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Title: Protandry of western corn rootworm (Coleoptera: Chrysomelidae) beetle emergence partially due to earlier egg hatch of males

item LUDWICK, DALTON - University Of Missouri
item Zukoff, Anthony
item Higdon, Matthew
item Hibbard, Bruce

Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2017
Publication Date: 3/15/2018
Citation: Ludwick, D.C., Zukoff, A.L., Higdon, M.L., Hibbard, B.E. 2018. Protandry of western corn rootworm (Coleoptera: Chrysomelidae) beetle emergence partially due to earlier egg hatch of males. Journal of Kansas Entomological Society. 90(2):94-99.

Interpretive Summary: The western corn rootworm is the most economically damaging pest of corn in the United States, yet many aspects of its basic biology remain understudied. Male western corn rootworms compete for females to mate with. One tactic that males use is to emerge earlier than females so that they are ready to mate when females emerge. Since the males contribute approximately ¼ their biomass to females during mating, being ready to mate when females emerge provides an advantage to early emerging males. The relative contribution of pre-hatch and post-hatch conditions contributing to the early emergence of males was previously poorly understood. Seven populations of western corn rootworm were collected and sent to the USDA-ARS in Columbia, MO. Eggs from these populations were placed in conditions similar to their natural environment. During the Spring following the collection of each population, up to 100 newly hatched larvae were collected each day of hatch and placed on corn seedlings in rearing containers. The resulting adults were collected and their sex determined. Results indicate that both pre-hatch and post-hatch mechanisms contribute to the early development of males. This information is critical for the development of models of corn rootworm management strategies for effective control of this important economic pest.

Technical Abstract: The western corn rootworm, Diabrotica virgifera virgifera LeConte, exhibits protandry. The contribution of pre-hatch development to protandry in western corn rootworm was previously investigated with a small set of data from one population. To verify the contribution of pre-hatch development to protandry, more than 10,000 larvae from seven wild-type populations collected from across the Corn Belt were evaluated. Larvae were placed into containers on each day of hatch for each population and allowed to develop into adults. Duration of hatch for these populations ranged from 7 to 19 days with the percent of insects surviving to adulthood varying between 13 and 52 percent. The percentage of adults emerging as males on the first day was 66.92. Pre-hatch development does contribute to protandry, but overall the contribution is relatively minor compared to post-hatch development.