Timing of disease-influenced processes in the life cycle of Ostrinia nubilalis infected with Nosema pyrausta

The timing of events in the life cycle of the European corn borer, Ostrinia nubilalis, can be important in the transmission and spread of the chronic disease caused by the microsporidium Nosema pyrausta. We performed two experiments with transovarially infected larvae to investigate the dynamics of the disease. In the first study, mean developmental times of infected and uninfected insects reared at 30°C were not significantly different; however, the disease significantly slowed the development of second- to fifth-instar larvae and pupae reared at 24°C. In the second study, the production of spores in the excrement of larvae increased exponentially from hatch to pupation.