Laphygma exigna Hübner, also known as beet armyworm, belongs to the family Lepidoptera and the family Spodoptera exigua. Distributed in Liaoning, Hebei, Inner Mongolia, Qingdao, Taiyuan, Xi'an, Ningxia, Jiangsu and Zhejiang. Damage to chrysanthemums, marigolds, carnations, carnations, camellias, gerbera, paulownia and arborvitae, etc.

Damage

The larvae feed on leaves and eat flower buds and corollas, causing leaf nicks and bud drop.

Morphological characteristics

The adult body is about 13 mm long, grayish brown, with rusty brown forewings and black wavy lines. The outer line is a zigzag black double line, and the ring pattern is yellow with black edges. The kidney stripes are yellow in the middle and brown with black edges. Hind wings white with grayish brown edges. Oval steamed bun shape, white. Mature larvae are about 22 mm in length, and their body color varies depending on the region or host. Generally dark brown, yellowish brown, green, etc. The topline of the body is obvious. The lower line of the valve is light yellow, and there are obvious white spots behind and above the valve. The pupa is yellowish brown and has two curved anal spines.

Occurrence characteristics

Five generations occur in one year. Overwinter as pupae in the soil. The adults lie dormant during the day and emerge at night, and have phototaxis. Eggs are laid on leaves or weeds. There are dozens to hundreds of eggs in overlapping blocks. Newly hatched larvae swarm near egg masses, spin silk and pull nets to feed on leaf mesophyses. After 3 years of age, the damage spreads, and some of them penetrate into flower buds and corollas. The larvae lie dormant during the day and emerge at night, with the ability to appear dead. High temperature resistance and poor cold resistance. Therefore, the damage is serious from July to August. In September, mature larvae enter the soil, spin silk, build chambers, pupate and overwinter. This insect occurs intermittently in the north, but can occur throughout the year in Guangzhou and Hainan.

Control methods

See Spodoptera exigua control.