As the first harvest approaches, most weevil larvae spin cocoons in debris on the soil surface and enter the pupal stage. Adult weevils emerge approximately 10 days after the onset of pupation. These adults may feed on foliage for short periods of time, usually on regrowth after first harvest. Occasionally, damage by adults requires spraying of the second crop. Normally, high temperatures and limited cover after first harvest cause weevils to leave fields and begin summer aestivation.
Adults move into vegetation along field margins where they remain inactive until fall.
Relationship Between Alfalfa Weevils and Yield on First and Second Cuttings. In recent studies on alfalfa yields under separate and combined effects of weevils and weed encroachment, researchers have shown that controlling alfalfa weevils allows plants to more effectively compete with weed species. When current economic thresholds are used, the combined benefits of alfalfa weevil and weed control have shown the greater savings in forage yields and stand retention than either type of pest control conducted alone. This sampling procedure takes into consideration prevailing temperatures, alfalfa growth stage, and weevil development and populations. Measure the height of 10 stems from each 30 stem sample.