GREENHOUSE AND FIELD EVALUATIONS OF ENTOMOPATHOGENIC NEMATODES (NEMATODA, HETERORHABDITIDAE AND STEINERNEMATIDAE) FOR CONTROL OF CABBAGE MAGGOT (DIPTERA, ANTHOMYIIDAE) ON CABBAGE

Entomopathogenic nematodes-Heterorhabditis bacteriophora Poinar (Osweg o strain), Steinernema carpocapsae (Weiser) (NY001 strain), Steinernem a carpocapsae (25 strain), Steinernema feltiae Filipjev (=Neoaplectana carpocapsae Weiser) (369 strain), Steinernema feltiae (27 strain), an d Steinernema riobravus Cabanillas and Poinar (355 strain)--were exami ned for pathogenicity against cabbage maggot, Delia radicum (L.), larv ae in the greenhouse and field. Applications (per plant) of 3,000 and 4,000 infective juveniles of S. feltiae (369 strain), 30,000 infective juveniles of H. bacteriophora (Oswego strain), and 300 and 30,000 inf ective juveniles of S. feltiae (27 strain) reduced the number of D. ra dicum that developed to pupae on potted cabbage plants. H. bacteriopho ra (Oswego) at applications of 3,000 and 30,000 infective juveniles pe r plant and S. feltiae (27 strain) at applications of 30,000 (but not 3,000) infective juveniles per plant significantly reduced root damage caused by larvae of D. radicum. Logarithmically increased dosages bet ween 100 and 100,000 infective juveniles per plant of S. feltiae (27 s train) linearly reduced the number of D. radicum pupae that developed on potted cabbage plants and the damage caused to the roots by D. radi cum larvae. Root and stem dry weights of cabbage plants infested with D. radicum were significantly greater for plants inoculated with 100,0 00 infective juveniles of S. feltiae (27 strain) than for plants not i noculated with nematodes. Nematode inoculation did not prevent signifi cant losses in root or stem dry weights at dosages less than 100,000 i nfective juveniles per plant. Soil surface applications of 100,000 and 200,000 infective juveniles per plant of S. feltiae (27 strain) were more effective than subsurface applications in preventing damage by na tural or augmented populations of D. radicum larvae on cabbage in the field. However, mortality rates of wax moth larvae exposed to soil sam ples treated with S. feltiae (27 strain) suggested that this nematode showed greater persistence when applied beneath rather than on the soi l surface.