38th Annual Meeting of the Society for Invertebrate Pathology

The European chafer (EC) is the most damageable white grub species in Quebec. Heterorhabditis bacteriophora is widely recommended and applied for EC control on turf in eastern Canada. Our objective was to compare the virulence of five commercial isolates of H. bacteriophora against an EC population from Quebec. In the laboratory, four separated trials against the third-instar EC grubs were performed in 30-cm³ plastic Solo cups at 24C. Nematodes were applied on a sandy soil at 0, 600, and 2000 IJs/larva/cup rates. After a 4-day exposure time, mortality was recorded on day 4, 6 and 10. In a greenhouse trial, nematode treatments were performed in plastic trays established with Kentucky bluegrass (1-month growth) on a sandy soil. Nematodes were applied at the single rate of 16,000 IJs/30 larvae/tray (1.5 billion IJs/ha) and insect mortality was recorded 20 days post-treatment. In the laboratory, highly variable mortality rates were recorded between trials and between commercial isolates, ranging from 0 to 47%. With most isolates, no significant increase in mortality was recorded when increasing the nematode rate from 600 to 2000 IJs. In the greenhouse trial, mortality rates caused by H. bacteriophora were very similar to the ones recorded in the cups, ranging from 19 to 42%.