The most common diseases and insect pests of Populus tomentosa

1. Yellow poplar silk leaf borer

The larvae spin silk to connect the surrounding leaves and twigs as temporary nests, and then feed on them. In serious cases, the leaves are eaten up, resulting in the death of seedlings.

Morphological features: adult body wings are gray-white, the front, outer and trailing edges of the wings are purple-brown wide band, there are two white spots on the leading edge of the purplish brown belt, the scales are shiny, and the purplish red shines. The head of the larva is black, the carcass is yellowish green, the topline, subtopline and valve line are dark green to dark green, and the valve line is orange.

Occurrence regularity: 2 to 3 generations a year in the northern region, overwintering with larvae forming thin cocoons in the bud, adults dormant during the day and out at night, with phototaxis.

Prevention and control methods: (1) artificial killing: in the adult oviposition period, combined with seedling pruning, removal of egg blocks, buds, concentrated burning. (2) using black light to trap and kill in the adult stage. (3) when the larva damage is serious, spray 50% fenitrothion emulsion 1000 times, or 4.5% cypermethrin 2000 times; Bt emulsion 500x spray (note: Bt emulsion is strictly forbidden to be used at the same time with fungicides, the effect is better after 4: 00 p.m. on a cloudy day).

2. Big leaf yellow poplar inchworm

The larvae gather the leaves to feed, and after eating all the leaves, they eat the skin of the twigs, resulting in the death of the whole plant. Overwintering with pupa, the flying ability of adults is not strong, and has strong phototaxis.

Morphological features: adult, female adult wing bottom silver-white, with light gray lines, different sizes, irregular arrangement. The outer edge of the forewing has a continuous light gray pattern, the middle line is not in line, there is a large spot at the end of the middle chamber, the wing base has a deep yellow, brown and gray spot, the abdomen is golden yellow, and nine lines of stripes are composed of black spots. The male moth has 7 lines of stripes on its abdomen. All the larvae are black, the forechest dorsal plate is yellow, there are 5 square black spots, and the valve line and ventral line are wide, which are yellow.

Control methods: (1) making use of the phototaxis of adults, light trapping was carried out in the adult stage. (2) spraying 50% fenitrothion EC or 4.5% cypermethrin 2000 times during the larval damage period. (3) to eradicate the egg mass during the spawning period. Turn the root soil in winter and kill the overwintering pupae.

3. Japanese tortoise waxsuke

It occurs one generation a year, overwintering with fertilized female adults on shoots.

Morphological features: female adult, wax shell gray or slightly fleshy red, oval. Male adult with a dark brown or brown body and a deep dorsal plate of the head and chest. Nymph, wax shell oval to oval, back slightly raised.

Prevention and control methods: (1) Quarantine measures: when purchasing seedlings in different places, plant quarantine procedures must be strictly carried out to prevent the artificial spread of pests. (2) strengthening garden maintenance and management: through maintenance and management, to create environmental conditions that are not suitable for the survival of shell insects. Implement rotation planting, clear the garden in time, burn deciduous leaves, weeds, disease and insect branches, reduce the population number of overwintering pests, apply fertilizer reasonably, and enhance plant resistance. Reasonable pruning, make it ventilated and transparent, change the living environment, weaken its fecundity and reduce the harm. (3) Chemical control: when the insect population density is not high, you can use a soft brush dipped in a small amount of dichlorvos plus water (1:50 to 100x liquid) to kill. During the nymph outbreak, spray detergent diesel emulsion; 150 to 200x neem oil emulsion; 1000 to 2000 times oxymatrine; 2000 to 2500 times vigorously, spraying once every 10 days or so, three times in a row. (4) protect parasitoids and other natural enemies.

4. Peach powder aphid

Wingless female aphids and nymph aphids are harmful to sucking juice on the back of branches and young leaves, and there are often white waxy secretions on the affected leaves, which are easy to cause coal fouling disease, and when serious, the branches and leaves turn black, affecting plant growth and ornamental value. About 10 generations occur in Tangshan area every year.

Prevention and control methods: (1) protect ladybugs, lacewings and other natural enemies. (2) Chemical control: 2000 times of 20% chrysanthemum EC or 2000 to 3000 times of imidacloprid powder can be sprayed.

5. Powdery mildew

Damage to the leaves of Euonymus tomentosa, the leaves of the damaged plants showed wrinkling deformities, affecting the growth. Powdery mildew is mostly distributed on the front of the leaves of Euonymus tomentosa, rarely growing on the back of the leaves, the single spot is round, and the white spot is irregular after expanding and healing each other.

Prevention and treatment methods: (1) proper pruning to enhance permeability. (2) in the early stage of the disease, 25% trimethoprim 1300-fold solution, 70% methyl topiramate 700-fold solution and 50% acetaminophen wettable powder were sprayed alternately. If the disease is serious, it must be pruned, cut off the diseased leaves and burn them centrally, and then spray chemicals to prevent and cure them.

6. Leaf spot of Euonymus tomentosa

When the harm is serious, it will cause the leaves of boxwood to fall ahead of time, form bald branches, affect ornamental, and even cause death.

The disease occurs on the new leaves, and after producing small yellow spots, it expands into irregular large spots, the edge of the spot is raised, and the brown edge is wide. There is an extended yellow halo outside the edge of the bulge, with taupe or taupe in the center, covered with black dots.