1. Anthracnose is one of the possible reasons. Anthracnose can cause round or irregular lesions on leaves, with gray center and brown edges, and small black spots on the lesions, which will gradually spread outward. The control methods include using 42.8% fludioxime 1500 times solution, 10% difenoconazole 1500 times solution, 25% pyraclostrobin 1500 times solution, 75% tebuconazole 4000/6000 times solution and 45% tebuconazole.
2. Leaf spot disease is also one of the causes of this symptom. Leaf spot will lead to the formation of round or irregular spots with a diameter of 2- 12 mm, which are light brown or yellowish brown, and gray-black to nearly black fluff will appear when humidity is high. The control method includes using 500-600 times solution of 75% chlorothalonil wettable powder, 50% polysulfide suspension or 500 times solution of 36% thiophanate-methyl suspension.
3. Small spots on pepper leaves may also be caused by virus infection. In this case, the spots on the leaves usually appear at the top or bottom of the leaves and will spread outward. In addition, the leaves may be deformed, affecting the overall growth of plants.
4. Fungal infection is also one of the possible reasons. They usually form round or irregular black spots on leaves, and gradually spread outward, eventually leading to leaf withering and death. In this case, it is usually necessary to use fungicides for treatment.
5. Excessive halothane may also cause spots on leaves. In this case, the spots on the leaves usually appear white or silver and spread to the edge of the leaves. This problem can be solved by reducing irrigation water and adding phosphate fertilizer to plants.
In order to accurately diagnose and effectively treat this symptom, it is recommended that you consult a professional botanist or agronomist.