Growers in the Midsouth are more conscious about making sure fields are scouted for damaging insects. After quick-striking invasions of stinkbugs forced some to plow up what would have been 60-bu. soybeans, scouting for the pod-hungry critters has become a necessity.
Alvin and Jerry Ford, who farmed for years near Lake Village, AR, were among those who learned about stinkbugs the hard way.
“They were completely unknown in our area until about 2000,” says Jerry Ford, a member of the Arkansas Soybean Promotion Board and the United Soybean Board. “That year, the infestation of our Group Vs was so bad that we weren't able to harvest them.”
The Fords now lease their land to others, but still keep track of stinkbugs and other insect populations in the soybean- and cotton-producing region.
The brown stinkbug, green stinkbug and the southern green stinkbug are the pests in question. The browns are the most prominent of these pod feeders.
Stinkbug eggs are distinctively laid on the leaves of soybeans in clusters in tight rows. Individual eggs are barrel-shaped. The adult bugs are about the size of a small corn kernel. The brown version has rounded shoulders.
Larger seed crops like soybeans and cotton are a delicacy for them, so control measures are essential if trouble populations are found. Chris Tingle, University of Arkansas soybean specialist, says that when scouting for stinkbugs, look for at least one bug/ft./row in 38-in. rows. (In cotton, it's one bug/6 ft./row on 38-in. rows.)
Methyl parathion was among the insecticides that showed the best control results in Arkansas tests.
On the Fords' land, Group IV beans are planted about April 1 through April 20. Group Vs are then planted.
“Growers here like to go with the earlier varieties to take advantage of early-season rains and to relieve the need for irrigation,” says Jerry.
In 2000, the Fords went from cotton to soybeans on one particular field. A stinkbug invasion took place virtually overnight. Before they knew it, the Fords and other area growers faced a mass of stinkbugs that destroyed much of the crop.
There was no positive proof, but the Fords felt the region's initial boll weevil eradication program for cotton helped promote the stinkbug infestations because of possible beneficial insect kills.
“No one really scouted for stinkbugs that year,” says Alvin, noting that the infestations hit in late July and early August. “They caught us all by surprise.”
Tingle says that while adult stinkbug damage can continue through late summer and early fall, research has shown that soybeans are susceptible to stinkbug feeding damage in early growth stages.
Soybeans should be closely monitored for pod feeding insects through the R7 growth stage, where one normal pod on the main stem has reached its mature pod color.
“Soybeans well into seed fill are still susceptible to feeding from insects such as stinkbugs,” says Tingle.
Arkansas insecticide tests showed that most other pyrethroids are effective in controlling stinkbugs. The strongest control of green and brown stinkbugs was seen from Methyl parathion and Penncap-M. Asana XL, Fury, Karate, Baythroid, Lannate 2.4LV and Mustang Max also showed good performance.