David Owens, Extension Entomologist, owensd@udel.edu
Sorghum
Continue scouting late sorghum for earworm and sugarcane aphid. Sugarcane aphid activity is high right now and a little bit earlier than last year. Fortunately, our September is forecast to be much cooler than last year’s and soil moisture will help the plants tolerate more aphids than last year. There are two thresholds used for sugarcane aphid: 40 – 100 per leaf or 30% infested plants with localized areas of honeydew present. I only recommend Transform or Sivanto for sugarcane aphid. Sivanto can be applied at sub-label rates and still achieve excellent control.
Soybean
Continue scouting for corn earworm and stink bugs. Stink bug thresholds are 5 bugs per 15 sweeps. Thresholds for seed production or for edible soybean are half that of grain. Some double crop fields in a widely scattered area around Sussex and southern Kent had threshold levels of worms show up late last week. Most are still small, but a sizeable proportion are approaching medium size. Scout your double crop fields. If you have worms, they will be getting harder to control soon. While scouting for worms, take note of defoliation. R5 defoliation threshold is 15%. Green cloverworm activity took a hit recently due to diseases in the worms, but in some fields they are still abundant. Soybean looper continues to be active in fields, though I have not heard of any fields with large populations. Diamides are somewhat inconsistent with soybean looper. If you have both earworm and a few looper, products like Prevathon or Besiege may do well.