Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Alfalfa
Continue to sample for potato leafhoppers on a weekly basis. As temperatures increase you will see an increase in populations. Once plants are yellow, yield loss has already occurred. The treatment thresholds are 20 per 100 sweeps on alfalfa 3 inches or less in height, 50 per 100 sweeps in 4-6 inch tall alfalfa and 100 per 100 sweeps in 7-11 inch tall alfalfa.
Field Corn
As stink bugs move from weeds and wheat into corn, be sure to start sampling corn for this insect pest. Please see the most recent report on stink bug sampling and treatment timing in field corn from North Carolina
https://entomology.ces.ncsu.edu/2016/06/stink-bugs-moving-into-corn/
Soybeans
Be sure to sample the earliest planted fields for bean leaf beetles, potato leafhoppers, thrips, grasshoppers, green cloverworm, silver spotted skippers and spider mites. Grasshopper populations have increased significantly in some double crop fields and in fields with small grain cover crops. If stand reductions are occurring from plant emergence to the second trifoliate, a treatment should be applied. Although no precise thresholds are available, a treatment may be needed if you find one grasshopper per sweep and 30% defoliation from plant emergence through the pre-bloom stage. Numerous products are labeled for grasshopper control in soybeans. Be sure to check all labels carefully before combining insecticides and herbicides since there are a number of restrictions, including cautions on phytotoxicity.