White spots on Shanghai bok choy leaves and brown spots on petioles? Anthracnose control methods

   Shanghai bok choy anthracnose often occurs from June to September. When planting density is too high, the field becomes congested, with poor air circulation, more rain, and easy waterlogging after rain; when fertilizer and water are often lacking, Shanghai bok choy grows poorly and the disease is more severe. Shanghai bok choy anthracnose mainly damages the leaves, and sometimes also the petioles. In the early stage of leaf infection, nearly circular sunken spots with white centers and brown edges appear on the leaves; in the later stage, the spots become white or grayish-white and semi-transparent, and they tend to perforate when the weather is dry. On petioles, the disease often forms long oval or spindle-shaped, yellowish-brown to grayish-brown sunken spots with slightly darker edges, and in the later stage the spots often split open toward both sides.

Shanghai bok choy anthracnose

    Control methods: planting density should be reasonable, fertilizer and water management should be strengthened to promote vigorous growth of Shanghai bok choy, and accumulated water should be drained promptly after rain. After harvest, remove diseased and residual Shanghai bok choy from the field in time, take them out of the field, and destroy them centrally.

    Seed treatment. Use 25% bromothalonil wettable powder or 50% prochloraz-manganese complex wettable powder at 0.3—0.4% of the weight of Shanghai bok choy seeds for seed dressing, or use 2.5% fludioxonil suspension seed coating agent for seed coating.

    In the early stage of the disease, the following fungicides can be used for control: 20% pyraclostrobin water-dispersible granules 1000—1500 times liquid + 80% zineb wettable powder 600—800 times liquid; 20% difenoconazole•prochloraz microemulsion 2500—3500 times liquid; 50% kresoxim-methyl dry suspension 3000 times liquid + 70% propineb wettable powder 600—800 times liquid; 30% benclothiaz emulsion concentrate 1000—1500 times liquid + 70% metiram water for spraying with water, depending on the condition of Shanghai bok choy anthracnose, once every 7—10 days, for 2—3 consecutive times.