is coarse in irregular rows.

Colorado potato beetle adult

In L. juncta, each pale yellow elytron has five black vittae, with vitta 1 bordering sutural margin and extending from just below the base to the apex. Vitta 2 shorter than first and not reaching base. Vitta 3 and 4 connect at the apex of elytron with space between black. Vitta 5 is along the lateral margin of elytron. Punctation is coarse, in very regular rows outlining each vitta. There is a distinct black spot on outer margin of femur.

Eggs: Eggs are bright orange in color and football-shaped.

eggs

Larvae: The small, cyphosomatic, reddish larvae of the Colorado potato beetle are 1/2 inch long when mature. The larvae have black spots down the sides.

larva

Pupae: Pupae are yellow.

pupa

Life Cycle

The life cycle of the Colorado potato beetle starts with the adult as the overwintering stage. They dig into the soil to a depth of several inches and emerge in the spring. They feed on newly sprouted host plants where they mate.

Females deposit eggs on the surface of the host plant's leaves, usually on the undersurface protected from direct sunlight. An egg mass may contain from 10 to 40 eggs, and most adult females deposit over 300 eggs during a period of four to five weeks. Eggs hatch in four to five days depending in part on temperature and humidity.

The four larval instars last a total of 21 days. The larvae feed almost continuously on the leaves of the host plant, stopping only when molting.

Larvae drop from the plants and burrow into the soil where they construct a spherical cell and transform into yellowish pupae. This lasts from five to 10 days. There are one to three generations per year, depending on latitude.

The life cycle of the false potato beetle is similar to that of the Colorado potato beetle. Eggs hatch in four to five days and the larvae feed on the leaves of the host plants. There are four larval instars lasting 21 days. The larvae drop to the soil to pupate, and pupation lasts 10 to 15 days.

Hosts

Potatoes are the preferred host for the Colorado potato beetle, but it may feed and survive on a number of other plants in the nightshade family: eggplant, tomato, pepper, tobacco, ground cherry, horse-nettle, common nightshade, belladonna, thorn apple, henbane, and its first recorded host plant: buffalo-bur.

damage

The false potato beetle is found primarily on the common noxious weed, horse-nettle, Solanum carolinense L. It also feeds on other solanaceous plants, such as species of ground cherry or husk tomato, Physalis spp., and common nightshade, Solanum dulcamara (L.).

Key to the Leptinotarsa Species of Florida

Elytral punctation in regular rows from base to apex, vitta 3 and 4 connect at apex of elytron, space between black; black spot on outer margin of the femur. (southeastern U.S.)..... juncta (Germar)

Elytral punctation irregular, not forming regular rows, no black space between vitta 3 and 4; no black spot on legs. (widespread)..... decemlineata (Say)

elytron comparisons

Management

The Colorado potato beetle may be managed culturally by crop rotation or destruction of crop debris. Insecticides are commonly used to control populations of Colorado potato beetle, but resistance to insecticides develops rapidly (Wilkerson et al. 2005).

Insect Management Guide for vegetables

Selected References

Authors: Richard L. Jacques, Jr., Florida Department of Agriculture and Consumer Services, Division of Plant Industry; and Thomas R. Fasulo, University of Florida
Originally published as DPI Entomology Circular 271. Updated for this publication
Photographs: Lyle Buss and James Castner, University of Florida; Whitney Cranshaw, Colorado State University; and USDA
Illustrations: FDACS-Division of Plant Industry
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-146
Publication Date: July 2000. Latest revision: August 2007.
Copyright 2000-2007 University of Florida

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