Managing insect pests in cole crops presents unique challenges because of the variety of pests involved and the diversity of the crops themselves. Complicating things further, various pests show their presence at different times during the growing season (see “Insect Pests Of Cole Crops” chart). Overall, a key to effective pest management is regular scouting of the crop to determine pest presence and abundance.
At least five different areas of the field should be chosen, and 10 to 20 plants inspected for pests and/or damage. In addition, yellow sticky traps placed in and around cole crop fields early in the growing season can alert growers to the presence of cabbage maggot flies and flea beetles.
Traps should be changed at least weekly. Another valuable scouting tool is pheromone trapping. Pheromones are scents produced by female moths that attract males for mating. Synthetically produced pheromones can be purchased and used in traps to assess the presence and abundance of diamondback moths and cabbage looper. Yellow sticky traps and pheromone traps and lures may be purchased through several sources, including Great Lakes IPM, Gemplers, and others.
Stay On A Schedule
Regular scouting helps growers determine when pests are at threshold. The treatment threshold is the pest population level at which control measures must be initiated to prevent economic damage. Treatment threshold usually varies with crop type and growth stage. Thresholds have not been determined for every pest. For example, there are no treatment thresholds for flea beetles or onion thrips. In these cases growers can use their judgment when evaluating crops.
An integrated approach to insect pest control makes use of all effective control strategies in a complementary way (see “Take Control Of The Pests In Your Cole Crops” chart). Cultural control methods (crop rotation, resistant varieties, trap cropping, etc.) can reduce pest numbers and reduce or eliminate the need for insecticide application. When necessary, insecticides should be chosen carefully, so as not to impact biological control agents.