They overwinter as adults in field trash or other secluded hiding places and emerge in late winter or early spring. They are pale green with a thin white line down the center of the back and have a brown head. Larvae complete their growth in about 3 to 4 weeks. In most years, there is only one generation. They may cause extensive damage in certain situations such as in fields where the larval population was not treated and in other situations where the reason is not always clear.
Damage is characterized as extensive skeletonization of the leaves in spring and early summer.
The alfalfa weevil causes damage to first and occasionally to second or third cuttings. Before the Egyptian alfalfa weevil invaded California and spread into most of the areas occupied by the alfalfa weevil, B. curculionis effectively suppressed alfalfa weevil populations in the mid-coastal area. Serious damage can sometimes be prevented by cutting the crop as soon as most of the plants are in the bud stage. On short alfalfa early in the season, or on stubble following cutting that cannot be checked with a sweep net, treatment is indicated when growth is retarded because of weevil feeding. The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies.