Alfalfa weevil is a major alfalfa pest in Ontario. Larvae feeding on alfalfa leaves can reduce both yield and forage quality. The simple answer As alfalfa gets taller it can tolerate more weevils before action is necessary to protect forage yield and quality. Action thresholds for managing alfalfa weevil are as follows: Stem Height Number of larvae per stem Up to 30 cm (12 in.) More than 1 Up to 40 cm (16 in.) 2 or more Any height More than 3 A little more information Alfalfa weevil larvae begin feeding in mid- to late-May, beginning with the leaf buds. The larvae then move to leaves near the stem tips, where damage starts off as pinholes (Figure 1) and progresses…
