Stage-specific predation on Lygus hesperus affects its population stage structure

Evidence suggests that prey can vary in their susceptibility to predation depending on their developmental stage. Stage-dependent predation is of particular importance to integrated pest management, because it is often a particular developmental stage of a pest that causes the majority of the damage to the crop. An understanding of stage-dependent biocontrol is therefore important for predicting the ultimate impact of herbivore populations. In this article, we addressed this issue by focusing on the stage structure of Lygus hesperus Knight (Heteroptera: Miridae) populations in cotton as related to the density of a specific generalist predator. We first demonstrated in a field experiment that Geocoris spp. adults suppressed L. hesperus eggs and/or early instars (first through third), but did not suppress fourth through fifth instars or adult L. hesperus . We then demonstrated that this stage-specific predation translated into season-long shifts in the stage structure of L. hesperus populations in cotton fields. Using weekly sweep counts across 21 separate cotton fields, we found a negative correlation between season-long Geocoris spp. densities and season-long densities of L. hesperus nymphs. In contrast, there was no such correlation between Geocoris spp. and L. hesperus adults. Taken together, these results suggest that Geocoris spp. predators influence the stage structure of L. hesperus populations in cotton, which in turn has the potential to affect patterns of cotton square damage and sampling bias when monitoring L. hesperus populations.