What is in this article?:
• The one good thing that can be said about the kudzu bug is that it usually doesn’t feed on pods — it’s primarily a stem feeder.
• The type of yield loss depends on when the bugs put enough stress on the plant to cause yield loss.
• It can be a very serious pest if left uncontrolled.
THE KUDZU BUG is a relatively new insect pest in Southeast soybeans, but it can cause significant yield reductions if not treated.
Widespread in three years
“In three years, it has spread over a large area, and we’ve actually got a couple of sites in Mississippi where the bug probably hitchhiked in on some type of vehicle.”
It appears, says Roberts, there are two generations of kudzu bug each year. The insects over-winter as adults, and they can be found in loose leaf litter and other protective areas on the ground. They also can be found in tree bark.
“Two generations per year is a long life cycle,” says Roberts.
“From eggs to adults is about six to eight weeks. The cooler the temperature, the longer it takes to get to the adult stage.
“Adults also live for a long time, meaning once they’re in soybean fields, they will be there for awhile. We typically see higher infestations at the edges of fields. So when you’re making treatment decisions, don’t base the entire field on what you see in the first 10 feet.”
As its name implies, the kudzu bug likes kudzu, he says.
“So kudzu is a very important part of the picture when we consider managing the pest in soybeans. We know a lot of these insects are produced in kudzu patches. Ultimately, those insects will move to soybeans in the latter part of June and into July. A lot of these bugs originate in a kudzu patch.”
This past year, he says, over-wintered bugs were seen moving directly to soybeans and not stopping in kudzu.
“If we plant in April, for example, we may see kudzu bugs come directly from over-wintering. That may not be important to us in Georgia, but it could be important in terms of where this insect will go in the United States. We may not need to have kudzu for this insect to be established.”
In 2012, says Roberts, it was confirmed that early-planted soybeans are at much higher risk to kudzu bugs than later planted soybeans.
“We planted a Group V and a Group VII soybean in Tifton in April, May, June and July. A kudzu bug egg mass usually will contain from 15 to 20 eggs. We counted the number of egg masses on five plants, when the soybeans reached the R2 stage, about 60 days after planting.
“Our early beans had many more egg masses on them at R2 compared to May, so expect more pressure the earlier you plant.”
The yields of treated and untreated soybeans were compared at various planting dates, he says.
“We treated with Indigo from Syngenta. We weren’t trying to treat these beans economically — we treated every two to three weeks to keep them as clean as possible.
“With our early planting date, we had 76-percent yield loss, and it might as well have been 100 percent. There just wasn’t much there.
“In May, we lost 54 percent, and the difference between the untreated and treated continued to get smaller as the planting date became later.