What is in this article?:
- Kudzu bug has potential to change everything in soybean insect management
- Can cost growers five bushels per acre
- The kudzu bug is poised to change soybean insect management in the Southeast.
- It's expected that kudzu bugs will be present in every Alabama soybean field in 2014.
- Soybean acres have increased in Alabama in recent years.
KUDZU BUGS ARE shown on young soybeans in Auburn, Ala., this past year. The pest is expected to be found throughout the state in 2014.
If you’ve been growing soybeans the same old way year after year, things might be about to change.
“The kudzu bug — in my opinion — has the potential to change everything we’ve ever had to do in managing soybean insects,” says Auburn University Extension entomologist Tim Reed.
“It’s one of those things that make it difficult for coming up with thresholds.”
But after consulting with colleagues and others in the field, Reed has come up with what he calls a “tentative” economic threshold for treating kudzu bugs in soybeans in 2014.
“Since 2009, this insect pest has spread to eight Southeastern states, and it has spread very rapidly. Next year, I think we’ll see kudzu bugs reach economic damaging levels in even more fields unless parasites can keep up with them,” says Reed.
The Alabama Cooperative Extension System’s economic threshold for kudzu bugs in soybeans this year, he says, call for treating prior to first bloom when there is an average of five kudzu bugs per plant for the entire field.
“After first bloom through R6, apply an insecticide when a sweep-net sampling catches 10 adults per sweep or one nymph per sweep. When using a sweep net, a sweep is defined as one sweep across two rows using a 15-inch diameter sweep net.,” says Reed.
“If immature kudzu bugs are easily and repeatedly found on petioles and main stems during visual inspections of the canopy, treatment is likely warranted.”
He advises that growers should not limit all sampling to border rows where populations build initially.
“Border treatments in some cases have slowed the movement of adults across fields. If immature kudzu bugs are easily and repeatedly found on petioles and main stems during visual inspections of the canopy, treatment is likely warranted,” he says.
This threshold, he says, is based on one year’s experience and will be adjusted as more research is conducted and experience is accrued.
“Due to the tendency of this pest to congregate on the field borders, initially it is important that growers use an average population estimate for whole fields before making a whole-field insecticide application.”
During 2013, kudzu bugs continued to migrate into soybean plots at Prattville through the third week of July, adds Reed.
“Re-treatment may be necessary when a treatment is applied before migration into soybeans stops. Spraying for kudzu bugs will significantly reduce beneficial insects which could result in economic infestations of caterpillars.”
The kudzu bug, he says, has sucking mouthparts, feeding mainly on the stem and leaf petioles. It primarily will be on the main stem of the plant.
“The effects of this pest mimic drought conditions. They form lesions on the main stem and petioles, and they do feed on pods occasionally. They’ll reduce the number of pods per plant, the seeds per pod, and the seed size. They’ll make the plants shorter if they get on them when the plants are small.”
The immature stage is flat, hairy and fuzzy and looks like nothing else, says Reed. A high percentage of the over-wintering females are already fertilized when they move into kudzu and soybeans.
“I’ve seen them on kudzu at the Atlanta airport during the first week in March. You will see this pest in all soybean fields in the state in the not-too-distant future. They’re better at over-wintering and surviving harsh winters than the boll weevil.”
The problem is if growers start spraying for kudzu bugs early, they’ll end up having to spray for them three or four times, he adds. “When they’re bad, they’re bad. We don’t want kudzu bugs to cause us an economic loss.”
Many specialists in other states won’t have an adult threshold at all, says Reed. “If immature kudzu bugs are easily found on petiole and main stems during visual inspections of the canopy, the treatment is likely warranted. They’ll mainly start at the border rows and then move across the fields. Border treatments in some cases have slowed the movement of adults across the field.”