Insects plague late-planted soybeans in Arkansas
Sep 26, 2006 8:16 AM,
By Lamar James
University of Arkansas
Extremely high numbers of stink bugs are being found in late-planted soybeans in southeast Arkansas, said Gus Lorenz, Arkansas Extension entomologist.
LORENZ
“We’re seeing fields with stink bug numbers as high as 12 times the recommended treatment threshold,” he said. “They’ve been building all year, moving from early-season soybeans to mid-season soybeans and now to late-season beans. Their numbers have magnified each time they move as they became more concentrated in fewer fields.”
Meanwhile loopers have become another serious problem for soybeans across the state. Farmers need to be scouting closely, Lorenz advised. If fields are still green, look for stink bugs and loopers and check Arkansas Extension’s MP 144 publication for threshold levels and treat accordingly, he said.
“You’ve got to get into the fields and look around. If you see looper damage in the top of the plant, it’s too late because they feed on the leaves at the bottom of the plant and move up.”
Loopers are voracious feeders and can quickly defoliate a crop.
Lorenz said it’s the end of season and farmers have spent a lot of money on fertilization and irrigation. “The last thing they should want to do is give it back to the insects.
“With the numbers as high as they are, producers are going to see some serious losses if they don’t treat. It’s not wise to save an $8 to $10 application to lose as much as 20 percent of your yield. You can’t afford not to spray.”
Don Plunkett, Jefferson County Extension staff chair, said if farmers find loopers and 25 percent defoliation in their soybeans, they should treat. Stink bugs and looper numbers can be determined by using either a shake sheet or sweep net to capture them.
Plunkett said it’s important to know whether you have soybean loopers or cabbage loopers. “The cabbage looper is easier to kill than the soybean looper. As a rule, the true legs on a soybean looper are black, but not for a cabbage looper. You have to know if you’ve got both kinds or just one kind to determine what treatment you use.
“If you’re not careful you could end up with soybean loopers still out there feeding. This time of year it’s usually best to assume that you have both species.”
Green stink bugs are easy to kill, Plunkett said, but brown stink bugs are a different story. The standard treatment this year is a pyrethroid for green stinkbugs. Methyl parathion kills both kinds of stink bugs, as does acephate. Acephate also takes care of both types of loopers. Intrepid is also useful for loopers.
A stink bug damages a soybean in the pod by injecting it with a toxin that makes it easier for them to suck the juices out. It also reduces bean quality and yield.
Plunkett stressed that farmers need to be in late-planted soybean fields scouting for insects.
“Their attention is focused on harvesting rice, corn and soybeans,” he said. “They don’t want to look because they’re tired of spending money on the crop, but a lot of late-planted beans may have high yield potential if they’re on irrigated ground. Farmers don’t want to lose that potential this late in the game.”
For more information about insects and treatment, contact your county Extension agent or visit http://www.uaex.edu/Other_Areas/publications/HTML/MP-144.asp.
