The combined effects of pathogens and predators on insect outbreaks

The economic damage caused by episodic outbreaks of forest-defoliating insects has spurred much research1, yet why such outbreaks occur remains unclear2. Theoretical biologists argue that outbreaks are driven by specialist pathogens or parasitoids, because host–pathogen and host–parasitoid models show large-amplitude, long-period cycles resembling time series of outbreaks3,4. Field biologists counter that outbreaks occur when generalist …