Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Cabbage
Be sure to watch for imported cabbage worm (ICW) and diamondback moth larvae (DBM) within a week of transplanting. As a general guideline, treatment is recommended if you find 5% of the plants infested with larvae. If DBM is the predominant species, be sure to select an insecticide that is effective for this insect pest since it can be difficult to control. The pyrethroids have not provided effective control of DBM in many cases, especially where resistance has been documented. Please refer to the Commercial Vegetable Recommendations for suggested chemical controls: http://extension.udel.edu/ag/files/2012/03/ColeCrops.pdf.
Peas
Fields should be sampled on a weekly basis for pea aphids. The current cool weather will favor an increase in populations. On small plants, you should sample for aphids by counting the number of aphids on 10 plants in 10 locations throughout a field. On larger plants, take 10 sweeps in 10 locations. As a general guideline, a treatment is recommended if you find 5-10 aphids per plant or 50 or more aphids per sweep.
Potatoes
As soon as plants emerge, be sure to sample fields for Colorado potato beetle adults, especially if an at-planting material was not used. A treatment should not be needed for adults until you find 25 beetles per 50 plants and defoliation has reached the 10% level.