If you get some lodged grain, that's where you're more likely to find them in the highest numbers. Patch spraying is an option when armyworms are concentrated in areas of dense or lodged grain. Gavloski said the technique seemed to be successful in Manitoba last year. As far as I know, they didn't have to go back and spray those fields a second time. However, he said patch spraying works only if armyworms are highly concentrated in specific areas of the field, which is not always the case.
Sufficient field scouting is needed to decide on the most economical control.
Patch spraying can also be used in fields where cutworms become a concern. An area around the infected patch should also be sprayed to help prevent the cutworms from spreading. Insecticide resistance Gavloski emphasized the need to rotate families of chemicals, which reduces the risk of pest insects developing resistance to chemicals registered to control them. Insecticide resistance is of greatest concern in crops where spraying is done year after year for the same nuisance insect, such as in potato crops affected by Colorado potato beetles. Rotating between insecticides in the same chemical family is not considered resistance management, since the method of killing insects is often the same.