The species Heliothis virescens is commonly known as the tobacco budworm and is found in Southern Canada during the summer months. The tobacco budworm is a pest of field crops, such as alfalfa, flax, soybean and tobacco; however it has been known to attack vegetable crops as well. This species feeds on the leaves, buds and flowers of these crops.
The eggs of the tobacco budworm, which are spherical with a flat base, are deposited on blossoms, fruit and terminal growth. The eggs are initially white, but will turn grey and darken as they mature. The larvae range from 1-35 mm in length depending on its developmental stage from 1st to 6th instar. The young larvae are yellow in colour and with maturity, turn greenish with a brown head. The mature adult moth is brownish in colour and has a light tint of green. At this stage, it can range from 25-35 mm in length.
To monitor for budworm and detect early stages of an infestation, check buds and flowers for small holes. Tobacco budworm larvae are most active during dusk and best discovered at this time. During daylight hours, they often hide around the base of the plant. An application should be performed when an infestation ranging from 10-15% of very small larvae is found in the leaves or the buds of the crop to prevent the presence of bigger larvae that can produce a significant damage to the crop plant.