The presence of behavioral and ecological plasticity, high tolerance to pesticides and voracious feeding habits by larvae and adults has made the alfalfa weevil a formidable pest of alfalfa for many years. Biology of the Pest Adults are 5-6 mm long and have a snout. A female may lay 500-2000 eggs in her lifetime. Clutches of 1-40 eggs are laid inside the stem of dead host plants. Eggs range from white to yellow.
Young larvae are legless and light yellow-green.
Although young adults have a distinctive black line running down the back, they darken as they age and may be quite variable in coloration. The head darkens to black as the larvae age and a white stripe becomes evident down the back. There are also white lateral stripes on the older larvae. Alfalfa weevil feeds on several varieties of clover in addition to alfalfa. Populations of this pest are highest in the alfalfa-growing regions of the country, though the distribution includes all 48 contiguous states.