What is pepper anthracnose?

Anthracnose of hot (sweet) peppers mainly harms fruits and leaves, and can also infect stems. When leaves are infected, they initially appear as water-soaked faded green spots, which gradually turn brown. The lesions are nearly circular, grayish white in the middle, with small black dots on the upper part. When the lesions expand, they become irregular in shape with concentric rings, and the leaves are easy to fall off. When fruits are infected, they initially appear as water-soaked yellow-brown lesions, which expand to oblong or irregular shapes. The lesions are sunken, with concentric rings on the upper part, reddish-brown edges, grayish-brown in the middle, and black dots on the upper part. When wet, red sticky substances appear on the lesions, and when dry, they become film-like and easy to break.

Anthracnose of hot (sweet) peppers is caused by infection by fungi of the subphylum Ascomycota and the genus Acanthosporium. The pathogen overwinters as conidia attached to the surface of seeds, or as mycelium lurking inside seeds. It can also overwinter as mycelium, conidia or conidia disks in diseased remains or soil. When conditions are suitable, it can be spread by wind, rain, irrigation, insects and agricultural activities, and seeds can be spread directly. The temperature range for the development of the pathogen is 12-33℃, and the optimum temperature is 27℃. When the relative humidity of the air is above 95%, it is most suitable for disease and infection. When the relative humidity of the air is below 70%, it is difficult to develop the disease. Low-lying terrain, poor drainage, excessive density, excessive use of nitrogen fertilizers, and serious insect pests will aggravate the infection and prevalence of the disease.

2. Biological characteristics of pests

Pathogen: For the pathogen of pepper anthracnose, the predecessors recorded two straight spore groups of anthracnose fungi (Colletotrichum nigrum Ell. et Halst) and (Gloeosporium piperatum) Ell. et Ev. according to the presence or absence of bristles on the conidia. Von Arx (1957, 1970) systematically studied the taxonomy of anthracnose fungi and proposed that the presence or absence of bristles is not a stable trait and cannot be used as a classification feature. Colletotrichum is the only legitimate genus name, called Anthrax, belonging to the order Melanosporales of the subphylum Ascomycota. The above two species are classified as two isolated lines of pepper anthracnose fungi into C. gloeosporioides (Penz.) Sacc.

1. Black anthracnose: The pathogen is Colletotrichum gloeosporioides (Penz.) Sacc., synonym: C. nigrum Ell. et Halst. The conidiophore has dark brown bristles around the edge, with 2 to 4 septa, and is 74 to 128 μm × 3 to 5 μm in size. The conidiophore is short cylindrical, colorless, monospore, and is 11 to 16 μm × 3 to 4 μm in size. The conidia are oblong, colorless, monospore, and 14 to 25 μm × 3 to 5 μm.

2. Red Anthracnose: The pathogen is Colletotrichum gloeosporioides (Penz.) Sacc. (synonym: G.piperatum Ell. et Ev.). The conidia have no bristles, and the conidia are oval, colorless, and monospore, with a size of 12.5-15.7 μm × 3.8-5.8 μm. The sexual stage is Glomerella cingulata (Stonem.) Spauld. et Schrenk].

3. Black spot anthracnose: The pathogen is pepper anthracnose (C. capsici, synonym: pepper thorn disc fungus (Vermicularia capsici Syd.). The conidiophores are densely covered with thick bristles around and inside, especially inside. The bristles are dark brown or brown, with septa, and the size is 95-216μm×5-7.5μm. Conidia are crescent-shaped, colorless, monospore, and the size is 23.7-26μm×2.5-5μm.

Prevention and control measures for pepper anthracnose

Disease control measures: The primary source of infection for pepper anthracnose is the pathogen carried on overwintering diseased remains and seeds. Therefore, good seed treatment, thorough removal of diseased remains, and reasonable crop rotation are effective measures to control the occurrence of the disease.

1. Plant disease-resistant varieties: Develop and utilize disease-resistant resources and cultivate new disease-resistant and high-yield varieties. Generally, varieties with strong spicy flavor are more disease-resistant and can be selected according to local conditions.

2. Select sterile seeds and seed treatment: Harvest seeds from disease-free fruits as sowing materials. If the seeds are suspected of being contaminated, soak them in 55℃ warm water for 10 minutes, or soak them in 70% mancozeb or 50% carbendazim solution with a concentration of 1000mg/kg for 2 hours for seed treatment.

3. Strengthen cultivation management: Plant peppers at a reasonable density so that the rows are not shaded and the fruits are not exposed after the rows are closed; avoid continuous cropping. In areas where the disease is serious, rotate with melons and legumes for 2 to 3 years; apply phosphorus and potassium fertilizers appropriately to promote the growth of strong plants and improve disease resistance; in low-lying wetland planting, ditches and drainage should be done to prevent water accumulation in the fields to reduce the incidence of the disease; harvest fruits in time. The pepper anthracnose bacteria is a weak parasite. Mature, aged and injured fruits are prone to the disease. Harvesting fruits in time can avoid the disease.

4. Clean the fields: After the fruits are harvested, remove the diseased fruits and diseased remains left in the field, burn them or bury them deeply, and carry out deep plowing to turn the surface soil with bacteria to a deeper layer to kill the bacteria. This can reduce the initial infection source and control the spread of the disease.

5. In terms of chemical control, the soil should be disinfected before planting, combined with tillage, spray 50 kg of 3000 times 96% Tianda Methacin solution per 667 m2, or spread 2.5 kg of 70% Dichlorvos wettable powder, or 2.5 kg of 70% Metalaxyl mancozeb per 667 m2 to kill residual pathogens in the soil.

After planting, spray 1:1:200 times Bordeaux liquid every 10-15 days to protect against disease (note! Do not spray open buds and growth points). Spray 600-1000 times melon and solanum professional Tianda-2116 (or 5000 times Kangkai, or 5000 times brassinolide) between every 2 Bordeaux liquid sprays, alternately spray with Bordeaux liquid.