Rob Morrison, USDA-ARS Appalachian Fruit Research Station
Clarissa Matthews, Shepherd University
Watch the video clip on YouTube at https://www.youtube.com/watch?v=czzwuaqO1ec
In this video, we highlight research being funded by USDA-NIFA OREI program on Brown Marmorated Stink Bugs in Organic Farming Systems.
The goal of this research has been to quantify who the main predators of BMSB egg masses are, the kinds of damage they cause, and link the types of damage to specific predator groups. We have found that feeding damage by predators can be sorted into several different categories. These primarily depend on predator mouthpart morphology (e.g. the structures used for eating) and prey handling behavior (e.g. how predators eat their food).
More recently, this research has expanded to look at how different stages of BMSB have different communities of natural enemies. Ultimately, we hope to be able to better characterize the natural enemy community so that we can start designing landscapes to improve their effectiveness in managing BMSB.
Drs. Rob Morrison and Clarissa Mathews created the video, and Emily Fraser performed the narration. Research technician Brittany Poling made a guest appearance.
When you think of insects, you might think of creepy crawlies infesting your home. But, not all insects are pests. In fact, many insects are beneficial and actually kill pests. These so-called "natural enemies" of pests are naturally-occurring predators or parasitoids that make their living by attacking various stages of other insects, and as a result, are beneficial to you and me.
Researchers studying an invasive pest from Asia, the brown marmorated stink bug, have been facing a dilemma. This smelly bug is a nuisance to homeowners and is wrecking havoc on farms across the mid-Atlantic region where it inserts its straw-like mouthparts into luscious fruits and vegetables, causing major economic losses. To better understand if our native natural enemies are starting to eat this invasive bug, researches have been placing eggs of the pest in agricultural crops and waiting to see what happens.
It was expected that parasitoids would attack the stink bug’s eggs. However, researchers have been noticing inexplicable damage to the eggs that is not caused by parasitoids. Increasingly, scientists have begun to think this damage may be caused by another natural enemy -- the predators.
Because it is not possible to watch the BMSB eggs while they are exposed in the field, we’ve embarked on a case of entomological whodunit. Think CSI meets Bill Nye. In the lab, we have been carefully photographing egg masses before allowing specific predators to feed, and then taking photographs afterwards to document specific types of damage caused by specific predator groups. This catalogue of photos will be helpful to ascribe certain types of egg damage we see in the field to specific predator groups and will help us quantify the impact of native predators in controlling BMSB populations.
Here are some highlights. It turns out that the way that a predator eats its dinner is important for the fate of an egg mass. Some predators, such as jumping spiders will completely remove an egg mass from the substrate, invert it, and eat the eggs individually, very slowly sucking the fluids out of the egg, with many of the eggs remaining after it is done.
Other predators, such as earwigs, are voracious and will mostly devour an egg mass, leaving only small fragments of egg shells, but still in the restricted area of the original egg mass. Yet other predators will pull off eggs individually, consume them, drop the remains elsewhere and repeat, such as ground beetles.
The damage caused to an egg mass, number of eggs affected, pattern of fragmentation, and sometimes whether an egg mass in the field is even present when retrieved, can all suggest a specific predator group. This information can be used by other researchers to get a better idea of the good work our native predators are doing to help control the invasive BMSB.
Our work has expanded more generally to understand how the native predator communities use different stages of BMSB. For instance, while assassin bugs won’t eat the eggs, they will readily attack the nymphs. Other predators, for example, the predatory spined soldier bug, eats eggs AND nymphs of the pest.
Ultimately, we hope this research will allow us to identify key predator groups, so we bolster these natural enemies in the field, and in the end, stop the stink bug invasion.