CSI egg mass damage: Tracking down unexplained predation of brown marmorated stink bug egg masses by native natural enemies

Background/Question/Methods

The brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive, highly polyphagous agricultural and nuisance pest in the United States. In coordinated trials throughout the eastern United States, sentinel egg masses have been deployed for monitoring parasitism and predation by native natural enemies for H. halys.  In a significant portion of these trials, there was unexplained loss of the egg mass, or damage incurred from an unknown source to eggs.  The goal of the current study was to characterize the appearance of native predator damage to H. halys egg masses in order to provide resources for identifying damage from specific predators to sentinel egg masses in the mid-Atlantic.  Predators were mostly field-collected from local agricultural landscapes where H. halys is sympatric, or in a few cases, were obtained from commercial insect supply companies.  In some cases, both adult and immature stages of predators were tested.  Predators were held for at least 24-hours prior to assays in order to induce starvation.  Afterwards, predators were placed individually with a H. halys egg mass that was either fresh (<24 hrs old), 2 d old (24-48 hrs old), or frozen, and the predator was allowed to feed for 48 hrs.

Results/Conclusions

Over 25 insect taxa were evaluated as predators of H. halys eggs, and a photographic library of egg mass damage from specific predators was systematically developed, as well as video recordings of predator feeding behavior. The predators most commonly found feeding on the eggs were katydids (where 93% fed), Harpalus spp. (88% fed), jumping spiders (44% fed), and earwigs (40% fed). The type of damage inflicted on an egg and the number of eggs consumed during the trial period depended on both the arthropod’s mouthpart morphology and its behavior in handling the egg mass.  Eggs exhibited characteristic damage patterns depending on the feeding guild of the predator. Our results suggest that a large portion of the inexplicable egg loss in the field and uncharacterized damage in previous sentinel egg mass studies may be the result of native predators that have recently switched to use H. halys as a new prey species.