Penetration of the entomopathogenic nematode heterorhabditis spp. into host insects at 9 and 20 degreesC
Biological control of black vine weevil, Otiorhynchus sulcatus, by means of the entomopathogenic nematode, Heterorhabditis spp., is difficult to obtain at low temperatures. The influence of temperature on nematode penetration ability was investigated to identify whether this process is a bottleneck for biocontrol. Variation in penetration ability among and within Heterorhabditis was assessed. A negative exponential model was used to characterize penetration in time. The two parameters in this model, the proportion of infectious nematodes and their relative penetration rate, were compared among different batches of the same nematode isolate (HF85). There was a considerable amount of nongenetic variation among batches of HF85, stored for different periods of time, in the proportion of infectious nematodes, but there was little variation in the relative penetration rate. There was almost no (genetic) variation in the proportion of nematodes that is infectious against O. sulcatus at 9 degreesC among 12 heterorhabditid isolates. Variation did occur when two lepidopteran species, Galleria mellonella and Spodoptera exigua, were offered as hosts at 9 degreesC or when hosts were presented at 20 degreesC. The relevance of variation in penetration parameters for control of O. sulcatus at low temperatures is discussed. Copyright 1998 Academic Press.
Westerman
PR
Van Hall Instituut, 8901 BV Leeuwarden, The Netherlands.