Some leaves under tomato seedlings turned yellow.

There may be tomato Fusarium wilt, also known as Fusarium wilt, prevention and control methods:

(1) seeds. Collect seeds in disease-free land or disease-free plants to prevent them from carrying bacteria. Seeds with bacteria can be soaked in 500 times of 50% carbendazim 1 hour for disinfection, and then washed to accelerate germination.

② rotate. Rotation with non-solanaceae vegetables for more than 5 years, rotation with rice only takes 1 year.

③ Soil improvement. When the acid soil is ploughed, 750 ~ 1500 kg lime powder is added to each hectare, which is adjusted to be slightly alkaline to inhibit the growth of bacteria.

④ Seedling raising. Select a new aseptic seedbed to raise seedlings. If the old seedbed can be disinfected by chemical agents, use 8 grams of 50% carbendazim per square meter, add 10 ~ 15 kilograms of fine soil, mix well, apply 1/3 medicinal soil to the seedbed, and 2/3 medicinal soil will be used as covering soil.

⑤ Field management. At the same time of applying sufficient organic fertilizer, increase phosphorus and potassium fertilizer, strengthen field management and improve plant disease resistance. Clean up the diseased plant residues in time and take them out of the field for burial or incineration.

⑥ Chemical control. At the beginning of the disease, 500 times of 50% carbendazim and 200-300 times of 10% shuangxiaoling were used. One of the above drugs, each plant is infused with 0.25 kg of liquid, 10 times a day for 2-3 times continuously.