The recent snow and cold should have little effect on developing alfalfa weevil populations. Temperatures must drop below minus 7o to minus 10o F to be lethal to eggs deposited in plant stems. Small larvae are killed by temperatures of around 0o to minus 5o F. Larger larvae are more vulnerable, succumbing at 10o to 15o F.
Alfalfa stems and leaf tips provide some protection, so temperatures in the plant canopy are probably a little warmer than the air temperature. In addition, snow cover provides some insulation.
By Lee Townsend, Extension Entomologist