Older adult weevils may be continuing their egg-laying activities, while at the same time, larvae, cocoons, and newly emerged adults may be observed. Upon the arrival of colder weather, adult weevils seek out the crowns of alfalfa plants, or the protections of wooded areas or vegetation provided in ditch banks or fence rows to overwinter. Larvae feed initially on the inside of terminal leaves and then later more to foliage on the lower portion of the plant. Early season larval damage shows up as pinholes in leaf terminals. Damaged leaves dry very quickly giving the field a grayish to whitish cast.
Alfalfa weevils have the ability to severely damage the first cutting of hay in much of Illinois.
In southern areas, significant egg laying may take place during the fall, predisposing some alfalfa fields to early larval damage the following spring. In contrast, alfalfa weevil damage to hay in northern Illinois is likely only if the harvest has been delayed. Injury to alfalfa in the northern portion of the state will most probably occur on the stubble and tender growth of the second crop. Back to Top Scouting Procedures Alfalfa producers in southern and central Illinois should monitor stands very carefully in March, April, May, and June. Alfalfa stands in northern Illinois should be scouted for larval damage in May and June.