Downy mildew, the key damage to leaves. The lesion spreads from the bottom of the plant to the top. The lesion was light yellow at first, but irregular after increasing, and the edge was not obvious, resulting in gray mold layer on the lesion on the back of leaves. When it is serious, the lesions are connected with each other and turn brown in the middle and late stage. When the humidity is high, it will turn brown and rot. If it is serious, the whole leaf will turn yellow and wither.

prevention and treatment methods: at the early stage of the disease, azoxystrobin, mancozeb, cymoxanil, fosfom, fosfom, fosfom, metsulfuron and mancozeb can be selected. Spray with water once every 7-1 days depending on the illness. When the disease is widespread, propamocarb hydrochloride, flupirimipram, pyraclostrobin, propamocarb foscarnet, dimethomorph mancozeb, etc. can be selected and sprayed with water once every 5-7 days depending on the disease.

virus disease, which occurs in the seedling stage, mainly shows bright veins or yellow-green patterns on the heart leaves, and then turns into light green and dense flower leaves. Illness in the adult stage is mainly manifested in the shrinking of flower leaves or heart leaves, the yellow leaves wither and fall off in advance or the plants curl into spheres. Prevention and treatment: Before the onset of the disease to the early stage of the disease, ningnanmycin, pyrimidicin, moroxydine hydrochloride, copper acetate and other sprayers can be selected and sprayed once every 5-7 days according to the illness.

Downy mildew, when the disease is serious, pull out the plants and look at the roots, which shows that the fleshy roots are shrunk and deformed, and there are many tumor-like roots on them. The upper part of the ground shows poor growth and development, short height, loss of green and withering, as if lacking liquid fertilizer or withering, and plants wither when it is more serious. Prevention and control methods: ciliates are produced during the growth and development of broccoli, and abamectin can be used to irrigate the roots, and the cultivation techniques can be improved.

Stem blight causes spindle-shaped to irregular dark gray stripes on the stem in the early stage of the disease, and the edge of the lesion is dark brown, and the gray-black spots are often smaller in the middle and late stage. When the disease is more serious, the diseased spot surrounds the stem for a week, causing the diseased part to wither. Prevention and treatment: In the early stage of the disease, azoxystrobin, basic copper sulfate, cuprous oxide and quinconazole can be selected and sprayed with water once every 7-1 days according to the disease condition.