Survival of adult Tiphia vernalis (Hymenoptera: Tiphiidae) after insecticide, fungicide, and herbicide exposure in laboratory bioassays.

Tiphia vernalis Rohwer is a hymenopteran ectoparasitoid of Japanese beetle, Popillia japonica Newman, larvae. The adult wasps feed on nectar or honeydew between mid-April and late June. Adults may contact pesticides when landing on foliage or when females hunt for grubs in the soil. The lethal effect of nursery, turf, and landscape pesticides was determined by exposing wasps to treated foliage in the laboratory. Pesticides tested at labeled rates were the insecticides bifenthrin, carbaryl, chlorpyrifos, halofenozide, and imidacloprid; the herbicides oryzalin, pendimethalin, and a combination product with 2,4-D, dicamba, and mecoprop (multiherbicide); and the fungicides chlorothalonil and thiophanate-methyl. During 2001 and 2002, male and female T. vernalis were exposed to pesticides by using turf cores. For both years, bifenthrin, chlorpyrifos, and imidacloprid treatments lowered adult survival relative to the control, but halofenozide had minimal effect on mortality of males and females. More males than females died after exposure to carbaryl treatments. Survival of females was not reduced by exposure to herbicides or fungicides. Females were apparently more tolerant of pesticides than males. Mortality of males in response to herbicides and fungicides was more variable than for females; in 2002 trials, male mortality was higher after exposure to multiherbicide, oryzalin, pendimethalin, and thiophanate-methyl than the control. The fungicide chlorothalonil did not increase mortality of males or females in either year. Sublethal effects were not evaluated. The study indicates the choice of pesticide may be important for conserving T. vernalis in nursery, landscape, and turf settings.