We here no matter what variety of potato, adults and children call it yam. Because people here like to eat it very much, so plant a lot. In the past, we used to grow local varieties, which were small, but now we have introduced foreign varieties, which are very big, and the big ones weigh more than one pound. Small, water-soaked, yellowed spots with dark brown to black centers begin to occur on the leaves. The spots on the back of the leaves have a ring of white mold, and in severe cases most of the leaves of the plant plant die, turn black and fall off. When tubers are infected with late blight, they show a slightly pitted, dark-colored spot on the epidermis of the potato.

Early blight mainly occurs in the seedling stage of potato, after the plant grows up there is also damage, mainly harm to the plant stem leaves and stem tuber, leaf blade manifested as the emergence of irregular black-brown concentric whorls, petiole bifurcation place also have black concentric whorls of disease spots. Potato late blight, the early leaves will appear dark small round spots, stalks black, leaf buds dry, in the case of high humidity on the back of the leaf blade, stalks on the junction of the disease will appear gray-white mold layer, in the dry weather when the mold layer is not obvious. Late blight spreads quickly and is harmful to potatoes.

Late blight, late blight is also known as potato plague. Mainly jeopardize the leaf stem tuber, is a disastrous disease of potato. Mainly by poor drainage, field humidity, excessive nitrogen fertilizer application and other circumstances, this disease occurs fast, spread fast, leading to large-scale plant deaths; from the bottom of the leaf to the development of the disease infestation. The first to develop are close to the ground of the leaves, the onset of the leaves turn yellow, branches shriveled and weak, from stem rot until the potato. Prevention and control methods: strengthen ventilation during the growing period, the field can not be too wet, the onset of the disease, can choose Chunrexin, in the biotin, etc. for prevention and control.

Can be used in pharmaceutical control, in the seedling out of the flush, the choice of imidacloprid, once again net two agents, according to the order of leaf stems, back of the leaf, leaf surface alternating spray, every 7 ~ 10 days spraying. It will first from the edge of the potato leaves, into the kind of brown hard lumps, and then in a little bit of spread, until the infringement of the whole potato. These infested leaves will have white spotting symptoms on the reverse side which can be well recognized.