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Introduction
A co-evolutionary arms race occurs between insects and their pathogens. Whereas selection on the pathogen is for greater exploitation of the host, selection on the host is for greater exclusion of the pathogen (Bush et al. 2001; Roy et al. 2006). The evolution of this behaviour and a description of some of the diverse interactions that occur between arthropods and fungi have recently been described in a review by Roy et al. (2006). Whilst these interactions are of great interest to evolutionary biologists, understanding the fundamental behavioural processes that occur between insects and pathogens is also essential for insect pathologists who wish to exploit fungal entomopathogens as biological control agents. Several species of entomopathogenic fungi are currently available as formulated bio-pesticides, including; Vertalec® (Lecanicillium longisporum ((Petch) Zare & Gams Zimmerman)) (Ascomycota: Hypocreales), BotaniGard® (Beauveria bassiana (Balsamo) Vuillemin) (Ascomycota: Hypocreales) and Green Muscle® (Metarhizium anisopliae var. acridum (Metsch.)) (Ascomycota: Hypocreales) (Milner 1997; Shah and Pell 2003). In addition, non-formulated species of entomopathogenic fungi such as Pandora neoaphidis (Remaudière & Hennebert) Humber (Zygomycota: Entomophthorales) are also being assessed for inclusion as part of integrated pest management schemes. The overall success of using entomopathogenic fungi as biological control agents is affected by numerous abiotic and biotic factors, including the behavioural response of the target insects towards the entomopathogen. This paper describes pre- and post-contact responses of insects to entomopathogenic fungi that are under development as biological control agents. Transmission and vectoring of entomopathogenic fungi to uninfected hosts is then described along with the use of dissemination devices designed to attract and contaminate insects with fungi.
Response of insects to entomopathogenic fungi
Insects and entomopathogenic fungi are under opposing selection pressures. Insects gain a selective advantage from detecting and avoiding fungal pathogens while successful infection of an insect by an entomopathogen requires contact to be made between the host and the pathogen. The behaviour of insects can influence whether contact is made, with changes in activity increasing or decreasing the likelihood of infection (Cory and Hoover 2006). An insect may gain a selective advantage if it is able to detect the risk of attack from entomopathogenic fungi and respond via behavioural avoidance or through post-contact responses such as grooming (Chouvenc et al. 2008). This...