Submitted to: International Congress of Nematology
Publication Type: Abstract only
Publication Acceptance Date: 8/1/2002
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Invasive white grubs cause significant damage in urban landscapes. Although the lack of natural enemies in their new home is often suggested 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 compared the susceptibility of the introduced Popillia japonica and the native Cyclocephala borealis to 16 species and strains of entomopathogenic nematodes isolated from within or outside the geographic ranges of the two scarabs. We found large variation in the virulence of the species/strains of nematodes with over 50% mortality of P. japonica produced by Heterorhabditis zealandica strain XI and H. bacteriophora strain GPSll and of C. borealis by H. zealandica and H. bacteriophora strains KMD 10 and NC 1. H. indica and H. marelatus caused less than 20% mortality of both scarab species. When considered as a group, the nematode species and strains from within and outside the geographic ranges of either P. japonica or C. borealis did not differ in virulence towards either scarab species. Dose response studies against P. japonica and two additional non-native species Anomala orientalis and Rhizotrogus majalis and the native C. borealis indicated that R. majalis was the least susceptible and P. japonica and A. orientalis were as susceptible as C. borealis. H. zealandica was significantly more virulent against P. japonica with a LC50 of 272 infective juveniles/grub. H. zealandica also showed the highest penetration efficiency and the lowest encapsulation in grubs. Results suggest that the introduction of the exotic 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 their establishment and spread. The results also suggest that the manipulation of the indigenous H. bacteriophora populations may help in delaying spread and mitigating losses caused by the invasive grub species.