The forewings of adult tomato moths (Lacanobia oleracea) are a reddish-brown with a feint light brown, kidney-shaped marking, and a thin, toothed white line along the posterior edge of the forewing. As in most noctuid moths, the hindwing is greyish and lighter than the forewing, with a darker shadow at the margin. The antennae are long and thin. Head and thorax are reddish-brown while the abdomen is a lighter grey-brown.
The females of the tomato moth (Lacanobia oleracea) deposit their spherical eggs on the underside of leaves in groups of 50 to 300, often arranged in layers. The eggs are greenish at first, but gradually change to a light yellow or almost white. There are six larval stages. The head is a pale green in the first two larval instars, later becoming white to grey-brown with mottled markings. The pattern of markings on the larvae varies according to the host plant and developmental stage. At first, the body is a glossy green. Later, a conspicuous yellow longitudinal stripe with black dots above is visible on either side. The yellow stripe is bordered at the top by a narrow gray stripe. Older larvae may vary from light green to light brown, or even a reddish colour with three dark grey dorsal stripes, partly overshadowed by the underlying grey-black stripes. Each segment has several darker stripes both laterally and dorsally.
When about to pupate, the caterpillars seek a protected place just below the ground surface or under rockwool matting. A light, loose silk cocoon is spun and two or three days later a red-brown pupa is formed, which gradually turns a glossy black. The moths are nocturnal, hiding during the day in fissures in the ground, and are often only seen when they are startled, such as during crop watering. The larva also feeds almost exclusively at night.