Stinkbug numbers are sky high in Arkansas wheat, and Gus Lorenz isn't terribly optimistic that row crops will be able to escape the pest's eventual march over into other vegetation.
“I wish I could say otherwise, but rice, cotton and soybean growers had better get ready. If there's a front-runner for ‘Pest of the Year,’ the stinkbug would win going away right now,” says the Arkansas Extension entomologist. And while researchers have found that pyrethroids work extremely well on green stinkbugs, their brown cousins are another matter.
“If we're talking about brown stinkbugs in cotton, there are only a couple of products that do a good job: methyl parathion and Bidrin,” says Lorenz.
With its short residual, methyl parathion isn't the product of choice, says Lorenz. But everything else is being squeezed out by the government — including Bidrin.
The problem with Bidrin is the EPA is in the process of phasing it out. It's by far the most effective compound for controlling brown stinkbugs, says Lorenz. But it's also a toxic compound and, as such, has become a loader/handler issue with the EPA.
Recently, EPA issued a re-registration decision for Bidrin. It was feared that the agency would severely curtail use of Bidrin.
Instead, after much testimony from farmers, Extension specialists and industry leaders, EPA allowed Bidrin to be sprayed aerially and at current rates at least through 2004. After that, however, nothing is set in stone.
“Bidrin has been our standby product on browns and now our use is being limited. In several years, aerial applications of Bidrin will be phased out. Even if EPA simply limits Bidrin to ground application, in late July and August (when the stinkbug is most destructive) we won't be able to use it.”
Bidrin is a compound often used on aphids, thrips and plant bugs up through squaring of cotton plants, says Lorenz.
“My understanding is we'll be limited to 0.83 pound active ingredient per season. You'll get one one-third pound shot for plant bugs and one-half pound shot for stinkbug control.”
Researchers have looked at many products to replace Bidrin, says Lorenz. “We've looked at Steward, Intruder and others. But they just don't do a very good job.
“It looks like growers will be using much more methyl — that's about all that's left.
“Methyl is good on stinkbugs for a couple of days. But three or four days after spraying, you're looking at needing to spray again.”
Lorenz says stinkbugs are particularly bad around Poinsett County in northeast Arkansas and Lonoke in the central part of the state. The first week of May, Lorenz and colleagues were getting one stinkbug per sweep.
“The numbers are high, but we're not sure how damaging they are,” he said. “A study out of Louisiana says to treat when there's one stinkbug per 10 (wheat) heads. I don't know if we've reached that level yet.
“I know grain handlers are very sensitive about stinkbugs because they were around last year, too.”
Entomologists have seen high insect populations this spring — particularly arthropod populations like stinkbugs, ticks and others.
Besides cotton, Lorenz says, rice growers need to be vigilant in looking for stinkbugs in their crops.
“The potential for stinkbugs to be a major player in rice is all too obvious. Growers need to be monitoring populations from very early on because unless something interesting happens environmentally, stinkbug numbers are on a sharp upswing. So far, stinkbugs are definitely the big target this year.
“Different year, different problems. Unlike last year, this time around we've had a very light population of armyworms. For whatever reasons, they're just not out in large numbers.
“A parasitic wasp (Braconid) has been very active in controlling the armyworms. We've seen a lot of those, too.”
As a point of interest, Lorenz says Arkansas also has an overabundance of a ground beetle called the caterpillar hunter. Lorenz believes the beetles' strong emergence is a result of last year's massive true armyworm population and currently may be keeping armyworm numbers in check.
“This big beetle is a true predator and loves feeding on caterpillars. Last year, the armyworms were horrible in wheat. I think the beetles feasted, were healthy and laid a lot of eggs,” he said.
“We're now seeing an incredible number of these beetles. The last week of April, I went to a school in Marshall, Ark. Literally hundreds and thousands of these beetles were crawling all over the school.”
The beetles are big, pretty and beneficial, says Lorenz.
“They're a reflective green and are about an inch long.
“They smell terrible, though — like rotten cheese. But they're amazing insects and do a lot of good.”