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item Hibbard, Bruce

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2004
Publication Date: 8/26/2004
Citation: Wilson, T.A., Hibbard, B.E. 2004. Host suitability of nonmaize agroecosystem grasses for the western corn rootworm (coleoptera: chrysomelidae). Environmental Entomology. 33:1102-1108.

Interpretive Summary: The registration of transgenic corn with resistance to corn rootworm larval feeding offers a viable alternative to insecticides for managing the most economically important insect pests of corn. Maintaining susceptibility to transgenic crops (resistance management) is in the interest of growers, the Environmental Protection Agency, and industry, but requires an understanding of corn rootworm biology (such as larval use of alternate hosts) that does not currently exist. We evaluated 22 plant species including corn, corn-field weeds, and a few other species planted in greenhouse trials as larval hosts of the western corn rootworm. Larvae survived at least 14 d on 21 species and 26 d on 18 species. Final stage larvae were recovered from 16 species and larval growth rate was not significantly different from corn on three species. Since partial development on an alternate host could effect the durability of transgenic corn, this information will be important to seed companies, the Environmental Protection Agency, and modelers in their attempts to develop resistance management plans for transgenic corn.

Technical Abstract: The biology of western corn rootworm larvae, Diabrotica virgifera virgifera LeConte, on alternate hosts has become an important topic with the recent commercialization of transgenic, rootworm-resistant maize. Larval development and survivorship were monitored on 22 plant species including maize, Zea mays L., maize-field weeds, and selected native prairie grasses, fence-row/forage grasses, and small grain crops planted in greenhouse trials. Larval recovery was monitored 7, 14, 21, and 26 d after infestation. The dry weight of larvae and adults was recorded in addition to pronotum width of adults and head capsule width of larvae. Larvae survived at least 14 d on 21 species and 26 d on 18 species. Third instars were recovered from 16 species. The head capsule width of larvae recovered from quackgrass, Elytrigia repens L., Rhodes grass, Chloris gayana Kunth, and fall panicum, Panicum dichotomiflorum Michx, were not significantly different from maize on all four sampling days. Adults were recovered from 10 species. These data along with other studies show that almost all grasses tested provide enough nutrition for larvae of the western corn rootworm to survive 14 days, and larval development to the third instar can occur on most grasses. The potential for rootworm larvae to move between weeds within or adjacent to a maize field could be an important factor in resistance management of transgenic, rootworm-resistant maize. However, the long-term implication of such movement for a low-dose transgenic event has yet to be worked out.