Control of diseases and pests of diamondback moth in walnut tree

   1. Distribution and damage symptoms are omnivorous pests. The common pests are Spodoptera litura, Plutella xylostella, Spodoptera litura and Spodoptera litura, which are distributed all over the country. Feeding on leaves by larvae affects tree potential and yield, and is an important pest of walnut leaves. The lower instar larvae feed on the lower epidermis and mesophyll, leaving only reticular transparent spots on the epidermis and reticulate leaves. When the larvae grow up, they disperse the damage, and eat the leaves into niches, leaving only the main vein and petiole, or even all of them.

   2, morphological characteristics and living habits

   (1), also known as spicy seeds, caterpillars, star anise, adults 13-17 mm long, wingspan 29-36 mm, yellow, antennae filiform, brown, mature larvae yellowish green, 18-25 mm long, about 8 mm wide, with two dumbbell-shaped purple-brown markings on the back, branches on the body, poisonous hairs on the thorns. The egg is oblate, yellowish, 1.4 mm long, pupa oval, about 12 mm long, hard, grayish white, with dark brown longitudinal stripes.

   mostly occurs one generation a year in Northeast and North China, and two generations a year in Henan, Shaanxi and Sichuan. Overwintering with mature larvae in hard cocoons on branches and branches. The adults have phototaxis, fall in the daytime and come out at night, mate immediately after Eclosion, lay eggs soon, and often lay in the proximal end of the back of the leaves.

   (2) the adult of Plutella xylostella is about 18 mm long and grayish brown. The front wings are brown, with two dark brown arcs, and the two lines are light. There is a copper triangular spot between the outer horizontal line and the hip angle. The egg is flat, oval, yellow. The larva is 35 mm long and green. Cocoons broadly ovoid, grayish brown. The insect produces 1 or 2 generations a year and overwinters as mature larvae in the soil.

   (3) the adult is 16 mm long and the wingspan is about 36 mm. Most of the adults are green, the compound eyes are dark brown, the antennae of the female moth are filamentous, the antennae of the male moth are short-feathered, and there is a light brown longitudinal pattern in the center of the back. Eggs are flat oval, about 2 mm long, milky white at birth, gradually yellowish green, mostly 10 pieces, fish scales arranged. The mature larvae are 24 ~ 27 mm long and grow slightly in a tube. The pupa is about 13 mm long, oval, yellowish brown.

One generation of    occurs every year in Northeast and North China, and two or three generations occur in the south of the Yangtze River. The old larvae overwinter with cocoons in the root neck of the stem. After maturing, the larvae overwintered with cocoons on the trunk or in the shallow loose soil layer under the tree and in the grass. The adults had phototaxis, and the eggs were mostly laid on both sides of the main vein on the back of the leaves. The newly hatched larvae ate the eggs first and then the mesophyll.

   (4) is also known as Spodoptera litura. The adult body is 16 mm long, the wingspan is 28-39 mm, the antennae are filamentous and the body is grayish brown. Ovate oblate-elliptic, ca. 1.5 mm, yellowish white. The mature larvae are 2528 mm long, oval in shape and yellowish green. There is a red dot on each side of the fourth segment of the body, and there are bristles on it. Pupa flat-elliptic, ca. 13 mm, yellowish brown.

One generation of    occurs every year in the northeast, two generations in the middle and lower reaches of the Yangtze River, and three generations in the south. All the larvae survive the winter with the cocoon under the tree, and the adults lay eggs on the leaf surface after Eclosion. After hatching, the larvae eat eggs, then eat mesophyll, and the larvae feed day and night. After maturing, they enter the soil to make cocoon pupation.

   3. Prevention and control methods

  ① eliminates overwintering cocoons. Can be combined with autumn tree plate fertilization and winter pruning and other management to eliminate overwintering cocoons.

  ② black light trap. During the occurrence period of overwintering adults from the middle of June to the middle of July, black light was set up to trap and kill adults in the field.

Artificial prevention and treatment of   ③. When the small larvae gather on the back of the leaves in the first ten days of July, the leaves can be cut off in time to kill the young larvae; in the middle and late August, the mature larvae look for a suitable place for cocooning on the bark of the branches, and concentrate on capturing the mature larvae and killing them.

  ④ biological control. Shanghai green wasp is the dominant natural enemy of Spodoptera litura, which can be protected and used to eliminate the mature larvae in the overwintering cocoon.

Chemical control of   ⑤. When the damage to the larvae is serious, spray 25% imidophos EC 600 times or 2.5% deltamethrin emulsion 5000 times during the larval occurrence period.