Entomopathogen and Synthetic Chemical Insecticide: Synergist and Antagonist

Abstract

The use of synthetic insecticides and biological agents are the main tools to control agricultural pests, each with its own advantages and disadvantages. Although the use of chemical compounds is inevitable in some cases, attitudes of consumers and agricultural experts towards healthy products and lower environmental contamination have increased the prevalence and preference for biological agents. Among them, insect pathogens have been considered as the unique and widely distributed components in many ecosystems, due to their diverse virulent mechanisms. The entomopathogenic fungi (EF) and nematodes have been commercialized as biologically active insecticides against a wide range of pests. Although many environmental benefits for these compounds have been identified, the disadvantages such as low virulence due to behavior or habitat of target pest, delayed killing performance and sensitivity to environmental factors, lead to simultaneous use of entomopathogens with one or more chemical insecticides in reduced doses. In this review, the possibility of simultaneous use of chemical insecticides from different classes with EF and nematodes were discussed by indicating severally up-to-date studies. The effects of insecticides on cessation or induction of germination and conidiation of fungi have been reported, depending on the concentrations of used chemicals. Field or laboratory experiments have shown synergism or antagonism of EF with some insecticides. In case of entomopathogenic nematodes, the effects of insecticides from different classes have been investigated on mobility and survival of nematodes, as well as on synergistic or additive effects. Generally, the possibility of simultaneous use of chemical insecticides with these two groups of entomopathogens depends on target pest, spraying method, insecticide class or formulation and origin of entomopathogens.