Recruitment of Diabrotica speciosa and an entomopathogenic nematode to aboveground application of elicitors: applications for biocontrol

Understanding the connection between plant defense systems above and belowground and the effects of those systems on pests and natural enemies holds great potential for designing effective control strategies.  Here we investigate the tritrophic interactions between corn plants treated aboveground with elicitors, adults of Diabrotica speciosa, a polyphagous pest of many agricultural crops including corn, and Heterorhabditis amazonensis, an entomopathogenic nematode and subterranean natural enemy of D. speciosa larvae.  The response of D. speciosa and H. amazonensis were evaluated independently in olfactometers to all pairwise combinations of corn plants with mechanical damage, pest damage, foliar methyl jasmonate treatment, foliar methyl salicylate treatment, and control (no treatment, no damage).  While mechanical damage and methyl jasmonate treatment did not significantly recruit large numbers of either species, both pest damaged plants and those treated with methyl salicylate were more attractive to D. speciosa and H. amazonensis.  The enhanced recruitment to pest damaged and methyl salicylate treated plants suggests that aboveground stimulation of corn defenses holds ramifications for belowground multitrophic interactions, suggests that this elicitor may produce induced susceptibility, and provides an option for augmenting volatile mediated crop management strategies.