Tomato bacterial wilt is a sudden and severe disease that thrives in hot and humid summer conditions. It mainly affects tomato cultivation in greenhouses during the extended autumn or winter seasons. The disease can cause significant damage if not managed properly.
(1) Symptoms: Although infections may occur during the seedling stage, symptoms are typically not visible at this point. As the plant reaches the early fruiting stage, the top, middle, and lower leaves of infected plants begin to wilt, especially during midday. However, they often recover by evening. If the soil becomes dry and temperatures rise after infection, the plant may die within a few days. The wilting period is usually short, and when the plant dies, it remains green with only slightly lighter leaf color, which is why it's called "green wilt." The roots, particularly the smaller lateral roots, turn brown and decay. Cutting the base of the stem reveals a brown discoloration of the vascular bundle. When squeezed, a cloudy mucus is released from the cut area.
(2) Pathogens and Conditions: Tomato bacterial wilt is caused by the bacterium *Pseudomonas aeruginosa*, which infects the vascular system of the plant. The bacteria overwinter in the soil and can survive for about 14 months. They spread through rain, irrigation, farming tools, and human activities. The bacteria enter the plant through wounds in the roots or stem base, multiply within the vascular bundles, and block the water-conducting vessels, leading to wilting and dehydration. High temperatures and humidity favor the development of the disease. Other factors such as weak seedlings, continuous cropping, poor root health, low-lying fields, excessive watering, and uneven moisture levels can also increase the risk of infection.
(3) Control Measures: 1. Choose resistant tomato varieties. 2. Cultivate strong seedlings or use grafted seedlings, with wild tomatoes like CH-Z-26 serving as a suitable rootstock. 3. Provide shade to seedlings during summer and autumn. 4. Chemical control: During the early stages of the disease, apply 50% iprodione wettable powder diluted 800–1000 times, or 72% agricultural streptomycin soluble powder diluted 4000 times, 50% DT wettable powder diluted 400 times, or 25% copper oxychloride solution diluted 500 times. Apply the solution every 3–5 days for 2–3 applications, and even fill the irrigation system up to three times if necessary.
By implementing these measures, growers can effectively reduce the impact of tomato bacterial wilt and protect their crops. Proper management and timely intervention are key to preventing the spread of the disease.
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