GRASS STRAIN FALL ARMYWORM        mdashPhoto by Scott Akin

GRASS STRAIN FALL ARMYWORM —Photo by Scott Akin

‘Armywormageddon’ broke out in Arkansas soybeans this year

Stink bugs, armyworms, bollworms, and the rapidly proliferating kudzu bugs — all can pose challenges for southern soybean producers.

New potential soybean insect problems include the red-banded stink bug, the brown marmorated stink bug, and the grass strain of the fall armyworm.

Southeast, Mid-South and Southwest entomologists offer tips on how to stay on top of these and other soybean insect pests.

The red-banded stink bug, which comes out of the Caribbean, is a tropical species that likes heat, so a cold winter like Louisiana experienced in 2013-2014 could hold back populations in 2015.

“Our research shows red-banded stink bugs don’t survive well at temperatures below 15 degrees F,” says Louisiana State University Entomologist Jeff Davis, Baton Rouge. 

“It’s an aggressive species that reproduces quickly, and is more difficult to control than our other stink bug species, such as green stink bugs and southern green stink bugs.

“The pest reproduces well in clover, so watch any clover areas around your fields or roadsides, because red-banded stink bug populations could blow up in those areas after a warm winter.”

Bollworms top yield robber

Bollworms rank as the No. 1 insect pest in Arkansas soybeans — hands down.

“Bollworms cause us more yield loss than any other pest,” says Gus Lorenz, Extension IPM specialist, Lonoke, Ark. “They especially appear in thin-stand broadcast beans and row beans that haven’t lapped.

“I urge growers to scout every field. Don’t assume you’re safe just because the middles have lapped. I also encourage the use of newer products like Belt, Prevathon, Besiege or Intrepid Edge for bollworm control.

“Stink bugs would be our next biggest insect problem every year. After that, depending on the year, different insects can be problematic, such as fall armyworms, which were a huge pest in small beans in 2014. It was an ‘Armywormageddon.’” 

Stink bugs are definitely the No. 1 group of insect pests for South Carolina soybean growers. Corn earworms are No. 2, followed closely by soybean loopers.

“We can also have problems with tobacco budworms,” says Jeremy Greene, Clemson University entomologist, Blackville.

Build up in peanuts

“The tobacco budworm seems to be more prevalent in recent years, probably due to the Southeast’s peanut acreage. They can build up in peanuts and produce a subsequent generation that infests later-planted soybeans. 

“In addition to stink bugs, Heliothines, and loopers as our three regular pests, we can have occasional problems with other insect pests. For example, we can have problems with the velvetbean caterpillar in the southern part of the state.

“Additionally, we’ve selected for kudzu bugs that are cold-tolerant because of the frigid 2013-2014 winter, so I expect they will be more pronounced in the future.”

The three top economic pests that Mississippi soybean growers confront every year are soybean loopers, stink bugs and bollworms. Their order of importance varies year-to-year and field-to-field.

“The introduction of diamide chemistry was a game changer in caterpillar pest control,” says Angus Catchot, Mississippi State University Extension entomologist, Starkville. “The residual is much longer than that of older chemistry.

“Depending on the year, red-banded stink bugs, which have been a horrible problem in Louisiana, have made their way up here a couple of years. It’s a much harder pest to deal with, but seems to be sensitive to cold weather. So after a hard winter, it takes a good year or two for them to blow back up.”

Watching in 2015

“The kudzu bug has appeared almost in every county in our state,” Catchot says. “Fortunately, we didn’t see the big blowups in 2014 we were expecting, but the pest did hit threshold levels in a few fields. We’ll watch it in 2015.”

Alabama soybean growers need to watch out for a new pest — the brown marmorated stink bug.

“In 2014, we found this pest in soybeans at the Prattville Experiment Station, as well as in six other counties,” says Tim Reed, Extension entomologist, Belle Mina. “It’s moving south from the states above us. It’s a pretty serious pest in northern Virginia.

“We also need to keep an eye on the kudzu bug, which has the potential to become a serious, widespread, economic pest in our state. Although there were some high numbers in spots, their numbers were down overall in 2014, possibly because of the extremely cold winter.

“Three-cornered alfalfa hoppers continue to be an issue on seedling soybeans in some parts of the state. For control, growers often add an insecticide with their early herbicide application on seedling soybeans.

Insects on wheat beans

“Additionally,” Reed says, “we generally have an insect complex during the reproductive stage of soybeans planted behind wheat. At sub-threshold levels, growers might want to hold off automatically adding an insecticide to their fungicide, which might exacerbate caterpillar problems later.

“Finally, make sure stink bugs don’t sneak up in wheat beans. They can cause a lot of damage, especially when beans are first trying to fill out. The grass strain of the fall armyworm was a scattered problem in wheat beans in 2014. I know of at least 6,000 acres that were treated.”

What happened to all the kudzu bugs in 2014?

Their numbers in Georgia were down by approximately 80 percent, compared to previous years.

“Nobody really knows for sure what happened,” says Phillip Roberts, Extension entomologist, Tifton. “Could be the population is getting in balance; could be due to the cold temperatures in the winter and spring of 2014; could be natural control by an egg parasitoid discovered in 2013 also impacted kudzu bug populations. 

Continue scouting

“Regardless, in 2015, we need to continue scouting for kudzu bugs, especially in early-planted soybeans, and treat at a threshold of one immature kudzu bug per sweep.    

“Stink bugs remain Georgia’s No. 1 soybean insect pest. We also deal with soybean loopers, velvetbean caterpillars and lesser corn stalk borers. We were hot and dry in 2014, and had late season outbreaks of the lesser corn stalk borer.”

Stink bugs are the top insect problem Tennessee soybean growers combat yearly. Other major problems include pod feeding and defoliating caterpillars, including corn earworms and soybean loopers.

“Fortunately, the kudzu bug hasn’t spread as quickly as we thought it would,” says Scott Stewart, Extension entomologist, Jackson. “Winter temperatures knocked it back for 2014. But I expect it to be more of a problem in West Tennessee in 2015.

“The kudzu bug is not difficult to control with products containing bifenthrin, such as Brigade. Other pyrethroids like Karate and Mustang Max also work.

“The key is timely application,” Stewart says. “Kudzu bugs will migrate into the crop for several weeks, and it takes a high population to cause crop injury.

“So, key your application on when you start to see immatures in the sweep net. Most states use a threshold of one immature per sweep. One spray normally takes them out.”

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