Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2008
Publication Date: 10/2/2008
Citation: Olmer, K.J., Hibbard, B.E. 2008. The Nutritive Value of Dying Maize and Setaria Faberi Roots for Western Corn Rootworm Development. Journal of Economic Entomology. 101:1547-1556. 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. The timing that dying root tissues of a grassy weed and corn no longer support growth and development of western corn rootworm larvae was evaluated under greenhouse conditions. The results demonstrate that plant tissue apparently becomes unsuitable for larval growth within the first 5 d after the dying process begins. Since partial development on an alternate host could affect 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 timing that senescing root tissues of Setaria faberi R.A.W. Herrm. and maize, Zea mays L., no longer support growth and development of neonate and 2nd instar western corn rootworm, Diabrotica virgifera virgifera LeConte, larvae was evaluated under greenhouse conditions. Three separate experiments were conducted. In the first experiment, glyphosate was used to kill S. faberi. In the second experiment, glyphosate was used to kill maize, and in the final experiment, maize was killed by severing it below the growing point. These experiments evaluated western corn rootworm larvae for survival and growth parameters among living control plants, plants severed or sprayed on the day they were infested, plants severed or sprayed 5 and 10 days before they were infested, and plants planted 5 and 10 days early and severed or sprayed 5 and 10 days before they were infested. Larvae were sampled from each of these treatments at sample times of 5, 10, and 15 d after infestation, and beetle emergence was recorded from the remaining pots. When infested on the day of glyphosate spray, significantly fewer larvae were recovered from S. faberi than from living S. faberi. Overall, when infested 5 or 10 d after being sprayed with glyphosate or being severed below the growing point, no significant larval weight gain was recorded from any treatment. Host plant tissue apparently becomes unsuitable for larval growth within the first 5 d after senescence begins.