Papers submitted via IWGO Conference, Freiburg, Germany, October 2011.
Biased sex ratios, mating frequency and Nosema prevalence in European corn borer, at low population densities
Article first published online: 10 JUN 2012
© 2012 Blackwell Verlag GmbH
Journal of Applied Entomology
Special Issue: PROCEEDINGS OF THE 24th CONFERENCE OF THE INTERNATIONAL WORKING GROUP ON OSTRINA AND OTHER MAIZE PESTS (IWGO – IOBC GLOBAL)
Volume 138, Issue 3, pages 195–201, April 2014
How to Cite
White, J. A., Burkness, E. C. and Hutchison, W. D. (2014), Biased sex ratios, mating frequency and Nosema prevalence in European corn borer, at low population densities. Journal of Applied Entomology, 138: 195–201. doi: 10.1111/j.1439-0418.2012.01738.x
- Issue published online: 17 MAR 2014
- Article first published online: 10 JUN 2012
- Received: February 14, 2012; accepted: May 8, 2012.
- Areawide suppression;
- density dependence;
- Nosema pyrausta ;
- Ostrinia nubilalis ;
- reproductive manipulation
The widespread adoption of transgenic Bt maize in the Midwestern United States has led to historically low populations of the European corn borer, Ostrinia nubilalis (Hübner). Reduced population densities might influence mating and/or disease dynamics in O. nubilalis, potentially amplifying or diminishing the benefits of areawide suppression. We hypothesized that O. nubilalis mating success and infection by the microsporidium Nosema pyrausta Paillot would be decreased in areas of low pest density. Over 2 years (2009, 2010), we collected moths from black-light traps, evaluating sex ratio, mating status and infection by Nosema. We found several locations that exhibited female-biased sex ratios: to our knowledge, this is the first report of female-biased sex ratios in O. nubilalis in the Midwestern United States. Despite this bias and subsequent rareness of males, proportion mating was still high (>90%) in most locations, and there were no statistically significant relationships among population density (as measured by black-light trap catch), sex ratio and proportion of female moths that were mated. Nosema prevalence was highly variable among locations, ranging from 0% to 87% of female moths infected. Nosema infection was not significantly related to population density in either year, but was positively associated with sex ratio in 2009. It is possible that Nosema or some other microbe may be manipulating reproduction in O. nubilalis. Regardless of mechanism, our results indicate that Nosema is being maintained in O. nubilalis, which is an encouraging indication that this important natural enemy may continue to provide biological control to complement transgenic technology. Additional surveys are warranted to better understand the extent of female-biased sex ratios in low-density populations of O. nubilalis. Population models developed for studying the risk of Bt resistance in this pest should consider the possible impact of female-biased sex ratios (vs. the conventional 1 : 1 sex ratio).