How to prevent and control anthracnose and leaf spot on Japanese euonymus?

Japanese euonymus is commonly used as a hedge in gardens. It is drought-tolerant and tolerates pruning well, and has strong resistance to various toxic gases and smoke and dust. However, the occurrence of anthracnose and leaf spot causes the plants to drop leaves prematurely, or even die, seriously affecting the ornamental effect of Japanese euonymus. The two diseases often occur together, with two types of lesions on the same leaf, but they can be prevented and controlled together.

1. Anthracnose

1. Symptoms The disease occurs on leaves and young shoots. Leaf lesions are elliptical or round, about 3 to 12 mm in diameter. The lesion margins have a relatively narrow dark brown raised edge, and the center is grayish-white. Later, relatively coarse round or elliptical small black spots form in the grayish-white area, sparsely arranged, mostly on the upper surface of the leaves, sometimes arranged in lines. On young shoots, the lesions are elongated, grayish-white, with small black spots on them, and can cause the branches to die. This disease often occurs together with Japanese euonymus leaf spot; the difference is that the lesions of this disease do not have a yellow halo around them.

2. Occurrence pattern The pathogen overwinters as mycelium or acervuli in diseased branches and diseased leaf tissues. In May and June of the following year, when the temperature is suitable, conidia germinate and often invade through wounds on the host. This disease is not strongly parasitic and can only invade through wounds, and its occurrence period is slightly later than that of leaf spot.

2. Leaf spot

1. Symptoms In the early stage of the disease, there are small yellow spots on the leaves, which gradually turn yellowish-brown and expand into round or irregular lesions. The lesion diameter is 2 to 10 mm, and can reach up to 15 mm at most. The lesion margins are raised, and the brown margin is relatively wide. Outside the raised margin, there is also an extended yellow halo. In the later stage, the lesions are grayish-brown or grayish-white, with darker margins, and the center of the lesion is yellowish-brown or dark brown, with small black spots borne on it. In severe cases, the lesions join together into a single patch, and the leaves turn yellow and fall off.

2. Disease pattern The pathogen overwinters as mycelium and other forms on diseased leaves or fallen leaves, and diseased remnant plants serve as latent sites. Spores are spread by wind and rain. In spring of the following year, as the temperature rises, conidia are produced and invade through stomata or pruning cuts and wounds. In the Tianjin area, infection generally begins in June, and July and August are the peak infection period. From mid-August to September, the disease occurs in large amounts. When the disease is severe, the lesions expand and leaf drop occurs. Generally, hot, rainy, humid and moldy climates lead to severe disease. In addition, when plants age, the disease also worsens.

3. Control methods

1. Reduce sources of inoculum Collect diseased branches and fallen leaves in autumn and winter and burn them in a centralized manner.

2. Select healthy seedlings When planting and raising seedlings, choose robust plants to improve disease resistance.

3. Strengthen maintenance and management Plant at a reasonable density, pay attention to ventilation and light transmission, reduce leaf surface humidity, and reduce the chance of disease occurrence.

4. Chemical control In the early stage of the disease, promptly spray Bijunsha at 800-1000 times dilution, or 50% carbendazim at 500 times dilution, or 75% chlorothalonil at 500 times dilution. Plants that have not yet developed the disease should be sprayed for prevention. Chemical agents should be used alternately, sprayed once every 7 to 10 days, for 2 to 3 consecutive times. In areas with severe disease, diseased plants should be removed, and fungicides such as Miaojunling at 200-300 times dilution should be used to drench and disinfect the soil two or three times, and then replant.