Detailed Guide to the Main Pest and Disease Control Methods for Euonymus japonicus

Euonymus japonicus, as an evergreen shrub, is one of the most commonly used landscaping plants for urban streets, plazas, parks, institutional courtyards, and residential green spaces. Because its growing environment conditions vary greatly and management measures tend to be extensive, its pests and diseases also occur and cause damage rather severely, seriously affecting the urban landscaping landscape. Investigating and studying the occurrence characteristics of the main pests and diseases of Euonymus japonicus allows for the formulation and implementation of control measures suited to local conditions, achieving the goal of controlling damage and beautifying the environment.

1. Occurrence characteristics of the main pests and diseases

(1) Euonymus japonicus powdery mildew. Powdery mildew is a common disease in Euonymus japonicus seedling beds and green belts, mainly occurring on the upper surface of leaves, and occasionally on the underside as well. The diseased spots are round and white, with a radial margin; in severe cases, small spots merge into large white powdery patches with indistinct edges, and after wiping off the white powdery layer, yellow spots can be seen. This causes leaf shrinkage, slight distortion of diseased shoots, and premature leaf fall.

The pathogen of powdery mildew is a fungus, which can also harm other Euonymus species. The pathogen overwinters as mycelium and fruiting bodies on diseased plants or diseased remains, and in May of the following year can produce conidia, which spread by wind and rain. During the growing period of Euonymus, the fungus can infect multiple times; high temperature and high humidity in June-July and overly dense planting favor disease development. When temperatures exceed 30 degrees Celsius in August, the disease declines, and in autumn a small peak of incidence appears again.

(2) Euonymus japonicus anthracnose. In the early stage of the disease, water-soaked yellowish-brown small spots appear on the leaves, with an indistinct boundary between diseased and healthy tissue; afterward the spots expand, and in the later stage the affected area turns yellow, with small black dots (acervuli) appearing on the spots, arranged in obvious or indistinct concentric rings, often causing leaf blight and premature leaf fall. The pathogen of anthracnose is a fungus, which overwinters as acervuli in diseased remains and soil, and can also overwinter as conidia and mycelium on diseased plant tissues. In late spring of the following year, conidia spread by insects and wind and rain, and the conidia invade through stomata or wounds; during the growing period of Euonymus, repeated infection can occur multiple times, with the most severe incidence each year in summer and autumn. Generally, the disease worsens when there are many wounds on the plants, the plants are too dense, ventilation is poor, nitrogen fertilizer is applied excessively, and the plants grow weak and spindly.

(3) Ceroplastes japonicus. It belongs to the order Homoptera, family Coccidae. In addition to harming Euonymus japonicus, it can also harm more than 150 other woody ornamental flowers and fruit trees; it is highly polyphagous and has strong reproductive capacity. When damage is severe, the host's new shoots and leaf undersides are covered with the insects, often triggering sooty mold, causing the plants to weaken or even die.

This insect has 1 generation per year, overwintering as fertilized adult females on branches. In May of the following year, they begin laying eggs, with mid-to-late June being the peak egg-laying period. Eggs are laid inside the scale cover, and each female adult can lay about 1000 eggs on average, with an egg period of about 20 days. Late June to mid-July is the peak hatching period for nymphs. Newly hatched nymphs crawl onto leaves to cause damage, settle to pierce and suck sap, and afterward secrete wax, gradually forming star-shaped scale covers. After more than 1 month of damage, the waxy scale covers of male and female nymphs change noticeably. Male nymphs reach the 2nd instar and emerge as adult males in early September, dying after mating; female nymphs reach the 3rd instar, and with each molt gradually migrate from the leaves to the branches to cause damage, and after fertilization begin overwintering in late October.

(4) Two-spotted spider mite. It belongs to the order Trombidiformes, family Tetranychidae. It can harm more than 100 species of ornamental flowers, trees, fruit trees, and crops. It pierces and sucks sap to cause damage, causing chlorotic yellow spots on leaves, making the leaves lusterless and causing early shedding.

In northern regions, about 10 generations occur each year, overwintering as fertilized adult females in soil crevices, bark crevices, and similar places, and beginning reproduction in spring of the following year. It mainly reproduces sexually, but when male adults are lacking it can also reproduce by parthenogenesis, and all offspring are male. Each female mite can lay more than 100 eggs on average. In July-August, when temperatures are high and drought with little rain occurs, it reproduces rapidly and causes rampant damage, readily leading to outbreaks. This mite has the habit of spinning silk webs and often rests under the silk webs near the main veins on the underside of leaves. It enters overwintering in October.

2. Integrated control methods. As long as prevention is carried out in a timely manner according to the occurrence patterns of the above pests and diseases, their damage can be significantly reduced and can even be effectively avoided.

(1) Eliminate insect and pathogen sources. Combined with shaping and pruning, remove dead branches, diseased and deformed branches, and insect-bearing branches, and burn them in a centralized manner to reduce pathogen and insect sources.

(2) Strengthen management. Seedling raising and landscaping planting should not be too dense, and ventilation and light conditions should be improved; during management operations, try to avoid causing wounds on the plants; do not apply excessive nitrogen fertilizer, and increase the application of phosphorus and potassium fertilizers. Create conditions unfavorable to disease infection and improve the plants' disease and pest resistance.

(3) Chemical pesticide control. Carry it out in the early stage of disease onset and the early outbreak stage of young pests. For powdery mildew, 20% triadimefon emulsifiable concentrate at 2000 times dilution can be sprayed; for anthracnose, 80% carbendazim-thiram wettable powder at 500-800 times dilution can be sprayed; for Ceroplastes japonicus, 40% omethoate emulsifiable concentrate at 1000 times dilution or 50% malathion emulsifiable concentrate at 600-800 times dilution can be sprayed; for two-spotted spider mite, 1.8% abamectin or 15% fenbutatin oxide emulsifiable concentrate at 3000 times dilution can be sprayed. If multiple pests and diseases occur together, the above agents can be mixed and sprayed for simultaneous control.