The introduction of glass cylinders and plastic nets in olfactometers facilitates the entomopathogenic nematode behaviour tests

Abstract

It was evaluated the adequacy of an olfactometer, to which a glass cylinder and a plastic net were introduced to avoid displacement of the target insect larvae, allowing determining displacement and infection capacity of infective juveniles (IJ) of entomopathogenic nematodes in laboratories trials. For these assays, recently emerged IJ with 100 % viability of the strain HC1 of Heterorhabditis amazonensis Andaló et al. were used. For the assembly of the two branches device, some parts of a six arms olfactometer, glass cylinders, plastic meshes, and, as substrate, sterile silica sand with 10 % of humidity were used. The last instar larvae of Galleria mellonella (L.) use as the target insect came from a laboratory rearing and weighed about 200 mg. A 2000 IJ suspension was applied to the substrate on the end opposing to the PVC tube in which the G. mellonella larvae were kept in a glass cylinder protected with a plastic net to avoid their movement. Three replicas were kept at 27°C. Larval mortality was recorded at 24, 48, and 72 hours after nematode application. With the olfactometer assay, e it was checked mobility of IJ, which moved along 19.5 cm in 60 hours. Mortality of G. mellonella larvae reached 84.7 %. The two-branch olfactometer with the introduction of a glass cylinder and a plastic net, was useful for laboratory studies related to the effect of abiotic factor on entomopathogenic nematodes.