|Grewal, P - OSU|
|Grewal, S - OSU|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 23, 2002
Publication Date: N/A
Interpretive Summary: White grubs, larvae of scarab beetles, are the most serious pests of turf in the northeastern and central United States and of significant concern in all other areas of the country. In addition the white grubs cause considerable economic damage to nursery plants and are the subjects of state and international quarantines in the nursery and airline industries. There is a considerable need for new, effective, non-chemical measures for controlling these pests. Entomopathogenic nematodes hold great promise as biological alternatives to chemicals for the control of white grubs and other soil-inhabiting insect pests. They are exempt from registration by the Unites States Environmental Protection Agency, possess a broad host range, can be mass produced and have high virulence. However nematodes have been inconsistent in the past. We found that a recently discovered nematode from Australia was the most efficient at killing scarab larvae, but several native strains of nematodes also gave satisfactory results. Not all white grubs are equally susceptible to the nematodes. An introduced species, the European chafer, was most difficult to kill, with other introduced white grubs such as the Japanese beetle and oriental beetle, showing the same susceptibility as our native masked chafer grubs. These results will allow State and Federal agencies, as well as turf and nursery managers, to match the potentially successful nematode with their particular white grub problem. This work shows that European chafer larvae are particularly poor targets at this time for nematode control.
Technical Abstract: Invasive, non-native, white grubs (Coleoptera: Scarabaeidae) cause damage in urban landscapes. Although a lack of natural enemies is often considered as an important factor in the establishment and spread of invasive species, the potential of incumbent generalist parasites and pathogens to delay their establishment and spread has not been explored. We assessed the susceptibility of the non-native species Popillia japonica, Anomala orientalis and Rhizotrogus majalis and the native Cyclocephala borealis to entomopathogenic nematodes from within and outside the geographic ranges of the four scarabs. We found that R. majalis was the least susceptible to entomopathogenic nematodes, whereas P. japonica and A. orientalis were as susceptible as the native C. borealis. Overall, there were no differences in the virulence of the nematode species and strains from within and outside the geographic ranges of either P. japonica or C. borealis. Heterorhabditis zealandica (X1 strain) was significantly more virulent than any other Heterorhabditis species or strain against P. japonica with a LC50 of 272 infective juveniles/grub. Heterorhabditis zealandica also showed the highest penetration efficiency and the lowest encapsulation in P. japonica grubs. Results suggest that the introduction of the non-native H. zealandica into the front-line states with respect to the movement of P. japonica and A. orientalis should be explored as a tactic to delay establishment and spread. The results also suggest that the manipulation of the indigenous H. bacteriophora populations may help in reducing spread and mitigating losses caused by the invasive white grub species.