Treatment level curve based on percent aphid infested plants and number of days until harvest Caterpillars Several different spicies of caterpillars can attack sugar beets at various times during the growing season. Some of the more common ones are the variegated cutworm, loopers, zebra caterpillars, western yellow-striped armyworm, beet webworm, and beet armyworm. All of these caterpillars defoliate the plant to some extent. The age and size of the sugar beet plant should be consided when determining if a treatment should be applied to control these caterpillars. Young plants can often recover from caterpillar feeding without much yield loss.
Old plants can lose some leaf tissue without yield loss.
Plant defoliation diring the middle of the season appears to be the most critical period. General guidelines for making control decisions are presented in Table 2. The age and growth potential of the plant and amount of leaf surface consumed by caterpillars were taken into account when developing the table.