Susceptibility of cabbage root maggot, Delia radicum, to entomopathogenic nematodes (Steinernematidae and Heterorhabditidae)

Abstract

Susceptibility of last ins tar maggots of Delia radicum to 13 isolates of five 5teinernema (5. feltiae, 5. carpocapsae, 5. affine, 5. arenarium and 5. glaseri) and four isolates of Heterorhabditis (H. megidis and H. bacteriophortl) was evaluated in the laboratory. Each of the populations controlled the maggot to some extent but differed in efficiency. When exposing one maggot to ten infective juveniles (IJs), 5. feltitle isolates showed the highest efficiency: 12-32% mortality at two days after infection (dail and 26- 73 % mortality at four dai. 5. gltlseri had the lowest pathogenicity (5.6% mortality at four dai), whereas 5. CtlrpOCtlpstle,5. tlffine, 5. tlrentlrium, H. megidis, and H. btlcteriophora were intermediately active (8-20% mortality at four dai). Comparisons of 5. feltitle populations showed Lxm31 as the best performing one. Experiments in which last instar maggots were exposed during 48 hrs to 12,25,50, 100, or 200 lJs yielded a LDso of 5. feltitle Lxm31, 5. ctlrpoctlpstle All,S. tlrentlrium, H. megidis Sn5 and H. btlcteriophora NJ-hbr of 12, 102, 258, 196, and 344 1J s per larva, respectively. As the effect of 5. gltlseri on maggots was too weak, a linear relation between dose and mortality was not found. The LTso for 5. feltitle Lxm31, 5. ctlrpoctlpstle All,S. tlrentlrium, H. megidis Sn5 and H. btlcteriophorcz (NJ-hbr) was calculated at 17, 82,192,77, and 104 hours per larva, respectively.