That’s the mid-season report by Penn State entomologist Dr. John Tooker, who heads the Soybean Sentinel Plot program, sponsored by the Pennsylvania Soybean Board. The goal of the program is to track insect and disease pest populations in typical soybean fields around the state and share this information with growers.
Thirteen extension educators from throughout Pennsylvania are tracking populations in 22 fields in 19 counties. Fields used in the project were established in May to mid-June and scouting began upon emergence. Reporting pest populations are reported weekly in the Penn State Field Crop News during the growing season.
Tooker reports that as of the beginning of August, “The main pest remains Japanese beetles, but none of the damage found in our plots approach the levels of defoliation that should cause growers to protect their fields with an insecticide. It’s good to remember that soybeans can withstand 30-percent defoliation during vegetative stages without losing yield; 15-percent defoliation for bloom to pod-fill; and 25-percent pod-fill to maturity. If you apply these numbers, assess defoliation on the canopy of the field as a whole, and do not worry about isolated plants.”
This is the fourth consecutive year for the Soybean Sentinel Plot program. “Thus far and as in past years, our scouting efforts have discovered a fairly narrow range of insects and only a few diseases, but importantly, none of the pest populations have yet exceeded economic thresholds, so none of the fields so far have required pesticide treatments. This was also the case the last three years, and this is an important message for growers to hear: pest populations are not pervasive and always threatening soybean yield. In fact, in many locations and in most years, pest populations do not develop and thus pesticide use should provide no advantage,” says Tooker. “Growers should scout their own fields to understand their local pest populations and apply economic thresholds to determine whether potentially damaging insect or pathogen populations are present.”