LEBIA GRANDIS (COLEOPTERA: CARABIDAE), A PREDATOR AND PARASITOID OF LEPTINOTARSA (COLEOPTERA: CHRYSOMELIDAE): PREY PREFERENCE AND HOST SUITABILITY.

Authors: Weber, Donald; Rowley, Daniel; Greenstone, Matthew; Athanas, Michael

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2006
Publication Date: 6/16/2006
Citation: Weber, D.C., Rowley, D.L., Greenstone, M.H., Athanas, M.M. 2006. Lebia grandis (coleoptera: carabidae), a predator and parasitoid of leptinotarsa (coleoptera: chrysomelidae): prey preference and host suitability.. Journal of Insect Science. V.6;09

Interpretive Summary: The Colorado potato beetle (CPB) is one of the most notorious pests of agriculture. A native of western North America, 150 years ago it shifted from native plants to the cultivated potato, and has been a pest of potatoes, tomatoes and eggplant ever since. Control with insecticides has been problematic, since CPB has rapidly and repeatedly developed resistance. Native natural enemies which serve as predators or parasites of CPB, and thus provide biological pest control, have not been sufficiently investigated. One of these is the carabid ground beetle Lebia grandis. This insect is unusual in being both a voracious predator of CPB eggs and larvae in its adult stage, and a parasitoid (parasite which kills its host) in its larval stage. Historical records show that, while CPB is its only recorded host, CPB was not present in much of the original range of Lebia until the late 19th century, pointing to a different original host, the false potato beetle, Leptinotarsa juncta. Using CPB, the false potato beetle and another close CPB relative, L. haldemani, we found that Lebia accepts eggs and larvae of all 3 species as adult food, and also is capable of parasitizing all 3 species in its larval phase. Our laboratory comparisons support the false potato beetle as its original host, because it is best suited to Lebia reproduction, based on successful emergence of the adult carabid parasitoid from over 40% of hosts, compared to less than 12% emergence from CPB and L. haldemani. Additional insight into Lebia's requirements for food and favorable physical environments may allow us to design agroecosystems, such as those with cover crops, which conserve and augment this potentially important natural enemy.

Technical Abstract: Lebia grandis, recorded as a parasitoid only on Colorado potato beetle, Leptinotarsa decemlineata, also is capable of parasitizing the false potato beetle (L. juncta) and another congener, L. haldemani. Historical records show that Colorado potato beetle, while the only recorded host, was not present in much of the original range of L. grandis, and may not have been its host prior to its expansion into eastern North America, where L. juncta is endemic. Our laboratory comparisons suggest that L. juncta, the presumptive original host, best supports the development of the parasitoid larval L. grandis, based on 43.6% successful emergence of the adult carabid parasitoid, compared to 11.5% from the two other Leptinotarsa. L. grandis adults accept eggs and larvae of all 3 Leptinotarsa species as adult food. Naive, newly-emerged adults show no preference when presented the 3 species of third-instar larvae, which they consume at a mean rate of 3.3 per day, a rate which does not differ significantly by sex, larval host, or weight at emergence. Such adults when presented with equal amounts by weight of the 3 species of Leptinotarsa eggs, consume the equivalent of 23.0 L. decemlineata eggs per day, with 25% higher consumption by females, and consumption of L. juncta eggs 37% higher by weight than either L. decemlineata or L. haldemani. Insight into the biotic and abiotic limitations on L. grandis should aid in determining its potential for suppression of Colorado potato beetle by biological control in diverse agroecosystems.