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 the
biopesticides (Bio-arc, Bio-zeid and Nemex) on viability and infectivity of infective juveniles (IJs) of
the two entomopathogenic nematodes (EPNs) viz., Heterorhabditis bacteriophora (HP88 strain) and
Steinernema carpocapsae (All strains) were assessed under laboratory conditions against the six instar
larvae of Galleria mellonella L. Results indicated that one day after treatment, the tested pesticides
reduced the viability of IJs by 9.83 to 23.00% depending on the pesticide and nematode species. After
two days, IJs mortality was obviously increased to reach 23.00, 37.50 and 38.33% with the chemical
pesticides abamectin, fenamiphos and oxamyl, respectively at the recommended doses. At half
recommended doses, IJs mortality reached 14.50, 20.16 and 29.00%, respectively for the same
pesticides. Whereas, the parallel values in abamectin, fenamiphos, and oxamyl at the seventh day were
42.83, 63.16; 74.17, 91.83 and 74.00, 86.16% at the half and recommended dose, respectively, after
the seventh day, fenamiphos was the most toxic among the tested chemical pesticides followed by
oxamyl and abamectin.The biopesticides Bio-arc (Bacillus megaterium), Bio-zeid (Trichoderma
album) and Nemex (Serratia marcescens) on IJs mortality of H. bacteriophora and S. carpocapsae
were less toxic as compared to chemical pesticide. After seven days of treatment, at the recommended
and 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 tested
biopesticides followed by Bio-arc and Bio-zeid. Results indicated that the pesticides screened for their
compatibility 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. The
additive effect took place for most of the tested treatments, while the antagonistic effect was detected
in 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 by
choosing an appropriate time-intervals between nematode and pesticide applications.