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Kudzu bug making inroads in Southeast soybeans

Kudzu bug making inroads in Southeast soybeans

• The kudzu bug is a new insect pest that has invaded the Southeast and is probing the Mid-South. • Researchers observed a 19 percent average yield loss in Georgia trials in 2010, and even greater losses in 2011. In five trials yield loss ranged from 22 percent to 47 percent. • Growers definitely need to scout for the kudzu bug and treat if necessary.  

For the 2012 insect outlook, southern soybean growers can expect a new kid on the block — the kudzu bug — as well as the usual suspects.

Several Southeast and Mid-South university entomologists discuss potential insect problems, and what growers can do about them.

The kudzu bug is a new insect pest that has invaded the Southeast and is probing the Mid-South.

“In the fall of 2009, the kudzu bug was first found in the U.S. in nine northeast Georgia counties,” says Phillip Roberts, Extension entomologist, Tifton, Ga. “Today, it’s in 120 counties of Georgia, all of South Carolina, 50 North Carolina counties, one Virginia county, and five Alabama counties.

“We observed a 19 percent average yield loss in Georgia trials in 2010, and even greater losses in 2011. We harvested five trials and our yield loss ranged from 22 percent to 47 percent.

“Growers definitely need to scout for the kudzu bug and treat if necessary. We’re still developing workable thresholds; we suggest treatment when you find three to five bugs per plant.”

While Georgia researches ways to control the new pest, the state still contends with its regular insect problems. The state’s primary pests are pod feeders, mainly stink bugs.

“We also have a complex of foliage feeders, with the velvetbean caterpillar and soybean looper being the primary ones,” Roberts says. “We’ve also had some tough situations with lesser corn stalk borer, which is a sporadic pest for us.”

In 2010, the kudzu bug was found in 16 out of 46 South Carolina counties. Its population exploded and completely covered the state in 2011.

Jeremy Greene, Clemson University entomologist, Blackville, S.C., says, “Depending on factors such as planting date, maturity group, and others we are just beginning to learn about, yield losses from this insect range from zero  to 50 percent loss if not controlled.

“We’re still researching cultural methods to control this pest. The kudzu bug responds well to insecticides, but it’s not listed on any insecticide label. We can still legally, but carefully, make recommendations to producers for using insecticides already labeled in soybeans, but we will have to work with the chemical companies to get this pest added to their labels and recommended in ways that will provide good control.

“We have generated some data, but need to initiate more trials, showing which products are efficacious on this insect. We have only had 2011 to do any appreciable field research on this species. We are currently planning for significant research next year.”

South Carolina outlook

South Carolina growers can also their normal insect problems in 2012, Greene says. “Although we didn’t have widespread problems with stink bugs in 2011, they are still perennial pests that we deal with in soybeans. We also have sporadic problems with corn earworms in some areas, as well as defoliating insects including the velvetbean caterpillar and the soybean looper.”

(Additional information on the kudzu bug in South Carolina can be found at Background on the pest can be found here).

In Arkansas, as well as other Mid-South states, the corn earworm has been the biggest soybean insect pest for the last two years.

“Of all the insect pests, it is the single biggest insect threat to soybean yields,” says Gus Lorenz, Arkansas Extension IPM specialist, Lonoke.

“We had extremely high numbers in 2010 and they were even higher in 2011. We saw early problems behind pyrethroid applications, so we began tank mixing with Orthene and other materials. We also used a new Bayer chemistry, Belt, which worked extremely well.

“Our big bollworm problems in 2011 were a result of flooding in the spring. Growers can help themselves by planting early whenever weather permits. Early planted beans often will avoid these bollworm populations.”

Additionally, fields not lapped at bloom were the ones that were most severely affected bybollworms.

“For some reason, most Lepidoptera pestsare attracted to open canopy beans, particularly with the bollworm, but also with the armyworm complex; even loopers are worse in beans with an open canopy,” Lorenz says.

“So, anything growers can do to achieve canopy closure prior to bloom will be helpful. That includes planting early, and maybe closing up rows.”

Mississippi’s production practices of planting more corn, more Group V beans, and more wheat beans mean that the state’s soybean growers will continue to have problems with corn earworms and loopers, says Angus Catchot, Extension entomologist at Mississippi State University.

