Early planted soybeans are progressing and looking good. Some varieties are drying down and some have already been harvested. These soybeans are progressing at R6 (Full Seed)growth stage now. R6 is defined as the beans inside the pod are touching. We’ve had some questions about stink bugs this week. Stink bugs, corn earworms and fall armyworms are recognized as soybean pod feeders. I ran a sweep net through a few fields on a plantation yesterday and the highest number I found was 5 per 25 sweeps, which is below threshold. Above is a brown stink bug adult in the field. Below is a green stink bug nymph. This is probably one instar from being an adult. Southern Green Stink Bug nymphs usually have pink/reddish markings on them.
Our decision to spray for stink bugs is determined by thresholds. You can use either a drop cloth and shake plants over the row to count insects by row foot or use a sweep net. When the soybeans are this far along, I like using a sweep net. Below are thresholds in the 2014 UGA Soybean Production Guide from UGA Extension Entomologist Dr. Phillip Roberts:
- Bloom to mid pod fill – 0.33 stink bugs per row foot or 3 per 25 sweeps.
- Mid pod fill to maturity – 1 stink bug per row foot or 6 per 25 sweeps.
*beans being grown for seed production, 1 stink bug per 6 row feet will justify control.
- Should be controlled at any time after bloom when an average of 2 per row foot (1/2 inch or longer) are found.
Since the beans are at R6, we still need to treat for pod feeders if thresholds justify. Once we hit R7 (Beginning Maturity), we no longer need to treat for insects. R7 is determined when at least one pod can be found on the plant which is mature or brown/tan in color. Pods and leaves start to “yellow” during this stage. This field is not there yet.