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Title: ALTERNATE HOST PHENOLOGY AFFECTS SURVIVORSHIP, GROWTH AND DEVELOPMENT OF WESTERN CORN ROOTWORM (COLEOPTERA: CHRYSOMELIDAE) LARVAE

Author
item CHEGE, PETER - UNIVERSITY OF MISSOURI
item CLARK, THOMAS - UNIVERSITY OF MISSOURI
item Hibbard, Bruce

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2005
Publication Date: 11/27/2005
Citation: Chege, P., Clark, T.L., Hibbard, B.E. 2005. Alternate host phenology affects survivorship, growth and development of western corn rootworm (Coleoptera: chrysomelidae) larvae. Environmental Entomology. 34:1441-1447.

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. A study to determine the impact of alternate host plant phenology on the survivorship (percentage larval recovery), growth (dry-weight gain), and development (head capsule width) of larvae of the western corn rootworm was conducted under greenhouse conditions. Six weed species were evaluated under eight weekly infestations and three sample times with five replications. Percentage larval recovery, change in head capsule width, and weight gain were significantly impacted by infestation time and host species. Larval survivorship in grassy weeds was highest in large crabgrass, followed by giant foxtail, witchgrass, woolly cupgrass, and green foxtail. Infestation 4, 5, and 6 weeks after planting supported western corn rootworm survivorship, growth and development better than infestation in later weeks. 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 commercial release of transgenic maize with resistance to rootworms incorporated with glyphosate tolerance has become a reality, and questions have arisen regarding the impact of grassy weed phenology on the biology of the western corn rootworm biology, Diabrotica virgifera virgifera. A study to determine the impact of host plant phenology on the survivorship (percentage larval recovery), growth (dry-weight gain), and development (change in head capsule width) of western corn rootworm larvae was conducted in a split-split-plot randomized complete block design experiment under greenhouse conditions. Six host species were evaluated under eight weekly infestations of 15 neonate western corn rootworm larvae that were sampled for larval recovery after 7, 14, and 21 d, each with five replications. Percentage larval recovery, change in head capsule width, and weight gain were significantly impacted by infestation time and host species. Other than from maize, larval survivorship was highest in large crabgrass, Digitaria sanguinalis, followed by giant foxtail, Setaria faberi, witchgrass, Panicum capillare, woolly cupgrass, Eriochloa gracilis, and green foxtail. Infestation in weeks 4, 5, and 6 supported western corn rootworm survivorship, growth and development better than infestation in infestation times. Unfavorable host phenology, along with herbicide sprays, may be factors in the potential for larvae to move between grassy weeds and transgenic rootworm-resistant maize.