Theory for optimizing attract-and-infect methods for pest management

Attract-and-infect systems are gaining attention as alternatives to chemical insecticides in insect pest control. By employing traps that capture males with lures and inoculate them with microbes before releasing them, known as autodissemination traps, pest managers can indirectly target the female portion of the population through horizontal transmission. We developed a theory to assess the potential for pest suppression using entomopathogenic fungi. This study focuses on pests with economically damaging larval stages, particularly tephritid fruit flies. The theory, adapted from a classical SIR framework but assuming no recovery (ie an SI structure), indicates a trade-off between the beneficial impacts of infection on female reproduction or mortality and the detrimental pathogen-induced mortality that reduces infected male mating success. When infection reduces female reproduction, high pathogen-induced mortality hinders the mating success of inoculated males, leading to high larval numbers. However, when there is no reduction in fecundity from infection, some mortality is needed to reduce population growth. If the pathogen-induced mortality is too high, however, infected males are not able to mate, reducing transmission to females, eventually leading to population growth. Thus, the key to attract-and-infect program success may depend on finding the right pathogen that strikes a balance between keeping virulence low enough to allow males to successfully mate, while being virulent enough to kill females or reduce their reproduction.