“We plant a large portion of our soybeans late so we can manage the harvest of all of our different grain crops,” he says. “As long as we continue to do that, we’ll have problems with corn earworms and loopers, which will be our No. 1 and No. 2 pests, respectively, going into 2012.

“The impact of these pests can be minimized by planting early and avoiding mid-May planted beans. But we can’t plant our entire crop early, so we have to manage it by scouting and spraying when economic thresholds are reached.

Saw earworm failures

“Last year we saw pyrethroid failures against corn earworm. But we extensively used a Bayer product, Belt, and it was very efficacious on the pest. It also offers long residual control against loopers.

“We’ll also continue to watch stink bugs, even though for the last two years they really have been a non-factor. They have  traditionally been our No. 1 pest, but our winters have beaten them back.”

Catchot says Bt soybeans might one day be another tool for soybean growers. “It’s something that we and several companies are researching,” he says. “It’s a potential tool, but there are many issues that have to be talked through from a resistance management standpoint since we already grow Bt corn and Bt cotton.”

Based on an insect pest survey conducted by Extension personnel, Alabama’s most abundant soybean insect pest in 2011 was the three-cornered alfalfa hopper (3CAH), which can cause economic loss even in late season beans.

“You want to treat only when the economic threshold is reached, because an application will take out beneficials and open you up to a worm problem,” says Tim Reed, Alabama Extension entomologist, Belle Mina.

“Based on one study we conducted in 2010, three per sweep — sweeping across two rows — is a treatable level once soybeans reach the R5 stage. We don’t have data on the yield response of soybeans when abundant numbers of 3CAH are treated in the R6 stage.”

Another control option is a seed treatment. “Growers especially need to look at seed treatments if they’re planting soybeans behind wheat and they’re not planning an early season insecticide application,” Reed says.

“Scouting for three-cornered alfalfa hoppers is difficult when beans are just two to three inches tall. So, either use a seed treatment or make an automatic spray when beans are small, if you want to reduce 3CAH damage to young soybeans. The seed treatment also helps in controlling bean leaf beetles.

“Overall, we had light stink bug pressure in 2011, but stink bug numbers increased late in the season when beans were less susceptible to a yield reduction. If we have a mild winter, we might see stink bug pressure pick up in 2012.

“Although three new stink bug pest species were first identified in Alabama in 2010, our survey in 2011 did not detect the red-shouldered or brown marmorated stink bug in soybeans. One red-banded stink bug was found in soybeans in Baldwin County in extreme southwest Alabama in 2011. This pest was also found in soybeans in the same area in 2010 in higher numbers.

“We also sprayed for some soybean loopers in extreme southwest Alabama when the numbers began building in August. We didn’t see a lot of soybean podworm problems. We’re also keeping an eye out for the kudzu bug, which has been found in five Alabama counties on kudzu — but not in soybeans to date.”

Stink bugs, particularly the green stink bug, but also the brown stink bug, are the pest that Tennessee soybean growers are most likely to have to control. Additionally, for the last couple of years, particularly in the Mississippi River bottoms, growers had a significant issue with corn earworms.

“That was definitely our No. 1 pest in 2011,” says Scott Stewart, Extension entomologist, Jackson, Tenn.

“We can do several things to alleviate many insect problems. The first is to plant relatively early-maturing varieties. The Mississippi River often floods, and after the waters recede we plant our Group IVs and Vs. But since they’re planted later than normal, they flower later in the year and they’re set up for both corn earworms and soybean loopers.

“When possible, try to plant in our recommended planting window and avoid planting in late June and July, which gets us in trouble.”

n addition to planting early, Stewart urges growers to use insecticide seed treatments on some of their early planted soybeans.

“Our data show we usually get higher yields when we plant early, and we also get more benefit from insecticide seed treatments. If I were planting early, particularly in no-till situations, from April through most of May, I would use a seed treatment.”

Louisiana’s main insect problems are stink bugs and foliage feeding caterpillars. Early planting always help with the foliage feeders and to some degree with stink bugs, depending on the overwintered populations and how fast they build up.

“We had an unusually high corn earworm year in 2011,” says Jack Baldwin, Louisiana State University Extension entomologist, Baton Rouge. “Just be on alert, particularly when beans start blooming.

“Other than that, it’s just a matter of scouting, spraying, and knowing which pest is in the field and at what levels. If you have a combination of pests, use a product that controls most, if not all, of them, or tank mix another material to take care of the problems — with one application, if possible.”


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