COMPATIBILITY OF ENTOMOPATHOGENIC NEMATODES, Heterorhabditis bacteriophora Poimar AND Steinernema carpocapsae Weiser WITH SOME CHEMICAL AND BIOPESTICIDES

Effect of the nematicides (abamectin, fenamiphos and oxamyl) as well as thebiopesticides (Bio-arc, Bio-zeid and Nemex) on viability and infectivity of infective juveniles (IJs) ofthe two entomopathogenic nematodes (EPNs) viz., Heterorhabditis bacteriophora (HP88 strain) andSteinernema carpocapsae (All strains) were assessed under laboratory conditions against the six instarlarvae of Galleria mellonella L. Results indicated that one day after treatment, the tested pesticidesreduced the viability of IJs by 9.83 to 23.00% depending on the pesticide and nematode species. Aftertwo days, IJs mortality was obviously increased to reach 23.00, 37.50 and 38.33% with the chemicalpesticides abamectin, fenamiphos and oxamyl, respectively at the recommended doses. At halfrecommended doses, IJs mortality reached 14.50, 20.16 and 29.00%, respectively for the samepesticides. Whereas, the parallel values in abamectin, fenamiphos, and oxamyl at the seventh day were42.83, 63.16; 74.17, 91.83 and 74.00, 86.16% at the half and recommended dose, respectively, afterthe seventh day, fenamiphos was the most toxic among the tested chemical pesticides followed byoxamyl and abamectin.The biopesticides Bio-arc (Bacillus megaterium), Bio-zeid (Trichodermaalbum) and Nemex (Serratia marcescens) on IJs mortality of H. bacteriophora and S. carpocapsaewere less toxic as compared to chemical pesticide. After seven days of treatment, at the recommendedand half recommended doses, IJs mortality reached to 63.00, 43.66; 45.49, 41.66 and 42.83, 34.17%with Nemex, Bio-arc and Bio-zeid, respectively. Nemex was the most toxic among the testedbiopesticides followed by Bio-arc and Bio-zeid. Results indicated that the pesticides screened for theircompatibility with H. bacteriophora and S. carpocapsae in controlling the 6th instar larvae of G.mellonella showed an additive or antagonistic reactions. No evidence of synergy was observed. Theadditive effect took place for most of the tested treatments, while the antagonistic effect was detectedin combinations of H. bacteriophora with oxamyl, S. carpocapsae with fenamiphos and both of S.carpocapsae and H. bacteriophora with Nemex. Incompatibility in these cases can be managed bychoosing an appropriate time-intervals between nematode and pesticide applications.