The moths appear all summer long because generations overlap. Moths feed on flower nectar at dusk and fly during daylight hours. There are two or three generations per year. Damage Assessment Damage description Alfalfa loopers are an occasional pest in Alberta. Larvae are present from mid June through September.
Small larvae feed on leaf surfaces and medium-sized larvae eat ragged holes through leaves.
Older larvae feed along leaf margins and may defoliate a large portion of the plant as well as clip flowers and seed pods. The actual decrease in yield that results from this feeding damage is not known. Compensation by plants for such injuries may include continued or additional stooling. The plants may also have more flowers and set more and larger seed. Flower clipping is the most significant problem in canola, but the plant can normally compensate unless severe damage occurs.