Adult body length 10 ~ 18 mm, wing spread 15 ~ 26 mm, grayish black. The antenna is filiform, the compound eye is black, the scales on the back and side of the chest are raised, the outer edge line of the front wing is grayish white, there are nearly triangular black spots on the front edge, there are black eye spots in the middle of the rear edge, and the spots are short eyebrows, the inner horizontal lines are parallel black double lines, and the rear wing is light grayish brown and shiny. The egg is 0.6 ~ 0.8 mm in diameter, steamed bread-shaped, with a big round cake-like protrusion at the top. The first egg is white, and it was gray before hatching. The last instar larvae are 12 ~ 16 mm in length, brown or brownish green, and the back plate of the forechest is dark brown. There are 6 hairs on the back of the 2nd ~ 3rd section of the trunk, which are arranged horizontally in a straight line, with 3 hairs on each side; There are four trapezoidal hairs on the back of the 4th ~10 section of the trunk. From 1 1 to 12, the back hair is large, slender and soft, and the base is brown and nodular. The ossification area of gluteal plate is inverted trapezoid and dark brown. The pupa is 8 ~ 10 mm long, oval, yellow-brown, with dark brown back, and coated with white powder in vitro. Cocoon spindle-shaped, about 1 1 mm long, white, with tawny fluff.
Three generations a year. Mature larvae cocoon and pupate in the cracks of bark, and some pupate in the shed shell of chestnut. 1 generation lays eggs on new shoots, tender leaves and female flowers (young buds) from late May to early June, and the egg period is mostly 4 days. Larvae harm buds and flowers, eat buds and make them dry and fall off. Larvae first harms the tender leaves, and then harms the tender branches. Mature larvae cocoon and pupate damaged new buds, male flowers and leaves with silk. In late June, the adults emerged and laid the second generation eggs. The peak of spawning is in early and middle July, and the peak of damage is in middle and late July. The third generation eggs lay eggs in chestnut shed in the middle and late August. The egg period is usually 3 days. Hatched larvae generally do not eat directly in chestnut shed, but often eat under the thorns of bracts, and the injured bracts dry up and fall off, which is obviously harmful, but the total bracts generally do not fall off. It is harmful for larvae to eat bracts after 2 ~ 3 years old. The damage peak of the second generation larvae is in the middle and late July, when the young fruits in the bracts begin to grow and are almost eaten up. After 23 ~ 27 days, the larvae mature into pupae. The adults of Spodoptera exigua emerged at 7 ~ 8 pm, moved at night, stood still during the day, and had no preference for sugar, vinegar and ordinary light. The average life span is 3.5 days, and the sex ratio is 1: 1. In the first half of September, the mature larvae pupate and overwinter.
Prevention and control methods: ① Scrape bark in autumn and winter, remove fallen leaves from chestnut orchard, eliminate overwintering pupae, and manually cut damaged chestnut bracts in the early stage to reduce insect sources; ② In the first half of June, 1 generation eggs hatch about 60%, and in the second half of July, when 70% ~ 80% eggs hatch, spray 90% trichlorfon or 50% dichlorvos 1000 times solution twice, or spray 3,000 ~ 4,000 times solution of pyrethroid pesticides to kill 50%.