Optimizing egg recovery from wild northern corn rootworm beetles (coleoptera: chrysomelidae)

Authors: Pereira, Adriano; LUDWICK, DALTON - Virginia Tech; Barry, Julie; MEINKE, LANCE - University Of Nebraska; MOELLENBECK, DANIEL - Dm Crop Research Group, Inc; ELLERSIECK, MARK - University Of Missouri; REINDERS, JORDAN - University Of Nebraska; Geisert, Ryan; HYTE, KEIRAN - University Of Missouri; ERNWALL, AMANDA - University Of Missouri; PADDOCK, KYLE - University Of Missouri; Hibbard, Bruce

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2019
Publication Date: 12/10/2019
Citation: Pereira, A.E., Ludwick, D.C., Barry, J.M., Meinke, L.J., Moellenbeck, D.J., Ellersieck, M.R., Reinders, J.D., Geisert, R.W., Hyte, K., Ernwall, A., Paddock, K.J., Hibbard, B.E. 2019. Optimizing egg recovery from wild northern corn rootworm beetles (coleoptera: chrysomelidae). Journal of Economic Entomology. 112(6):2737-2743. https://doi.org/10.1093/jee/toz234.
DOI: https://doi.org/10.1093/jee/toz234

Interpretive Summary: The northern corn rootworm is one of the most important corn pests in the U.S. Corn Belt. The larvae of this pest cause significant damage to the plants that can lead to significant yield loss. This pest is difficult to rear in laboratory conditions due to low egg production in cages. The recent resistance evolution of northern corn rootworm to transgenic corn hybrids expressing toxins highlighted the need to monitor other areas for new cases of resistance in order to preserve and prolong the life of the technology in the field. The objective of this study was to identify and compare ways to obtain enough number of eggs to perform experiments and monitor field populations for resistance to the transgenic corn. We found that northern corn rootworm females lay more eggs when kept in small numbers (1 to 10 females per) in small cages. A single female per cage was found to lay ~100 fold more eggs when compared to larger cages with >25 females. This method can facilitate to obtain numbers of eggs that can enable us to perform experiments and monitor northern corn rootworm for resistance evolution.

Technical Abstract: The northern corn rootworm, Diabrotica barberi Smith & Lawrence (Coleoptera: Chrysomelidae), is one of the most important insect pests in the U.S. Corn Belt. Efforts to obtain eggs from wild northern corn rootworm populations using techniques developed for other rootworm species have been unsuccessful due to lack of oviposition. In 2016, we evaluated four oviposition media in choice tests within each of three female densities in 30.5 × 30.5 × 30.5 cm BugDorm cages. The number of eggs laid per female was significantly affected by female density and the interaction of female density × oviposition media, but oviposition was relatively poor in all oviposition media (1.2 eggs per female when averaging the three female densities and all oviposition media). Single females were also evaluated in nonchoice assays in 6 cm × 6 cm × 8 cm clear plastic boxes and averaged up to 108 eggs per female depending on the oviposition media. In 2017, the cumulative number of eggs laid per female in boxes with one female was not significantly different from the number of eggs laid per female in boxes with 3 females. In 2018, the cumulative number of eggs laid per female was not significantly different between female densities of 1, 3, 5, or 10 females per box. Total egg production per box therefore increased as female density increased. More than 27,000 wild northern corn rootworm eggs were collected from just 190 females when collected relatively early in the field season. We now have an efficient and robust system for obtaining eggs from wild northern corn rootworm females.