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Title: EFFECT OF CRY3BB1 EXPRESSING TRANSGENIC CORN ON PLANT-TO-PLANT MOVEMENT BY WESTERN CORN ROOTWORM LARVAE (COLEOPTERA: CHRYSOMELIDAE)

Author
item Hibbard, Bruce
item VAUGHN, TY - MONSANTO CORP
item OYEDIRAN, ISAAC - UNIV OF MISSOURI
item CLARK, THOMAS - UNIV OF MISSOURI

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2005
Publication Date: 1/15/2005
Citation: Hibbard, B.E., Vaughn, T.T., Oyediran, I.O., Clark, T.L. 2005. Effect of Cry3Bb1 expressing transgenic corn on plant-to-plant movement by western corn rootworm larvae (Coleoptera: chrysomelidae). Journal of Economic Entomology. 98:1126-1138.

Interpretive Summary: The registration of transgenic corn with corn rootworm resistance offers a viable alternative to insecticides for managing the most economically important pests of corn. Maintaining susceptibility to transgenic crops (resistance management) is in the interest of growers, the Environmental Protection Agency, and industry, but this requires an understanding of corn rootworm biology and its interaction with these products that does not currently exist. Dispersal of larvae of the western corn rootworm, in specific combinations of the newly registered transgenic corn strains targeted toward corn rootworm and non-transgenic isolines was evaluated in a 2-yr field study. Each year, plant damage and larval recovery were evaluated among four treatments (straight transgenic, straight isoline, isoline with a transgenic central, infested plant, and transgenic with an isoline central, infested plant). The number of western corn rootworm larvae moving to transgenic plants from adjacent, infested isoline plants was low and not statistically significant in either 2001 or 2002. In 2001, significantly fewer larvae were recovered from transgenic plants as compared to isoline plants when both were adjacent to infested, isoline plants. In 2002, significantly more larvae were recovered from isoline plants adjacent to infested, transgenic plants than from isoline plants adjacent to infested, isoline plants. Together, these data imply that western corn rootworm larvae prefer isoline roots to transgenic roots when a choice is available. Our data also suggest that fewer adults will be produced by transgenic plants than would be the case if these plants were a preferred feeding site. 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: Dispersal of larvae of the western corn rootworm, Diabrotica virgifera LeConte, in specific combinations of transgenic corn expressing the Cry3Bb1 protein (Cry3Bb1 corn) and non-transgenic isoline corn, was evaluated in a 2-yr field study. Each year, plant damage and larval recovery were evaluated among four treatments (straight transgenic, straight isoline, isoline with a transgenic central, infested plant, and transgenic with an isoline central, infested plant), six sample dates between egg hatch and pupation, and six plants were sampled on each date, treatment, and replication. There were four replications in 2001 and five in 2002. A total of 1,500 viable western corn rootworm eggs were infested in each subplot, half on either side of each infested plant (between rows). For each subplot, the infested plant, three successive plants down the row (P1, P2, and P3), the closest plant in the adjacent row of the plot, and control plant at least 1.5 m from any infested plant, but also within the plot, were sampled. The number of western corn rootworm larvae moving to Cry3Bb1 plants from adjacent, infested isoline plants was low and not statistically significant in either 2001 or 2002. In 2001, significantly fewer larvae were recovered from Cry3Bb1 than isoline plants when both were adjacent to infested, isoline plants. In 2002, significantly more neonate western corn rootworm larvae were recovered from isoline plants adjacent to infested, Cry3Bb1 plants than isoline plants adjacent to infested, isoline plants on the second sample date. Together, these data imply that both neonate and later instar western corn rootworm larvae prefer isoline roots to Cry3Bb1 roots when a choice is possible. However, when damage to the infested, isoline plant was high, western corn rootworm larvae apparently moved to neighboring Cry3Bb1 plants and caused significant damage on the last sample date in 2001. Implications of these data toward resistance management plans are discussed.