Beet webworm moth

Beet webworm moth is a common, medium sized, roughly triangular (deltoid) moth. It occurs throughout the United States and southern Canada, but it is mostly absent from the southeast.

Adults are active from May to September. They are found in fields, gardens, and waste places. The larvae feed on the leaves and tender stems of many species of broad-leaved herbaceous plants, including wormwood, lambsquarters, and clover. They are a pest of many agricultural crops, attacking the leaves of soybeans, sunflowers, tobacco, flax, and oats, and damaging the roots of sugar beets and carrots. They also attack many garden plants, including lettuce, spinach, onion, and bell pepper.

Adults are ½″ (13 mm) in length and have a 15⁄16″ to 1⅛″ (24 to 29 mm) wingspan. The body is slender.

The sensory mouthparts (labial palps) are moderately long and are projected forward. The compound eyes are large. The simple eyes (ocelli) are small but well developed.

The forewing is broadly triangular. The ground color is variable, light brown, grayish brown, yellowish brown, reddish brown, or dark brown. The markings consist of pale gray spots and lines and dark blotches. They are variable in number and intensity, and they are sometimes almost completely absent. The discal spot is whitish. The round spot in the upper median area (orbicular spot) and the kidney-shaped spot (reniform spot) in the lower median area have broad dark borders, and they are separated by a pale, rectangular patch. The postmedial (PM) line is yellowish and very wavy. The subterminal (ST) band is yellowish and it is abruptly expanded near the middle. The fringe is also variable. It may be gray, brown, or black. It can be pale at the base, dark in the middle, and pale at the tip, to almost entirely dark.

Total length: ½″ (13 mm)

Wingspan: 15⁄16″ to 1⅛″ (24 to 29 mm)

Alfalfa webworm moth (Loxostege cereralis) forewing has black wedges, lines, and streaks. The
ST band is evenly curved to an expanded middle.

Fields, gardens, and waste places

May to September

Many species of herbaceous plants