TEMPORAL DYNAMICS OF ENTOMOPHAGA-MAIMAIGA AFTER DEATH OF GYPSY-MOTH (LEPIDOPTERA, LYMANTRIIDAE) LARVAL HOSTS

Conidial discharge by a 1984 Japanese isolate of Entomophaga maimaiga Humber, Shimazu & Soper infecting gypsy moth, Lymantria dispar (L.), larvae was investigated under field conditions. On an hourly basis, levels of conidia discharged were correlated with relative humidity (RH) for the previous 2 h and with leaf wetness for the previous 3 h. Greater than 90% of cadavers discharged maximum numbers of conidia between 2000 and 0800. Increased hours of RH greater-than-or-equal-to 70 or greater-than-or-equal-to 90% after larval death and before sporulation began resulted in increased numbers of conidia released during the first day of sporulation. One-day-old cadavers usually sporulated within an average of 1.5-2.2 d of being placed in the field and 71.6% of cadavers produced conidia for less-than-or-equal-to 2 d during the average of 5.4 d they were monitored. Cadavers of larvae infected with E. maimaiga demonstrated the ability to sporulate, cease sporulation, and later sporulate again; however, the numbers of conidia discharged after conidial discharge resumed were much lower. Of 40 larvae infected with E. maimaiga that produced only resting spores after death, 50% persisted on tree trunks for only 2 d, although 19.7% still remained attached to tree trunks after 9 d.