Anthracnose is a common disease on peppers, especially in the middle and late stages of pepper growth. If there is hot and humid weather, the chance of disease is very high. Once the disease occurs, it spreads quickly and lasts for a long time, causing the stems to crack, leaves to fall early, and the fruit to lose its commercial value. In mild cases, the loss can reach 20%-30%. In epidemic years, the yield reduction is at least 50%, and it may even cause a total crop failure.
1. Harm characteristics
Pepper anthracnose mainly harms fruits and leaves, and can also infect stems and fruit stalks. Fruits and old leaves are the most seriously affected.
(1) Fruit infection. When the fruit is infected, moist, yellow-brown oval or irregular lesions appear at first, slightly concave, with concentric rings on the surface. There are many orange-red small particles on the rings, which later turn into black dots. When the weather is humid, light pink granular viscous substances may overflow. When the weather is dry, the diseased part shrinks, becomes thin and paper-like and easy to break.
(2) Leaf infection. After the leaves are infected, water-soaked chlorotic spots with concentric rings will appear at first. They will become larger and turn brown, with the middle part being lighter in color. There will be many small spots on the spots. As the disease progresses, these small spots will slowly merge together to form an irregular large spot. If the weather is dry, it is easy to crack, and in severe cases, it can cause leaf fall.
(3) Stems and fruit stalks are infected. After the stems and fruit stalks are infected, irregular short strips of sunken brown spots will appear at first. There are also concentric rings on the spots, which are slightly sunken. When wet, pink substances will flow out of the surface of the spots. When dry, the stems and fruit stalks are easy to crack.
2. Occurrence pattern
(1) Pathogens. The pathogens of pepper anthracnose are Colletotrichum oxysporum, Colletotrichum nigrosporum and Colletotrichum gloeosporum. They can infect pepper fruits at all stages of development, but symptoms usually appear on fruits that are about to mature.
The pathogen can be spread through wind and rain, insects, irrigation and agricultural operations. The pathogen has a wide host range and can survive the winter on diseased remains or crop seeds (which is also the main source of initial infection), or on weeds, other crops or in the soil.
(2) Infection process. The pathogen will infect under warm and humid conditions. The temperature range for pathogen development is 12-33℃. When the relative humidity is greater than 80%, especially when the disease resistance of mature plants is poor, it is most suitable for disease and infection.
The disease can occur 3 days after the pathogen invades. First, small, slightly concave, dark yellow spots will form on the surface of the pepper fruit. When the humidity is high, the spots will darken and expand together. The pathogen will form pink spores arranged in a ring on the spots, and turn into small black spots as the disease progresses.
After the pepper fruit is infected by anthrax, it is usually infected by other pathogens, resulting in complex infection. After the initial infection, a large number of new conidia grow, which can re-infect after spreading.
(3) Occurrence pattern. Low-lying terrain, heavy soil, poor drainage, dense planting with poor permeability, insufficient fertilization or excessive nitrogen fertilizer, rough management causing surface wounds, or leaf spot disease causing many leaves to fall, and fruits exposed to the sun, etc., are all prone to induce anthracnose, which will aggravate the infection and spread of the disease.
Sweet peppers are more susceptible to the disease than hot peppers. Continuous drizzle, heavy fog, and dewy weather are prone to cause the disease to spread.
3. Prevention and control methods
(1) Seed treatment. Choose highly resistant varieties and soak the seeds in warm water or with chemicals. The chemicals can be soaked in 1% copper sulfate for 5 minutes, or soaked in 500 times diluted 50% carbendazim wettable powder for 1 hour, or mixed with 50% thiram wettable powder, with the dosage being 0.4% of the seed volume.
(2) Cultivation and management. Take measures to drain water before planting or before transplanting. When transplanting, choose strong seedlings, plant them at a reasonable density, avoid continuous cropping, and apply phosphorus and potassium fertilizers appropriately to promote the growth of strong plants and improve disease resistance. The pepper anthracnose pathogen is a weak parasite. Mature, aging, and injured fruits are prone to disease. Timely fruit picking can reduce the chance of disease. After the fruit is harvested, the diseased fruits and diseased remains left in the field should be completely removed and taken out of the field for centralized burning or deep burial.
(3) Chemical control. When peppers enter the flowering and fruiting period, chemical prevention can be carried out in advance. You can choose 600-800 times diluted 70% methyl thiophanate wettable powder or 500 times diluted 80% mancozeb wettable powder for continuous control 2-3 times.
