Effects of some botanical insecticides on wheat insects and their natural enemies in winter and spring wheat abstract
The efficacy of range of compounds: one botanical insecticide (NeemAzal T/S) and two pyrethroid insecticides, lambda-cyhalothrin (Karate 9.4% S.C) and deltamethrin (Decis 2.8% E.C.) were evaluated to control Rhopalosiphum padi (L.) and Metopolophium dirhodum (Wlk.) in laboratory; as well as to control frit fly, Oscinella frit (L.). The later insect was also controlled companying with three species of entomopathogenic nematodes (EPNs) (Steinernema carpocapsae, S. feltiae and Heterorhabditis bacteriophora). Management of wheat midges with different botanicals was also studied; Karate (pyrethroid), Biscaya (neonicotinoid) and NeemAzal T/S (botanical insecticide) which were sprayed on wheat at heading stage (GS 55). Different concentrations were used to study efficiency of the tested compounds on both aphid species 24, 48 and 72 hours post treatment in the laboratory. While frit fly and wheat midges were managed in winter and spring wheat fields and evaluated after 3, 7 and 15 days after botanicals application. Surveying wheat insects and the associated natural enemies were inspected before and after treating of botanical insecticides. The mortality reached 100% after 24 h in M. dirhodum and after 48 h in R. padi. Most of the tested compounds caused acceptable levels of cereal aphid’s control. All treatments induced reduction in frit fly infestation and increased larval mortality as well. Populations of frit-fly larvae were lower in the treated than untreated plots. H. bacteriophora was more efficacious against O. frit in laboratory than S. carpocapsae, while the latter was more efficient in field experiments. Karate resulted in significantly lower population densities of frit fly. Insecticide applications to fields of midge-infested winter wheat significantly reduced the wheat midge damage. There were significant differences in wheat midge numbers between treated and untreated. Lacewings and dance flies were more susceptible; while spider, syrphids and parasitoid wasps were more tolerant. The results indicated that the tested compounds were effective against frit fly, aphids, thrips, leafhoppers and wheat midges; and may be used as alternative control methods in IPM programs. Compatibility between natural insecticides and natural enemies is highly required to keep the environment clean.