Laboratory Evaluation of Selected Chemicals as Antidesiccants for the Protection of the Entomogenous Nematode, Steinernema feltiae (Rhabditidae: Steinernematidae), Against Lymantria dispar (Lepidoptera: Lymantriidae)

The entomogenous nematode Steinernema feltiae is very sensitive to drying, which limits its usefulnessas an effective biological control agent. In the laboratory, materials were not only evaluated on their ability to retard evaporation, but on their biological activities against the host insect, Lymantria dispar (L.), as well as the nematode, S. feltiae Filipjev. Eighty-eight materials were tested for their ability to retard evaporation during a 19-h drying period. Sixty-seven materials were no more effective than water, while 21 materials were effective in retarding evaporation. Base oil, folicote, and sag 470 (at 1–10%); foam fighter F, glycerol, and klearol (at 2.5–10%); 2251 oil (at 5–10%); and several oils (at 10%) were effective antievaporants. While some of the materials were nontoxic to L. dispar larvae (folicote, sag 470, and glycerol), some showed moderate toxicity (mineral oil, Sunspray oil, and orchex Exxon), and others were extremely toxic (pyronyl oil and Savol oil). Under severe drying conditions, some of the materials had an adverse effect upon S. feltiae infective nemas (klearol, base oil, orchex Exxon, and orchex 796W); upon nema-progeny production (foam fighter F); or upon the host, the nema, and hema-progeny production (base oil and orchex 796W). In some cases, however, nema-progeny production was unaffected despite some (mineral oil) or high (klearol and orchex Exxon) host (=insect) mortality. Only folicote and, to a lesser extent, mineral oil appeared to have little adverse effect upon the host as well as the nematode parasite.