How should the four common bean diseases be prevented and controlled?

1. Root drowning: Beans prefer moisture and tolerate drought but not waterlogging. Therefore, on the basis of ridge cultivation, small amounts of water should be applied to avoid water accumulation in the field, which prevents the roots from breathing and causes plant death.

Control measures: Avoid flood irrigation. If there is heavy rain, drain the water promptly. After the weather clears, if conditions permit, appropriate shallow hoeing can be done to increase soil permeability and improve root vitality.

2. Phytophthora blight mainly damages the stems and vines, and sometimes the leaves and pods are also affected. It constricts at the base of the stem, causing the upper part to wilt and die. When humidity is high, white mycelium is produced on the diseased part. It usually occurs easily when ventilation is poor and soil humidity is high.

Control measures: Spray with 72% DuPont Curzate at 500 times dilution or 72.2% Previcur at 800 times dilution, or spray with 69% Anke Mancozeb at 1000 times dilution. Apply once every 7 to 10 days, for 2 to 3 consecutive sprays.

3. Fusarium wilt: The pathogen mostly invades through fine roots. The leaves of diseased plants turn yellow from bottom to top and fall off easily. Cracks sometimes appear on the root and stem base. Finally, the plant wilts and dies. When the diseased part is cut open, the vascular bundles can be seen turning brown, and in severe cases the exterior also turns brown. When humidity is high, a pink mold layer is produced. This disease is mostly caused by continuous cropping or high humidity in the greenhouse.

Control measures: The most effective method is to apply 50% DT at 500 times dilution mixed with 20% Tolclofos-methyl at 1000 times dilution as a root drench before the disease occurs or in the early stage of the disease, once every 7 to 10 days, for 2 to 3 consecutive applications. Be sure to prevent and treat early.

4. Root rot: The leaves of diseased plants turn yellow from top to bottom and wilt. The leaves begin to yellow and wither from the leaf margins and do not fall off easily. Diseased plants are easy to pull out. The stem base and roots are dark brown, the lateral roots fall off, and the main root rots. Finally, the diseased plant dies. In flat-bed planting, with excessive watering, insufficient fertility, and extensive management in continuous cropping land, the disease is severe.

Control measures: In the early stage of the disease, spray or drench with Hymexazol at 1500 times dilution or Root Rot Ling at 300 times dilution. In addition, mix with Fengshou No. 1 at 800 to 1000 times dilution for root drenching, once every 7 to 10 days, for 2 to 3 consecutive applications.