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Research Highlights

Research Highlights
Beneficial Insects Protect New Jersey Soybean Yields

By Laura Temple

The Mexican bean leaf beetle is one of the few destructive species in the ladybird beetle family, and it likes to eat beans of all types, including soybeans. Its larvae devour leaf tissue between veins, giving plants a lacy appearance. Though it can be a problem throughout soybean production regions, soybean farmers in New Jersey have been battling the Mexican bean leaf beetles for decades.

“Mexican bean leaf beetles produce webbing, and I can remember seeing soybean fields in the 1980s that looked like they had frost on them in July because of heavy infestations,” says Wayne Hudson, an entomologist for the New Jersey Department of Agriculture’s Phillip Alampi Beneficial Insect Laboratory. “Our monitoring and beneficial insect release program allows us to reduce the population of this pest every year.”

A program supported by the New Jersey Soybean Board for years allows Hudson and his team to monitor 50 soybean fields in south and central New Jersey every season for Mexican bean leaf beetles and other invasive insects. In 2020, 32 farmers participated in the program.

“We scout participating fields weekly throughout the soybean growing season, and when Mexican bean leaf beetle larvae populations reach the threshold, we release a beneficial parasitic wasp called Pediobis fovelolatus in the fields to control them,” Hudson explains.

The wasps, native to India, lay eggs in Mexican bean leaf beetle larvae. As parasites, the wasp eggs and larvae consume the bean leaf beetle larvae, but they don’t damage soybeans or other bean crops.

“A week to 10 days after a release, we see results in the field, effectively knocking out much of the second generation of the pest and protecting soybean yields,” Hudson says. “Research and experience shows that one wasp release will reach a 5-mile radius.”

The wasps don’t overwinter in the New Jersey, making them a very effective alternative to insecticide control of this pest. In fact, using the parasitoids saves New Jersey farmers more than an estimated $1.2 million annually in insecticide costs and time, and the investment from the New Jersey Soybean Board offsets insect release costs.

“This program has been successful, because I haven’t had much of a problem with Mexican bean leaf beetles, though my father says they used to be a nightmare,” says Fred Catalano, a soybean farmer from Woodstown, who currently serves as chairman of the New Jersey Soybean Board. “As farmers, we face enough adverse conditions. This checkoff investment means one less thing for us to combat. Any variable we can remove from farming – including a pest like this – is a huge plus.”

In addition to monitoring and controlling Mexican bean leaf beetles, especially during June and July, Hudson also surveys and monitors other problem soybean pests. In August, Brown Marmorated stink bugs can be a problem in New Jersey. If field scouting finds populations of this insect at economic threshold levels, farmers will be informed so they can choose to treat as appropriate.

“We are also starting to study an exotic insect already present in this region that may be a beneficial insect that can be used to control Brown Marmorated stink bugs the same way we use wasps for Mexican bean leaf beetles,” Hudson adds.

The project also includes monitoring for two invasive species, the spotted lanternfly and the kudzu bug. These insects have not yet become a major issue in New Jersey yet, but they have been seen in neighboring states. While their impact on soybean yields is not yet known, monitoring for them provides data that can guide regional university and Extension researchers as they determine economic thresholds and effective control programs.

Others interested in working with beneficials to control insects can learn more from Hudson. New Jersey’s beneficial insect laboratory is willing to work with farmers and organizations outside of their state.

Photos: Wayne Hudson

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.