We have quite a bit of conventional field corn in Arkansas this year and have been getting questions on when to spray for fall armyworm, corn earworm, and southwestern corn borer. First, I will address corn earworm and fall armyworm.
Treatment is warranted for these two pests when we find 3 to 6 larvae per plant during the whorl stage. Let me repeat that. We only treat for corn earworm and/or fall armyworm during in whorl stage in corn. Currently, most, if not all, of our field corn is past this stage.
Treating for corn earworm infestations in the ear on field corn is not economical or necessary. We conducted research several years ago looking at potential yield loss from corn earworm in field corn and could not measure any significant loss in yield from corn earworm infestations in the ear. Therefore, it is not necessary to treat for corn earworm infestations in the ear, no matter how effective the insecticide may be.