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Title: Survival of Adult Tiphia Vernalis (Hymenoptera: Tiphiidae) after Insecticide, Fungicide, and Herbicide Exposure in Laboratory Bioassays

item Reding, Michael - Mike
item Klein, Michael

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2005
Publication Date: 4/6/2006
Citation: Oliver, J., Reding, M.E., Klein, M.G., Mannion, C., Bishop, B. 2006. Survival of Adult Tiphia Vernalis (Hymenoptera: Tiphiidae) after Insecticide, Fungicide, and Herbicide Exposure in Laboratory Bioassays. Journal of Economic Entomology. 99:288-294.

Interpretive Summary: Tiphia vernalis is a small natural enemy of Japanese beetle and oriental beetle. This insect attacks the grub stage of Japanese and oriental beetles. It was originally released into the USA during the 1920s and 1930s as a biocontrol agent for Japanese beetles. During the 1950s, 60s, and 70s when harsh insecticides were used, T. vernalis was relatively uncommon. However, during the last 20 years it has become more common. T. vernalis’ comeback is believed due to pest management programs in turf and ornamental nurseries shifting from harsh to reduced-risk pesticides. The objective of the following research was to determine whether or not some commonly used pesticides were toxic to T. vernalis. This information will enable us to make recommendations to growers about which pesticides are detrimental to T. vernalis and allow growers to time pesticide treatments so they won’t interfere with T. vernalis’ ability to attack Japanese and oriental beetles. We found that some of the older harsher insecticides were detrimental to T. vernalis, but that most of the reduced-risk pesticides could be safe for T. vernalis when applications are timed carefully.

Technical Abstract: Tiphia vernalis Rohwer is a hymenopteran ecto-parasitoid of Japanese beetle larvae. The adult wasps feed on nectar or honeydew between mid-April to 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 were determined by exposing wasps to treated foliage in the laboratory. Pesticides tested at labeled rates included the insecticides bifenthrin, carbaryl, chlorpyrifos, halofenozide, and imidacloprid; the herbicides oryzalin, pendimethalin, and a combination product with 2,4-D, dicamba, and mecoprop (MCPP) (multi-herbicide); the fungicides chlorothalonil and thiophanate-methyl. In 2000, wasps were exposed to insecticides (excluding bifenthrin) applied to maple leaves. At 24 h, only halofenozide did not reduce survival of male or female wasps relative to the control. At 48 h, male wasp mortality was no longer different among the control and insecticide treatments, but female mortality remained lower for control and halofenozide than other insecticides. During 2001 and 2002, male and female T. vernalis were exposed to all pesticides using turf cores. For both years, chlorpyrifos, imidacloprid, and bifenthrin treatments lowered adult survival relative to the control. Male mortality was higher than female for carbaryl treatments. Survival of females was not reduced by herbicide or fungicide exposure. Mortality of males was more variable; in one of two trials mortality was higher after exposure to pendimethalin and multi-herbicide than the control. Sub-lethal effects were not evaluated. Choice of pesticide may be important for conserving T. vernalis in nursery and turf settings.