Control Methods and Techniques for Leaf Spot Disease in Japanese Euonymus

Japanese euonymus (Euonymus japonicus) is a commonly used evergreen ornamental small shrub in landscaping, with many advantages, but the occurrence of leaf spot disease causes premature leaf drop, resulting in bare branches and even death, seriously affecting the normal growth and ornamental effect of Japanese euonymus.

1. Symptoms: In the early stage of the disease, small yellow spots appear on the leaves, gradually turning yellow-brown, expanding into circular or irregular spots, with a lesion diameter of 2 mm to 10 mm. In the later stage, the lesions become gray-brown or gray-white with darker edges, and many small black dots form on the lesions. In severe cases, the lesions merge into one piece, and the leaves turn yellow and fall off.

2. Disease occurrence pattern: The pathogen overwinters as mycelium and other forms on diseased leaves or fallen leaves, serving as the primary infection source. Spores are spread by wind and rain. In the following spring, as temperatures rise, conidia are produced and invade through stomata, pruning cuts, or wounds. In the Hebei region, infection generally begins in June, with the peak infection period in July and August. Symptoms appear in mid-August, and the disease is severe from mid-to-late August to September, with lesions expanding and leaf drop occurring. The severity of the disease is directly related to temperature and the amount of rainfall; generally, years with high temperature, abundant rain, and humid conditions see severe incidence. Japanese euonymus leaf spot disease is prone to co-occur with scale insects and aphids, worsening the plant's condition. Extensive management, poor drainage, overly dense planting, and poor ventilation easily lead to disease occurrence.

3. Control measures: Following the principle of "prevention first, combining prevention and control." Start with plant selection, planting, and management to enhance plant disease resistance. When disease occurs, treat early, treat when minor, and treat thoroughly to inhibit its development.

1. Eliminate infection sources: In winter, clear fallen diseased leaves, burn or deep-bury them to eliminate infection sources.

2. When planting and raising seedlings, select healthy plants to improve disease resistance.

3. Strengthen maintenance and management: Choose plots with good drainage and moderate fertility to facilitate plant growth, enhance tree vigor, and improve disease resistance. Plant at a reasonable density, pay attention to ventilation and light penetration, reduce leaf surface humidity, and decrease disease incidence.

4. Chemical control: The early stage of pathogen infection is the best time for control. At this time, chemical treatment of Japanese euonymus can effectively control further disease development. Common chemical agents include Bijunsha 800-1000 times dilution, 75% thiophanate 1500 times dilution, 50% carbendazim and 75% chlorothalonil 500 times dilution. Chemical agents should be used alternately, sprayed once every 7 to 10 days, with 2 to 3 consecutive applications giving good results. In the mid-to-late stage of disease, Penjun 2000-3000 times dilution can be used, sprayed once every 7 to 10 days, with 2 to 3 consecutive applications able to promptly control the disease. Other agents that can also be used include Amistar, kresoxim-methyl, etc.