none. Infection rates of Z. phytonomi (Arthur) Batko in alfalfa weevil, H. postica (Gyllenhal), larvae were monitored from 1979 through 1981 in Rockbridge County, Va. Infection rates of the pathogen were highest near the end of the spring alfalfa crop when alfalfa weevil larval populations were declining. Z. phytonomi was effective in suppressing alfalfa weevil populations below economic threshold levels only during a period of higher rainfall that occurred in 1979. A negative correlation between infection rates of Z. phytonomi and parasitization rates of the ichneumonid parasite Bathyplectes anurus (Thomson) (Hymenoptera: Ichneumonidae) suggests a possible interference between these two natural control agents.