Over the past 7 days we have seen and heard reports of high (60-100 per 5 row feet) infestations of velvetbean caterpillars (VBC) and soybean loopers (SBL) in fields across much of the southern portion of the state. The VBC (4 prolegs) can be pretty easily managed with pyrethroids while SBL (2 prolegs) require products like Prevathon, Besiege or Intrepid Edge.
Management decisions should be made based on the primary caterpillar species found in fields and based on current defoliation estimates. Our threshold from R1-R6 is 20% defoliation. We can back off to 30% from R6-6.5 (R6 +7-10 days) and can terminate applications after that point.
We have also seen and heard reports of redbanded stink bugs (RBSB) from the Mississippi border to Montgomery and south to the ocean. This pest poses a major threat to our soybeans and is one we need to scout for in fields from R5 – R7. The RBSB can do more damage and damage more mature beans than our traditional stink bugs (green, brown, southern green).
Our thresholds are 4 RBSB per 25 sweeps or 1 RBSB per 5 row feet. We can back off to 10 RBSB per 25 sweeps from R6.5 – R7 and terminate sprays if conditions are conducive for the beans to dry down.
Current recommended thresholds, insecticides and rates can be found in the Alabama Soybean IPM Guide. The soybean insect pest portion of the 2020 Cotton and Soybean Scouting School can be found below.