Potential lethal effects of fungicides on eggs and larvae of 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 low-cutting height, ample exposure to sunlight, and a loose soil medium. A series of toxicity assay were conducted to evaluate whether the commonly-applied turfgrass fungicides propiconazole and chlorothalonil have adverse effects on larvae of P. japonica. Eggs and first, second, and third instar larvae were treated with maximum labeled rates of Banner MAXX II (propiconazole), Daconil Weatherstik (chlorothalonil), and the insecticide Dylox (trichlorfon) as a positive control. Number of days to egg hatch and survival of each instar was compared against untreated individuals. Egg hatch was significantly reduced and delayed in individuals treated with propiconazole, and of the eggs that did hatch, survival was lower than untreated controls. Eggs treated with chlorothalonil were not significantly delayed in hatch timing, but the eggs that hatched had significantly lower survival than untreated controls. For first instar larvae, treatment with chlorothalonil resulted in greater mortality than untreated controls, but propiconazole had no adverse effect. Neither fungicide adversely affected second or third instar larvae. These findings suggest that fungicide applications that coincide with female oviposition periods may result in reduced populations of P. japonica in golf putting greens.