Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2004
Publication Date: 6/1/2004
Citation: Clark, T.L., Hibbard, B.E. 2004. Comparison of non-maize hosts to support western corn rootworm (coleoptera: chrysomelidae) larval biology. Environmental Entomology. 33(3):681-689. 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 that does not currently exist. For instance, interactions of this transgenic crop with alternate hosts may be important since the recently registered product does not control larger rootworm larvae. Larval survivorship and growth parameters were monitored on the roots of 29 plant species comprised of corn, corn field grassy weeds, native prairie grasses, fence-row/forage grasses, and small grain crops. Larval recovery and growth were recorded. Larvae survived at least 6 days after infestation on 27 species and 24 days on 23 plant species. Growth and development of larvae were significantly slower on most species other than corn and adults were recovered from only five plant species in addition to corn. However, larvae survived and developed on most grasses tested and initial development on grassy corn field weeds followed by movement to transgenic corn could be a mechanism for individual larvae to overcome the transgenic protein. 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 by providing more realistic assumptions in current mathematical models.
Technical Abstract: With the recent commercialization of transgenic rootworm-resistant maize with high levels of antibiosis to larval feeding, the larval biology of western corn rootworm, Diabrotica virgifera virgifera LeConte, on hosts beyond maize has become an important topic for which limited data exist. Larval survivorship and growth parameters were monitored on the roots of 29 plant species comprised of maize, Zea mays L., maize-field weeds, native prairie grasses, fence-row/forage grasses, and small grain crops. Larval recovery and growth (measured as increases in head capsule width and accumulation of dry weight) data were recorded at five samplings (6, 10, 14, 20, and 24 d) after initial infestation of the 29 species. Recovery and growth parameters were analyzed for inter- and intraspecific differences within and between sampling dates. Larvae survived at least 6 days after infestation on 27 species and 24 days on 23 plant species. Larval recovery and growth were impacted by both species and time after infestation. Growth and development of larvae on plant species were significantly slower on most species other than maize, however, 18 of the species had larvae develop to the 2nd instar while larvae on 14 species had development to the 3rd instar. Adults were recovered from five plant species in addition to maize. Because rootworm resistant transgenic maize with high levels of antibiosis is becoming a part of the agroecosystem, grassy maize field weeds as well as adjacent forage and fencerow grass species may become more important in the western corn rootworm life cycle, particularly as genes conferring resistance to postemergent herbicides, such as glyphosate, are stacked with transgenic rootworm-resistant maize hybrids.