Larvae are pale green with a white stripe on the back and a shiny black head. Young larvae feed in the tightly folded leaves of stem buds. Larger larvae move onto open leaves near the terminals. Peak damaging larval populations often coincide with the first cutting of the crop. Pupation occurs in plant crowns and soil debris.
New adults feed for a short time, then become inactive.
A second generation of larvae has been observed but is not considered to be important. Heavily infested stands have a grayish or frostlike appearance due to the dried, defoliated leaves. At high weevil densities, foliage can be stripped, leaving only skeletonized and ragged leaf fragments and stems. Yield losses of 30 to 40 percent are possible. Hay quality is lowered due to loss of leaf tissue, leaving only stems.