Reoccurrence of the microsporidan Perezia pyraustae in the European corn borer, Ostrinia nubilalis, reared on diet containing fumidil B

Fumidil B suppressed the level of Perezia pyraustae infection in the larvae of the European corn borer, Ostrinia nubilalis, while they were feeding on diet containing the drug. After feeding ceased and the gut was emptied of diet containing Fumidil B, the level of infection again increased. Drug levels of 1000 and 1500 ppm in the meridic diet significantly reduced the mean level of P. pyraustae in the adult stage as compared with lower drug levels of 200 and 500 ppm. The level of infection increased throughout the pupal and adult stages, but during the pupal stage it increased much faster in the female than in the male. The rapid increase in the level of infection in the female is discussed in relation to transovariole transmission to the next generation.