ESA Annual Meetings Online Program
Potential lethal effects of two commonly applied turf fungicides on larvae of the Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae)
Larvae of the Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae) are rarely found in golf course putting greens, despite seemingly ideal characteristics including adequate soil moisture, low-cut turf height and reduced predator abundance. We hypothesize that this phenomenon may be explained by the frequent application of fungicides to putting greens, where some fungicides may have a secondary lethal effect on larvae. In a field study, 10 adult males and 10 females were caged over individual experimental putting green plots treated with maximum-labeled rates of two commonly used fungicides (propiconazole and chlorothalonil), an insecticide (trichlorfon) and an untreated control. The study was harvested in the subsequent fall, and number of larvae alive in each plot was recorded. In multiple laboratory assays, second and third instar larvae were maintained in cups of soil in a growth chamber. Larvae were treated with maximum-labeled rates of propiconazole, chlorothalonil, trichlorfon, an untreated control, and the formulation blanks (i.e., no active ingredient) for the two fungicides. In the laboratory study, propiconazole resulted in approximately 50% mortality to second instar larvae, however third instars were not adversely affected. Chlorothalonil did not result in significant mortality of any larval instar. In the field study, only trichlorfon resulted in significant mortality of larvae. These results suggest that propiconazole may result in mortality of early-instar larvae, but further study is needed to corroborate these findings in a field setting.
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