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Aphthona flava
(Coleoptera: Chrysomelidae)

by Rich Hansen, USDA-APHIS-PPQ, Forestry Sciences Lab, Montana State University, Bozeman, MT 59717-0278.

Leafy spurge is an Eurasian perennial that was introduced into North America in the 19th century.

It infests several million hectares of rangelands and riparian areas in the United States and is a serious pest across the northern Great Plains where it displaces desirable grasses and forbs normally consumed by foraging cattle. Cattle and horses usually avoid leafy spurge, but should they eat it, its milky latex may cause sickness and even death. Annual direct and indirect economic losses due to leafy spurge infestation in Montana, South Dakota, North Dakota, and Wyoming are estimated to exceed $120 million. In addition, leafy spurge forms monocultures that often displace native plants and degrade wildlife habitats.

Leafy spurge has a number of biological characteristics that have caused it to be difficult to control with herbicides, and infestations generally occur in remote areas consisting of comparatively low-value land. Thus, classical biological control is envisioned as a potentially valuable spurge management tool in North America. To date, ten Eurasian insect species have been released as biocontrol agents of leafy spurge.

Aphthona flava was originally approved for release in the United States in1986. Through 1995, it has been widely released in leafy spurge infestations across the northern U.S. (19 states) and western Canada. Large populations are present in several states, including Montana and North Dakota. Aphthona flea beetles can kill leafy spurge plants as a direct or indirect consequence of larval feeding on spurge roots.

Appearance

Adult flea beetles are small (3-4 mm) and orange or orange-brown in color. A. flava adults typically hop rather than fly when disturbed. Larvae are found in the soil, on or near leafy spurge roots. They are 1-6 mm long, with short legs, yellow heads, and creamy-white bodies.

Habitat

Leafy spurge-infested grasslands.

Pests attacked

The host range of A. flava appears restricted to plants in the subgenus Esula of the genus Euphorbia. In Europe, this beetle feeds on leafy spurge and several other closely-related spurge species. There are a few native Euphorbia spp. in the U.S. that could potentially be hosts for A. flava, though no feeding has yet been documented under field conditions. A. flava will not feed on poinsettia (Euphorbia pulcherrima), and crop species and native plants outside the genus Euphorbia will not be attacked.

Life cycle

Depending on location, adults emerge from the soil beginning in June to August, and are present for several weeks to several months. A. flava adults feed on leafy spurge foliage and flowers, and high populations may defoliate spurge plants. Females lay groups of 20-30 eggs at, or just below, the soil surface, near the base of a leafy spurge stem. Newly-hatched larvae burrow into the soil and begin feeding on very small leafy spurge roots. Larvae feed on progressively larger roots and root buds as they develop. A. flava larvae overwinter, resume feeding in the spring, and then pupate in a soil cell in late spring to early summer. There is one generation per year.

Relative effectiveness

A. flava populations appear to have succesfully managed leafy spurge infestations at several locations, but the overall "success rate" is lower than that for other flea beetle species. This species seems best suited to sites that are somewhat more mesic that those utilized by A. nigriscutis or A. cyparissiae.

Pesticide susceptibility

Not known.

Conservation

For general information about conservation of natural enemies, see Conservation in the Tutorial section on this site, or the Feature Article on conservation in the Midwest Biological Control News.

Commercial availability

In some states, A. flava adults may be obtained at no cost from state weed management agencies. Several commercial suppliers can also provide A. flava adults (see the off-site publication, Suppliers of Beneficial Organisms in North America, page of the California Department of Pesticide Regulation website).

Reference

Pemberton, R.W. and Rees, N.E. (199). Host specificity and establishment of Aphthona flava Guill. (Chrysomelidae), a biological control agent for leafy spurge (Euphorbia esula) in the United States. Proc. Entomol. Soc. Wash. 92: 351-357.

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