Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 27, 2001
Publication Date: N/A
Interpretive Summary: The European corn borer (ECB) is a serious pest of corn throughout corn growing regions of the world. Biological control is one method of managing this insect. Many organisms including predators that eat eggs and larvae, parasitoids that use eggs and larvae as hosts, and disease-causing microbes are biological control agents. A disease-causing microbe, Nosema pyrausta, ,occurs in most populations of ECB and is passed from generation to generation in the insect egg or through larval fecal materials. Scientists conducted research to better understand what environmental conditions influence the pathology of N. pyrausta. Cool temperatures, 16 deg C vs. 27 deg C, during egg laying reduced numbers of eggs by 5% for insects not infected with N. pyrausta and by 50% for insects infected with N. pyrausta. This research suggests that a cool period in nature during egg laying would greatly reduce the number of ECB. This research helps crop consultants and dresearchers in predicting natural populations of ECB.
Technical Abstract: Nosema pyrausta is an obligate pathogen causing reduced fecundity and longevity of Ostrinia nubilalis (Lepidoptera: Crambidae). This study was conducted to determine the effect of temperature and N. pyrausta infection on O. nubilalis egg production, hatch, and level of infection. In both scenarios, infected and noninfected insects were placed in two different temperature regimes. The first regime allowed moths to oviposit under optimum conditions (27 deg C, 65% RH, 16:8 (LD)), while moths in the second regime were held at 16 deg C for one week after which they were moved to optimum conditions to oviposit. Averaged over temperatures, infected females produced 25% fewer eggs than their noninfected counterparts. Cool temperatures alone reduced egg production by 16% when averaged over infected and noninfected moths. Nosema pyrausta infection reduced egg production per female by 53% and 11% in 16 deg C and 27 deg C temperature regimes, respectively. Exposure to cool temperatures alone reduced egg production by infected individuals by 50%, while noninfected individuals in cool conditions had only a 5% reduction in egg production. Exposure to cool temperatures during the ovipositional period had a more dramatic impact in reducing egg production in N. pyrausta infected than noninfected O. nubilalis.