David Owens, Extension Entomologist, owensd@udel.edu
Corn
Scattered grasshopper populations have been reported and observed around field edges in corn. Western states use a threshold of 5 to 8 grasshoppers per square yard through R2. If using a pyrethroid, use the highest label rate. Recent UD spray trials have had inconsistent results using lower or mid label rates on grasshoppers in soybean. Other labeled materials include carbaryl, dimethoate, indoxacarb (Steward), Besiege, Elevest, and Vantacor. Of note, both Elevest and Vantacor have a label stipulation to include methylated seed oil for grasshopper control.
Soybean
Dectes are active in fields. If you see many in sweep samples, prioritize that field for as early and timely a harvest as possible.
Stink bugs are the most active, significant pest. Thresholds are 5 bugs per 15 sweeps. R4 and R5 are the most susceptible to yield loss from stink bugs. Green stink bugs are susceptible to pyrethroids, brown stink bugs are much less susceptible, and brown marmorated stink bugs are most susceptible to bifenthrin.
Defoliation thresholds are around 10-15% defoliation in the reproductive stages. It can be difficult to estimate defoliation accurately. One needs to look at the entire canopy. Defoliation in the upper canopy can be compensated for with increased light penetration in the lower canopy.
Spotted Lanternfly Quarantine
DDA has expanded the spotted lanternfly quarantine to the entire state. When moving equipment, plant material, packing material, firewood and any other equipment or supplies not stored indoors, check before leaving the state that no lanternflies are hitching a ride on it. At this time of the year they will be black with white spots or red with black and white spots. You can find more information about the quarantine and permitting from DDA’s website: https://agriculture.delaware.gov/plant-industries/spotted-lanternfly-quarantine/.