Identification and control of common wilt disease in pepper

Capsicum Blight

I. Symptoms: At the early stage of the disease, the top leaves of the plant begin to wilt and droop. Then, the lower leaves start to wilt, followed by the middle leaves. In some cases, one side of the leaves wilts first, or all the leaves wilt at once. During the initial phase, the affected plants show wilting during the day but recover at night. After 2-3 days, the entire plant dies from wilting, with the dead plants remaining green. The roots of the diseased plants often turn brown and rot. The surface of the stem becomes rough, and adventitious roots proliferate on the root area. Some diseased stems may show 1-2 cm brown spots. The xylem of the stalks is visible, and when the stem is cut crosswise, it appears moist, with white, turbid mucus oozing out when pressed.

II. Disease Incidence: Pepper bacterial wilt, also known as pepper vascular wilt, typically does not occur in the seedling stage. It usually appears after the plant starts fruiting, and it is most severe in summer. This is a typical bacterial soil-borne vascular disease. High temperature and humidity, especially after prolonged rain or heavy rainfall, can promote the spread of this disease, leading to outbreaks.

III. Prevention and Control Methods

　　1. Implement crop rotation for 4-5 years, avoiding planting with Solanaceae and legume crops. If conditions allow, implement water-drought rotation, which is the most effective measure to prevent this disease.

　　2. Apply lime or wood ash when preparing the field, create high ridges and deep ditches in the field, and use small amounts of water during irrigation.

　　3. Before the onset of the disease (usually at the early fruiting stage), spray 70% copper sulfate solution at 500 times dilution, or 50% copper oxychloride (DT) wettable powder at 500 times dilution, or 50% spring copper oxychloride (Chunleimycin + copper oxychloride) (DTM) at 500-600 times, or 14% copper ammonia complex agent at 300 times, or 77% mancozeb WP at 500 times. Spray every 7-10 days, and repeat 2-3 times if necessary.

　　4. When sporadic diseased plants are found in the field, remove them immediately and disinfect the infected areas with 2% formalin solution or 20% lime water to prevent the spread of soil bacteria.

　　5. Spray 1:1:240 Bordeaux mixture or 100-150 mg/kg agricultural streptomycin at the early stage of the disease or after heavy rain. Spray every 7-10 days, and repeat 3-4 times for better control.

　　6. When the disease occurs in the field, irrigate the roots with one of the following agents: 10-200 mg/kg agricultural streptomycin, or 40% bactericidal wettable powder at 5000 times dilution, 0.25-0.5 kg per solution. Irrigate once every 10-15 days, up to 3-5 times. At the same time, combine root irrigation with foliar spraying. Use 72% agricultural streptomycin WP at 2000 times, or 14% lycopene copper solution at 300 times, or 77% mancozeb WP at 500 times, or 50% copper amide adipic acid at 500 times, or 50% wettable powder DTM at 500 times. Spray every 7-10 days, repeating 2-3 times.

Pepper Root Rot

I. Symptoms: The upper part of the plant shows obvious symptoms during the flowering stage. Leaves gradually turn yellow and wither from the bottom upwards. In severe cases, the stems and leaves die, while the leaves do not fall off. The main roots and lateral roots become rotten, and no new lateral roots are produced. Under wet conditions, a pink mold appears on the base of the stem.

II. Disease Incidence: The bacteria can survive in the soil for over 10 years, mainly spreading through rain, irrigation water, unfertilized farmyard manure, and agricultural tools. They infect the cortex of the main root and the stem below the surface. High temperature and humidity, poor drainage, undecomposed base fertilizer, and long-term continuous cropping are key factors contributing to this disease.

　　1. Implement a 2-5 year crop rotation; use high ridge cultivation to reduce soil moisture; clear ditches and drain water after rain, and promptly remove diseased plants.

　　2. When planting, soak the roots in anti-dry spirit wettable powder at 600 times dilution or toxic poison at 3000 times dilution for 10-15 minutes after transplanting. Alternatively, mix 1 bag of 150 raw antibacterial powder with 0.5 kg of rice bran (without water), soak the roots of pepper seedlings, and transplant them. Add 1.5-2 kg of copper sulfate per acre when watering after planting.

　　3. After planting, spray Huanmiao perfusion at 3000 times, 600 times, or anti-dry Ling, each at 250 ml, once every 7 days, up to 3 times. If the disease is cured, increase the dose accordingly.

Capsicum Blight

I. Symptoms: More common during the flowering and fruiting stages. Initially, the lower leaves of the plant wilt and droop, and the whole plant appears to wilt from bottom to top. Mildly affected plants wilt during midday on sunny days but return to normal in the morning and evening or on cloudy days. After several days, the diseased plants turn yellow and die, with severe cases resulting in complete death. The internal tissues of the roots and necks of the plants become brown, and the bark easily falls off. For example, cutting a small section of the diseased stem and placing it in a test tube with fresh water will not produce any white pus (this helps distinguish it from bacterial wilt).

II. Disease Incidence: The bacteria overwinter on infected plant material and can survive in the soil for many years. The disease is more severe during rainy periods in summer, and it develops rapidly after rain. It thrives in wet, heavy, slightly acidic soils with poor drainage, continuous cropping, and excessive nitrogen fertilizer application. High temperature and humidity environments further exacerbate the disease. The presence of root-knot nematodes in the soil can worsen the condition.

　　1. Combine with pepper root rot prevention measures.

　　2. Before planting, disinfect the soil with Kekesong wettable agent at 1000 times dilution. Transplant using Dixon at 800 times or anti-dry spirit WP at 600 times solution, soaking the roots for 10-15 minutes after transplanting. Alternatively, mix 1 capsule of 150 antibacterial powder with 0.5 kg of rice bran (without adding water), soak the roots of the pepper seedlings, and dip the roots. Add 1.5-2.0 kg of copper sulfate per acre when watering after planting.

　　3. Spray 50% carbendazim WP at 500 times dilution, or 40% polysulfur suspension at 600 times, or 50% succinic acid copper WP at 400 times. These solutions can be applied at the beginning of the disease. Alternatively, use anti-dry wettable powder at 1000 times for spraying or 600 times for root irrigation, applying 0.5 liters per plant during rooting. Repeat 2-3 times for optimal results.

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