By Josh Lancette
There’s a relatively new pest of soybean in town. Its name? Megacopta cribraria, but most folks call it the kudzu bug. If left unchecked, the bug has been shown to cause up to 60% yield loss in soybean fields.
In order to help manage this pest, researches at North Carolina State University have published an open-access guide on the ecology of kudzu bug and different management strategies. The paper is freely available in the Journal of Integrated Pest Management.
The kudzu bug was first discovered in the United States in 2009 in Georgia. The insect is native to Southeast Asia, and is closely associated with kudzu, an invasive climbing plant that Bill Finch dubbed America’s most infamous weed.
While kudzu was introduced to the United States as a garden novelty plant in the late 19th century, the kudzu bug is believed to have entered the country as a stowaway. In fact, the population in the United States shows a single female lineage to the Kyushu region of Japan.
Since it was discovered in Georgia, it has been found in Alabama, Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and the District of Columbia.
The bug is known as a piercing-sucking pest. The adults use their mouthparts to pierce and feed on the plant sap from the stem, petioles, and nodes of soybean and kudzu, preferring tender new growth to older growth, and this feeding results in decreases in the number and weight of seeds per pod. They are related to stink bugs and release a foul odor when threatened or crushed, a particular nuisance to people whose houses the bugs aggregate on in the winter.
“We hope that through this paper, the tools available for soybean growers to manage kudzu bug can be focused on, and that the logic behind management recommendations can be clarified,” said Sriyhanka Lahiri, one of the co-authors. “This is especially important because this soybean pest continues to spread through the United States, and more and more piercing-sucking pests of field crops are being discovered.”
In the paper, the authors discuss a few tips and bits of information on managing the kudzu bug:
- Start at the edges. Kudzu bugs tend to aggregate near edges of fields rather than in the middle of fields. So, when scouting a field for the presence of kudzu bugs, edges should be searched first, and if the bugs are found there, scouting through the whole field should continue.
- Type of field is important. Fields where soybeans are planted early, fields that are conventionally tilled, and fields that have narrow rows have an increased risk of containing damaging levels of kudzu bug.
- Sweep those nets. Sweep net sampling, with a focus on kudzu bug nymphs, is an effective way to monitor a field. If the density of bugs is more than one nymph per sweep, insecticides should be used.
- Which insecticide? Bifenthrin is the most effective insecticide. However, bifenthrin also kills predators and parasites of kudzu bug, so it is best to use it as part of a broader IPM strategy.
- It has enemies. Many native insects are predators or parasites of kudzu bug. Most notably, Paratelenomus saccharalis is an egg parasitoid specific to kudzu bugs and is being considered as a biological control agent.
- Resistance is possible. Some soybeans varieties have been shown to be resistant to kudzu bugs. Using these varieties will help reduce the need for insecticides and can promote a healthier environment.
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Josh Lancette is Manager of Publications at the Entomological Society of America.