We keep hearing reports of velvetbean caterpillar (VBC) in parts of north Alabama, in particular the Sand Mountain region. This pest isn’t difficult to control but can cause serious damage. We wrote about identification last week. Remember that as soybeans can tolerate up to 20% defoliation from R1-R6 without yield loss. From R6-6.5 (R6 + ≈7 days) we can relax the threshold to 30% and terminate insecticide applications after R6.5. Unlike soybean looper, VBC can be managed with most labelled insecticides
We also need to be scouting late beans for the stink bug complex. This includes our traditional species, green stink bug, southern green stink bug and brown stink bug, as well as the invasive brown marmorated (BMSB) and redbanded stink bugs (RBSB).
For the traditionals and BMSB, treat when 8 SBs per 25 sweeps or 3 per 3 row feet. The threshold can be doubled at R6 (=16/25 sweeps) and applications can be terminated 7-10 after R6 (R6.5).
The damage potential from RBSB is more significant than the other species, thus our threshold is lower. For RBSB, treat when 4 RBSB per 25 sweeps or 1 per 3 row feet. From R6.5-R7 we relax the threshold to 10 per 25 sweeps. Under normal drying conditions insecticide applications for RBSB can be terminated at R7. However, if conditions do not allow for normal drying conditions, we still have the potential to have reduced yields and poor seed quality.
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 on YouTube.