What is the special-effect pesticide for watermelon bacterial leaf blight? Detailed explanation of symptoms and disease patterns

AbstractSpecial-effect pesticides for watermelon bacterial leaf blight: chlorothalonil wettable powder, procymidone wettable powder, mancozeb wettable powder. Main symptoms of watermelon bacterial leaf blight: first, obvious water-soaked small spots appear on the leaf margin on the underside of the leaf, or between the veins; when humidity is high, it causes the leaves to lose water and develop green wilt. Disease pattern of watermelon bacterial leaf blight: the pathogenic bacteria overwinter in the tissues of diseased plant residues or inside seeds, and are mainly spread by insects, invading through wounds.

I. Special-effect pesticides for watermelon bacterial leaf blight

1. After soaking the seeds in 55°C warm water for 15 minutes, then soak the seeds for 2 hours in 75% chlorothalonil wettable powder, or 50% iprodione wettable powder 1000x solution, rinse with clean water, then germinate and sow.

2. Generally in the early stage of disease onset or before rainfall, spray 75% chlorothalonil wettable powder 500-600x solution, 50% iprodione wettable powder 1000x solution; after disease onset or when humidity is high, spray 80% Daconil M-45 wettable powder 600x solution.

3. As well as 50% procymidone wettable powder 1500x solution, 70% mancozeb wettable powder 400-500x solution, spraying 60 kg of solution per mu, once every 5-7 days, 3-4 consecutive sprays is sufficient; at the same time, note that re-spraying should be carried out after rain, and water should be drained promptly when there is standing water in the field.

II. Main symptoms of watermelon bacterial leaf blight

1. First, obvious water-soaked small spots appear on the leaf margin on the underside of the leaf, or between the veins; when humidity is high, it causes the leaves to lose water and develop green wilt; when the weather is clear and the temperature is high, it is prone to form 2-3 mm round to nearly round brown spots covering the leaf surface, which later merge into large spots, the diseased parts begin to thin, forming withered leaves.

2. After the stems and vines are infected, spindle-shaped or elliptical slightly sunken brown spots will appear; after the fruit is infected, round brown sunken spots with slightly raised edges will appear on the fruit, which can penetrate deep into the flesh and cause the fruit to rot; when humidity is high, the diseased parts will grow a grayish-black to black mold layer.

III. Disease pattern of watermelon bacterial leaf blight

1. Generally the pathogenic bacteria overwinter in the tissues of diseased plant residues or inside seeds, and are mainly spread by insects, invading through wounds; in continuous cropping land, where the previous crop had severe disease, there is relatively more bacteria stored in the soil; low-lying waterlogged terrain with poor drainage; heavy clay soil that is acidic; excessive application of nitrogen fertilizer; over-dense cultivation with closed plant and row spacing and no ventilation or light penetration; bacteria-carrying seeds, bacteria-carrying nutrient soil used for raising seedlings, organic fertilizer not fully decomposed or bacteria-carrying.

2. As well as rainy early spring or an early plum rain season, warm climate, high air humidity; rainy autumn, heavy fog, heavy dew or an early cold snap; greenhouse cultivation often avoids ventilation to remove moisture in order to keep warm, which easily causes excessive humidity; the occurrence of these conditions will all lead to watermelon developing bacterial leaf blight.