Host-pathogen interactions of the two native isolates of Beauveria bassiana to a predatory coccinellid, Cryptolaemous montrouzieri Mulsant (Coleoptera: Coccinellidae)

Abstract

Fungi are among the most important microorganisms affecting population dynamics of insects. Although they are used as biocontrol agents for several decades but their interactions to insect pests, predators and parasitoids are still interesting in case of virulence, host physiology and environmental persistence. Understanding the possible synergistic or antagonistic interactions of entomopathogenic fungi with other biocontrol agents mainly predators is a critical factor to achieve a successful pest control program. In the current study, effects of the two native isolates of Beauveria bassiana (AM-118 and BB3) were studied on survival, cellular immunity and antioxidant system of Cryptolaemous montrouzieri Mulsant. Bioassay results showed that both AM-118 and BB3 caused significant mortality on the third instar larvae and the adults of C. montrouzieri. Moreover, they increased total and differential hemocyte counts and significantly induced phenoloxidase activity and nodule formation at 48, 72 and 96 h post-treatment. A considerable increase was also observed in the activities of antioxidant enzymes at 72 and 96 h post-treatment. Although the isolates caused mortality on both stages, induction of immune and antioxidant systems protect C. montrouzieri against infective conidia.