When 'Calls for Help' Backfire: Induced Plant Volatiles Reduce the Attraction of a Nocturnal Predator in Sugarcane.

While herbivore-induced plant volatiles are well-established cues that guide natural enemies to herbivores in ecosystems, microbe-induced plant volatiles have recently gained attention as promising tools for achieving similar outcomes. However, how nocturnal predators respond to volatile cues induced by herbivory and/or endophytic fungal remains poorly understood, particularly in systems where the predator and plant do not share a tightly co-evolved or highly specialized relationship. To explore this, we investigated whether Spodoptera frugiperda infestation and Metarhizium robertsii endophytic colonization in sugarcane plants could enhance the olfactory attraction of the nocturnal earwig predator Doru luteipes by modifying nocturnal volatile emissions and altering endogenous levels of jasmonic acid and salicylic acid. Unexpectedly, the changes in volatile emissions and phytohormone levels induced by herbivory and microbial colonization led to a reduced attraction of the predator compared with undamaged control plants and with the no-plant control. These findings highlight the complexity of D. luteipes' responses to induced indirect defenses in sugarcane, suggesting that such strategies may not consistently enhance the recruitment of natural enemies.