SEASONAL AND HOST PLANT EFFECTS ON PARASITISM OF COLORADO POTATO BEETLE BY MYIOPHARUS DORYPHORAE (RILEY) (DIPTERA: TACHINIDAE)

Parasitism of Colorado potato beetle, Leptirwtarsa decemlineata (Say), by the tachinid fly Myiopharus doryphorae (Riley) was monitored over four summers. Beetle larvae were collected from potato and a wild host species, Solanum sarrachoides Sendt., and allowed to complete development in the laboratory. Parasitism rates were high, averaging 67, 58, and 45% over the 4 years, in June, July, and August, respectively. Categorical analyses indicated that parasitism rates were dependent upon year, month, and host plant species of the beetle. During 1983–1985, rates were highest in June, and decreased over the summer; results for 1986 were somewhat atypical, with parasitism rates being low in June and increasing somewhat in August. Host plant effects on parasitism varied with year. During 1983–1984, rates were higher for beetles collected from potato than beetles collected from S. sarrachoides; this tendency was reversed in 1985.