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Title: POST-ESTABLISHMENT MOVEMENT OF WESTERN CORN ROOTWORM LARVAE (COLEOPTERA: CHRYSOMELIDAE) IN CENTRAL MISSOURI CORN

Author
item Hibbard, Bruce
item DURAN, D - UNIV OF MISSOURI-COLUMBIA
item ELLERSIECK, M - UNIV OF MISSOURI-COLUMBIA
item Ellsbury, Michael

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2002
Publication Date: 6/1/2003
Citation: HIBBARD, B.E., DURAN, D.P., ELLERSIECK, M.R., ELLSBURY, M.M. POST-ESTABLISHMENT MOVEMENT OF WESTERN CORN ROOTWORM LARVAE (COLEOPTERA: CHRYSOMELIDAE)IN CENTRAL MISSOURI CORN. JOURNAL OF ECONOMIC ENTOMOLOGY. 2003. v. 96, # 3, p. 599-608.

Interpretive Summary: The western corn rootworm is one of the most economically important pests of corn with no viable alternative to insecticide in continuous corn. If registered, transgenic corn with resistance to this pest may offer an additional management option. Maintaining susceptibility to transgenic crops (resistance management) is in the interest of growers and industry. However, developing an effective resistance management program depends upo knowledge of some aspects of corn rootworm biology and behavior which does not currently exist. One such area is larval movement. In the current study, a central plant of an 11-plant plot was infested with 1,500 viable western corn rootworm eggs at plant emergence. After hatch, soil core samples were taken over time from the infested plant, the three plants down the row on each side of the infested plant, and the four closest plants in the two adjacent rows to sample for western corn rootworm larvae. Two combinations of row-spaciing (0.46 m and 0.91 m) and plant-spacing (0.15 m and 0.22 m) were sampled for western corn rootworm larvae along with appropriate controls in each of three or four sampling dates in 1998 and 1999, respectively. Larvae moved up to three plants away within the row or across a 0.46-m row, but not across a 0.91-m row. Plant spacing did not significantly affect the number of larvae recovered. Plants that larvae were moving away from were significantly more damaged than those plants they were moving toward. Larvae that moved accumulated significantly more biomass than larvae that did not move. 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: Little is known about many aspects of corn rootworm biology that are required for an effective resistance management program. The extent of larval movement by the western corn rootworm that occurs from plant-to-plant or row-to-row after initial establishment was evaluated in 1998 and 1999 in a Central Missouri corn field. The central plant of an 11-plant plot was infested with 1,500 viable eggs at plant emergence. After hatch, soil cores were taken over time from the infested plant, the three plants down the row on each side of the infested plant, and the four closest plants in the two adjacent rows for western corn rootworm larvae. Each combination of row (0.46 m and 0.91 m) and plant-spacing (0.15 m and 0.22 m) were sampled for western corn rootworm larvae along with appropriate controls in each of three or four sampling dates in 1998 and 1999, respectively. In 1999 only, plant damage and larval weight were also orecorded. It was documented that western corn rootworm larvae can change hosts after initial establishment and before initiating pupation. In these cases, larvae moved up to three plants away within the row or across a 0.46-m row, but not across a 0.91-m row. Plant spacing did not significantly affect the number of larvae recovered. Plants that larvae were moving away from were significantly more damaged than those plants they were moving toward. Larvae that moved accumulated significantly more biomass than larvae that did not move.