Search

Turfgrasses hosts a diverse community of predators that contribute to herbivore suppression. However, there is little evidence that predators directly consume a common turfgrass herbivore, the billbug (Sphenophorus sp.) (Coleoptera: Curculionidae). Given low rates of direct consumption by predators, prospects for strong non‐consumptive effects in billbugs were underappreciated. However, this assumed lack of non‐consumptive effects presupposes that herbivorous prey, like billbugs, can identify predators and the level of threat that they pose. Here, we examined this assumption and quantified the extent to which exposure to predators and predator cues altered the behavior (predator avoidance, feeding, and mating) of bluegrass billbug, Sphenophorus parvulus Gyllenhal. First, using a series of behavioral assays within microcosms, we exposed billbugs to predators – Pterostichus melanarius (Illiger) (Coleoptera: Carabidae), Harpalus sp. (Coleoptera: Carabidae), Philonthus sp. (Coleoptera: Staphylinidae), and Hogna sp. (Araneae: Lycosidae) – singly and in combination to measure the effect of contact with predators and potential synergy among predator species pairs. Indirect exposure to predators, predator odor, and non‐predatory arthropods were also used to measure effects of various predator cues on billbug behavior. In subsequent Y‐tube choice assays we determined whether billbugs discriminated between filtered air and predator odor to isolate chemical signaling as a potential mechanism for billbug predator detection. Direct exposure to predators increased billbug predator avoidance (up to 201%), and decreased billbug feeding (down to −78%), though no predation was observed. Similar behavioral changes were observed when billbugs were exposed indirectly to a predator, and to predator odor. In Y‐tube assays billbugs avoided predator odor, further suggesting billbugs use chemical cues to detect predator presence and that these may be a driver in their observed behavior. Our results show that billbugs exhibit strong non‐consumptive effects, even in the absence of strong direct consumptive effects. These results provide the foundation for further research concerning the role of chemical signaling in billbug predator detection. [ABSTRACT FROM AUTHOR]

Pioneer herbivorous insects may find their host plants through a combination of visual and constitutive host-plant volatile cues, but once a site has been colonized, feeding damage changes the quantity and quality of plant volatiles released, potentially altering the behavior of conspecifics who detect them. Previous work on the pepper weevil, Anthonomus eugenii Cano (Coleoptera: Curculionidae), demonstrated that this insect can detect and orient to constitutive host plant volatiles released from pepper [ Capsicum annuum L. (Solanaceae)]. Here we investigated the response of the weevil to whole plants and headspace collections of plants damaged by conspecifics. Mated weevils preferred damaged flowering as well as damaged fruiting plants over undamaged plants in a Y-tube olfactometer. They also preferred volatiles from flowering and fruiting plants with actively feeding weevils over plants with old feeding damage. Both sexes preferred volatiles from fruiting plants with actively feeding weevils over flowering plants with actively feeding weevils. Females preferred plants with 48 h of prior feeding damage over plants subjected to weevil feeding for only 1 h, whereas males showed no preference. When attraction to male- and female-inflicted feeding damage was compared in the Y-tube, males and females showed no significant preference. Wind tunnel plant assays and four-choice olfactometer assays using headspace volatiles confirmed the attraction of weevils to active feeding damage on fruiting plants. In a final four-choice olfactometer assay using headspace collections, we tested the attraction of mated males and virgin and mated females to male and female feeding damage. In these headspace volatile assays, mated females again showed no preference for male feeding; however, virgin females and males preferred the headspace volatiles of plants fed on by males, which contained the male aggregation pheromone in addition to plant volatiles. The potential for using plant volatile lures to improve pepper weevil monitoring and management is discussed. [ABSTRACT FROM AUTHOR]