Diseases and insect pests of Euonymus tomentosa and its control

As an evergreen shrub, Euonymus tomentosa is one of the most commonly used greening plants in urban streets, squares, parks, unit courtyards and residential green spaces. Because of its different growth environment and extensive management measures, the occurrence of diseases and insect pests is also serious, which seriously affects the urban greening landscape. To investigate and study the occurrence characteristics of main diseases and insect pests of Euonymus tomentosa, the prevention and control measures can be formulated and implemented according to local conditions, so as to control the harm and beautify the environment.

1. Occurrence characteristics of main diseases and insect pests

(1) powdery mildew of Euonymus tomentosa. Powdery mildew is a common disease in seedling cultivation and green belt of Euonymus tomentosa, which mainly occurs on the front and back of leaves. The disease spot is round and white, and the periphery is radial. In severe cases, the small disease spot synthesizes large white powder spots with unclear edges. If the white powder layer is erased, yellow spots can be seen. It causes the leaves to shrink, the disease is slightly twisted, and the leaves fall early.

The pathogen of powdery mildew is fungus, which can also harm other boxwood plants. The pathogen overwintered with hyphae and fruiting bodies on diseased plants or remnants, and conidia could be produced in May of the following year, which could be transmitted by wind and rain. The pathogen of Populus tomentosa can be infected many times during the growing period. High temperature, high humidity and over-dense planting in June and July are beneficial to the development of the disease. The disease decreased in the case of high temperature above 30 degrees Celsius in August, and there was a small peak in autumn.

(2) anthracnose of Populus tomentosa. At the initial stage of the disease, the leaves appeared water-stained yellowish brown dots, the disease key boundary was not obvious, and then the disease spot expanded, the disease site yellowed in the later stage, and small black spots appeared on the disease spot (that is, conidium disc), which were arranged into obvious or inobvious wheel-like patterns, which often caused leaf withering and early defoliation. The pathogen of anthracnose is a fungus, which overwinters with conidia disk in diseased body and soil, and can also overwinter with conidia and mycelium on diseased plant tissue. At the end of the following spring, the conidia were transmitted by insects and wind and rain, and the conidia invaded from stomata or wounds. Populus tomentosa could be repeatedly infected during the growing period, and the disease was the most serious in summer and autumn every year. Generally, the disease is aggravated under the condition of more plant wounds, too dense plants, poor ventilation, excessive application of nitrogen fertilizer and weak plant growth.

(3) Japanese tortoise wax scale. It belongs to the family Homoptera Coccidae. In addition to harming Euonymus tomentosa, it can also harm more than 150 kinds of woody flowers and fruit trees, with miscellaneous feeding habits and strong fecundity. When the damage is serious, the host and the back of the leaves are covered with worms, which often cause mildew and fouling, resulting in plant weakness and even death.

The insect produces one generation a year, overwinters as fertilized female adults on the branches, and begins to lay eggs in May the following year. The eggs are laid in the scale shell in the first and middle of June, and each female adult can lay about 1000 eggs on average. The egg period is about 20 days. The nymph hatching peak period is from late June to mid-July. The newly hatched nymphs climb to the leaves, fixed to suck the juice, and then secrete wax, and then gradually form a star-shaped scale shell. After more than one month of damage, the waxy scale shells of female and male nymphs changed obviously. The 2-year-old male nymph emerged into a male adult in early September and died after mating, while the female nymph 3-year-old gradually migrated from leaves to branches with molting, and overwintered in late October after fertilization.

(4) Tetranychus urticae. It belongs to the family Tetranychidae. It can harm more than 100 kinds of flowers, trees, fruit trees and crops. Piercing harm to the leaves, the leaves appear green and yellow spots, resulting in the leaves without luster, early shedding.

About 10 generations occur every year in the northern region. Fertilized female adult mites overwintered in soil cracks and bark cracks, and began to breed in the following spring. Mainly for bisexual reproduction, such as the lack of male adult mites can also be parthenogenetic, its offspring are male. Each female mite can lay more than 100 eggs on average. In July and August, it propagates rapidly in high temperature, drought and little rain, the harm is rampant, and it is easy to cause disasters. The mite has the habit of spinning and drawing the net and often lives under the silk net near the main vein of the back of the leaf. Overwintering in October.

two。 Comprehensive prevention and control methods. As long as the above diseases and insect pests are prevented in time according to the occurrence law of the above diseases and insect pests, the harm can be significantly reduced and even effectively avoided.

(1) eliminate the source of insect bacteria. Combined with shaping and pruning, withered branches, diseased branches, insect-bearing branches were removed and burned centrally, so as to reduce the source of bacteria and insects.

(2) strengthen management. Seedlings and greening planting should not be too dense, improve ventilation and light transmission conditions; avoid plant wounds as far as possible in management and operation; do not apply too much nitrogen fertilizer, increase phosphorus and potassium fertilizer. Create unfavorable conditions for disease infection and improve the ability of plant disease resistance and insect resistance.

(3) Chemical control. It was carried out in the early stage of disease onset and the early onset period of young pests. Powdery mildew can be sprayed with 2000 times of 20% triadimefon EC, anthracnose with 500800 times of anthrax Fumei wettable powder, tortoise wax scale with 1000 times of 40% omethoate EC or 50% malathion EC of 600800 times. Two-spot leaf mites can be sprayed with 1.8% avermectin or 3000 times. If a variety of diseases and pests occur, you can use the above agents mixed spray, both for treatment.