Greenhouse and field evaluations of entomopathogenic nematodes (Nematoda:Heterorhabditidae and Steinernematidae) for control of cabbage maggot (Diptera:Anthomyiidae) on cabbage.

Abstract

Entomopathogenic nematodes--Heterorhabditis bacteriophora Poinar (Oswego strain), Steinernema carpocapsae (Weiser) (NY001 strain), Steinernema carpocapsae (25 strain), Steinernema feltiae Filipjev (= Neoaplectana carpocapsae Weiser) (369 strain), Steinernema feltiae (27 strain), and Steinernema riobravus Cabanillas and Poinar (355 strain)--were examined for pathogenicity against cabbage maggot, Delia radicum (L.), larvae 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 infective juveniles of S. feltiae (27 strain) reduced the number of D. radicum that developed to pupae on potted cabbage plants. H. bacteriophora (Oswego) at applications of 3,000 and 30,000 infective juveniles per 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 between 100 and 100,000 infective juveniles per plant of S. feltiae (27 strain) linearly reduced the number of D. radicum pupae that developed on potted cabbage plants and the damage caused to the roots by D. radicum larvae. Root and stem dry weights of cabbage plants infested with D. radicum were significantly greater for plants inoculated with 100,000 infective juveniles of S. feltiae (27 strain) than for plants not inoculated with nematodes. Nematode inoculation did not prevent significant losses in root or stem dry weights at dosages less than 100,000 infective 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 natural or augmented populations of D. radicum larvae on cabbage in the field. However, mortality rates of wax moth larvae exposed to soil samples treated with S. feltiae (27 strain) suggested that this nematode showed greater persistence when applied beneath rather than on the soil surface.