Research Highlights

Preventing Mexican Bean Beetle Outbreaks

By Laura Temple

Today, few New Jersey soybean farmers remember how Mexican bean beetles devastated crops more than 35 years ago. Outbreaks of this leaf-eating species of ladybird beetle were common through the 1980s, when infestations of larvae would devour leaf tissue in soybean fields, leaving just a lacy skeleton behind.

Thanks to an ongoing checkoff investment from the New Jersey Soybean Board, the New Jersey Department of Agriculture uses beneficial insects to prevent outbreaks. Wayne Hudson, an entomologist for the Phillip Alampi Beneficial Insect Laboratory within that department, leads an annual program to manage Mexican bean beetles in soybean fields. 

His team monitors soybean fields in central and southern New Jersey for Mexican bean beetles. When larvae populations reach the treatment threshold, they release a beneficial parasitic wasp called Pediobis fovelolatus, native to India. 

“We start scouting fields in June, and continue monitoring them through August,” Hudson explains. “We usually start releasing wasps at the end of June.”

The wasps lay eggs inside Mexican bean beetle larvae. When those eggs hatch, the wasp larvae feed inside the bean beetle larvae, dramatically reducing the population of pests feeding on soybean leaves. The parasitic wasps have proven to be an effective alternative to insecticides, saving New Jersey farmers more than an estimated $1.2 million each year in inputs and time. The wasps cannot survive New Jersey winters, but the New Jersey Soybean Board offsets annual wasp release costs.

“This program has been successful for years, but its value has increased with the increase in organic farms in New Jersey,” Hudson says. “Because organic farmers have limited options for insect control, pest populations can build and spread. Our biological control program keeps Mexican bean beetle populations down in all fields, without relying on insecticides.”

In 2022, 28 farmers participated in the program, allowing his team to monitor about 50 soybean fields for Mexican bean beetles and release wasps in those fields. Research shows that one wasp release can protect crops in a 5-mile radius, providing reliable pest coverage for the whole region. 

While watching Mexican bean beetle populations, Hudson and his team also pay attention to other invasive or problem insects for soybeans.

“Fortunately, kudzu bugs are not advancing, and the invasive spotted lantern fly is not damaging soybean fields,” he says. “Populations of brown marmorated stink bugs have been down, and if we see green stink bugs, mites or other pests, we let the cooperating farmers know as a courtesy. We serve as an extra set of eyes for them in the field.”

Published: Jul 10, 2023