Occurrence Patterns and Control Techniques of Sweet (Hot) Pepper Viral Disease

Viral disease is a major disease in the production of sweet (hot) peppers. Early onset affects the normal growth of plants, forming a "little old man" appearance; late onset causes mosaic leaves and mottled fruit, affecting photosynthesis and marketability, often causing significant economic losses.

To help farmers solve this problem, Tunliu County, through 3 years of research and experimental demonstrations, has preliminarily explored some effective integrated control measures. The details are as follows:

I. Symptoms:

The main symptoms are mosaic, malformation and clustering, and necrotic streak, 3 types. Mosaic: diseased leaves show mottling of dark green and light green, leaves wrinkle, are prone to brittle cracking, or produce brown necrotic spots. Leaf malformation and clustering: at early onset, the veins of the heart leaves fade green, gradually forming mottling of alternating dark and light, leaves wrinkle and thicken, and produce large yellowish-brown necrotic spots. Leaf margins curl upward, young leaves are narrow and thread-like, diseased plants are obviously stunted, and the upper leaves are clustered. When fruit is infected, it becomes mottled like a painted face with alternating dark and light, forming brown necrotic spots; the disease spreads along the petiole to the branches, main stem, and growing point, producing systemic necrotic streaks, plants are obviously stunted, causing leaf drop, flower drop, and fruit drop.

1. Pathogens:

The main pathogens of sweet (hot) pepper viral disease are: Cucumber Mosaic Virus (CMA) and Tobacco Mosaic Virus (TMV). Cucumber Mosaic Virus causes systemic mosaic, malformation, clustering, and fern leaf, with necrotic spots and streaks appearing on leaves. Tobacco Mosaic Virus mainly damages in the early stage, often causing acute necrotic spots or vein necrosis and top necrosis.

III. Occurrence Characteristics:

Viral disease is mainly transmitted in two ways: insect transmission and contact transmission. Insect vectors include aphids, thrips, planthoppers, etc., and the virus they transmit is Cucumber Mosaic Virus. Virus-carrying insects acquire the virus from surrounding weeds and transmit it by piercing and sucking on sweet (hot) peppers. The virus transmitted by contact infection is Tobacco Mosaic Virus, spread through contact and friction during agricultural activities such as seedling separation, pruning, and management. Continuous cropping, low-lying terrain, lack of fertilizer, lack of water, weak crop growth, and high temperatures all favor the occurrence of viral disease.

IV. Control Measures:

1. Select disease-resistant varieties: such as Beijing Zhongjiao No. 4, Xiangyan No. 16, Super Green Ba No. 16, Bingfeng 207, Nongyan 16-2, etc., which are relatively resistant and tolerant to disease.

2. Agricultural management measures: (1) Crop rotation. This can effectively reduce infection opportunities. (2) Intercropping with tall crops. For example, intercropping with corn can provide shade and lower temperature, reducing the incidence of viral disease, phytophthora blight, and sunscald. (3) Clean the field and deep plow in autumn. Do not casually discard diseased fruit and leaves; take them out of the field, burn or bury them. Autumn plowing depth should be more than 15 cm, turning diseased residues into the soil.

3. Cultivate strong seedlings: ① Sun-dry seeds. Sun-dry seeds in sunlight for 2-3 days to remove pathogens on the seed coat; ② Soak seeds. Put the sun-dried seeds into a container, add 25°C hot water, and soak for 3-4 hours; ③ Hot water soaking. Use another container, put the soaked seeds in, first add cold water, then add 25°C hot water, raise the temperature to 55°C for half an hour, then let it cool naturally; ④ Chemical treatment. Soak seeds in 10% trisodium phosphate for 10 minutes, then rinse clean with clean water; ⑤ Germination. Sowing dry seeds takes more than 20 days to emerge, but after germination, seedlings emerge in 7-8 days; ⑥ Seedbed soil treatment. Before sowing, on the seedbed, use 9 grams of carbendazim per square meter mixed into 5 kg of soil. Place the toxic soil layer below and cover above; at this time the seedbed temperature should be controlled at 25°C-30°C. Pay attention to covering soil: too thick, seedlings are weak; too thin, seedlings emerge with seed coats attached. Keep it at a thickness of 1 cm. After emergence, control the seedbed temperature at 25°C-28°C. When 2 leaf branches come out, the growing point begins to grow; this period is called the heart-breaking stage, and it is also the most fragile time, prone to damping-off disease. Spray with Previcur or Kexiu 1-2 times.

4. Determine the planting period: Green peppers are both warmth-loving crops but also afraid of high heat, so they should be planted at the right time. Too early makes old seedlings likely; too late, the ridges cannot close, causing high soil temperature, root damage, water unable to rise, and susceptibility to disease. After planting, to promote rapid recovery and early development, spray a growth regulator once; with or without spraying, the growth period differs by about 10 days.

5. Reasonable watering: Green peppers like water but are also afraid of water. Too much watering causes root retention, weak absorption, and decline, so water frequently with small amounts, level the ground, and have matching canal systems.

6. Reasonable fertilization: Advocate balanced fertilization. The fertilizer ratio required by green peppers is: N:P:K=1:0.5:1.2-1.4. In the later stage, potassium fertilizer must be increased to improve plant stress resistance.

7. Physical control: Use insect-proof nets to prevent transmission vectors such as aphids and planthoppers, which can greatly reduce the incidence of viral disease.

8. Chemical control: The agents used include: ① Moroxydine hydrochloride, trade names: Virus A, Dukexing, Bingduxianfeng, Bingdusuke; ② Mushroom polysaccharide, trade names: Junduning, Kangfengsu, Kangdufeng, Kangfengji No. 1, Bingduheishashou; ③ Zhibingling. When the disease is mild, choose any one for spraying; if the occurrence is severe, accounting for 20%-30%, the three agents must be mixed together and sprayed at the same time, achieving "drenching," once every three days, spraying three times consecutively.