Fungicides affect Japanese beetle (Coleoptera: Scarabaeidae) egg hatch, larval survival and detoxification enzymes

Larvae of the Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae), have a patchy distribution in soils, which complicates detection and management of this insect pest. Managed turf systems are frequently under pest pressure from fungal pathogens, necessitating frequent fungicide applications. It is possible that certain turfgrass fungicides may have lethal or sub-lethal adverse effects on eggs and larvae of P. japonica that inhabit managed turf systems. In this study, eggs and 1^st, 2^nd, and 3^rd instar larvae were treated with the fungicides chlorothalonil and propiconazole, and survival was compared to untreated controls as well as positive controls treated with the insecticide trichlorfon. Chlorothalonil reduced survival of 1^st instar larvae treated directly, and hatched from treated eggs. Propiconazole delayed egg hatch, reduced the proportion of eggs that successfully hatched, and reduced survival of 1^stinstar larvae treated directly and hatched from treated eggs. Sub-lethal doses of the fungicides lowered the activities of certain detoxification enzymes in 3^rd instar grubs. Fungicide applications to turfgrass that coincide with oviposition and egg hatch of white grubs may have sub-lethal effects. This work is applicable to both high maintenance turfgrass such as golf courses where applications of pesticides are more frequent, and home lawn services where mixtures of multiple pesticides are commonly used.