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.
Worse in early-planted beans
“I’m not trying to say we need to plant soybeans late to manage kudzu bugs. You need to plant soybeans when you have the greatest yield potential. But expect kudzu bugs if you plant early.
“Also at Midville, our greatest yield loss came in the earliest planted soybeans.”
Roberts also observed kudzu bugs feeding on seedling soybeans, in the earliest plantings.
“Where we had bugs on seedling soybeans — and we tried to get an infestation of about 10 adults per plant — we did see a reduction in plant height, so they are impacting seedlings. But I think that will be a rare occurrence on the farm.
Roberts notes that the kudzu bug is not a difficult insect pest to kill, and that using a sweep net is a good way to monitor the insect in soybeans.
Data from 27 trials in Georgia, South Carolina and North Carolina has been summarized in which several different compounds were used to treat kudzu bugs, he says. Some of the treatment gave better than 80 percent control.
Multiple classes of insecticides have shown activity on kudzu bugs. Insecticide treatments containing bifenthrin, cyhalothrin, zetacypermethrin, carbaryl or acephate provided greater than 80 percent control two to five days after treatment in insecticide efficacy.
Growers actively treating kudzu bugs with broad spectrum insecticides should consider using a preventive application of Dimilin at the R2/R3 growth stage for control of velvetbean caterpillar and green clover worm.
Knowing when to spray is still the primary question to ask when treating for kudzu bugs, says Roberts.
“Over the last two years, we’ve compared a lot of different thresholds or triggers. Looking at yields from our trials, as long as you spray kudzu bugs at some point, yield is about the same.
“We had two threshold verification trials in Tifton. We settled on a threshold of one immature kudzu bug per sweep. Our threshold called for only a single spray, and there was a difference in yields with just that one spray.”
If you have a problem with this insect pest, you need to address it or it can hurt you, says Roberts. “But we have noticed we can get good control with a single spray. I’m not ready to say we can do it every time, but we’ve done it over the last three years.”
A sweep net can provide you a lot of valuable information for kudzu bugs and other pests, he says.
You can also scout with visual observation, but you need to trigger any treatment with the immatures.
“If you can find immatures easily, then a spray is definitely needed. A lot of times we don’t see this migration back into the field after we clean it up.”
If you have early maturing beans — Group V and Group VII on the same farm — when the Group V beans dry down, the bugs could leave those and jump to the Group VII, he says.
“You’re never really out of the woods with kudzu bugs, but if you use the recommended threshold, you can usually get them with a single spray.”
Soybeans need to be protected from kudzu bugs at least to the R7 stage, says Roberts.
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