Late season soybean insects such as stink bugs and velvetbean caterpillars bear watching this season, says Jay Chapin, Clemson University small grains specialist.
“From late August on, the major insect threats to soybeans are stink bugs and velvetbean caterpillars,” Chapin says. Stink bugs have the greatest potential because they feed directly on pods.
The treatment threshold for stink bugs is one per row foot on a ground cloth or two per 10 sweeps with a net.
Chapin says stink bug control used to be an easy call: Treat with one-half pound methyl parathion, and in high risk velvetbean areas from Orangeburg County south, add 2 ounces of Dimilin for residual velvetbean caterpillar control.
“With methyl parathion now being less available and more costly, pyrethroids are about the only option for stink bugs,” Chapin says.
Karate and Scout have some residual activity against velvetbean caterpillar, but they don't last as long as the older permethrin products such as Ambush and Pounce. “I would add 1 to 2 ounces of Dimilin to Karate or Scout stink bug treatments in high-risk velvetbean caterpillar areas,” Chapin wrote to Clemson University Extension agents in late August. “Based on what we've seen so far, we anticipate significant velvetbean populations this year.”
Soybean looper is another late-season pest usually associated with rank-growing soybeans near cotton. “Unfortunately, we do not have much rank soybean growth this year,” Chapin says.
Still, if loopers reach eight per row feet, they can be controlled with Tracer or Steward. Neither product controls stink bugs, Chapin says. “Tracer is a better choice in the southern half of the state because it has some residual activity on velvetbean caterpillars.”
Because loopers are resistant to other soybean insecticides, Chapin recommends being absolutely sure you are dealing with loopers before treating. Small velvetbean caterpillars and green clover-worms can also “loop.”