Identification and Control of Black spot of Poplar

Poplar black spot, also known as poplar brown spot, the disease can infect a variety of poplar, seedlings, young trees, big trees can be susceptible, seriously affect the normal growth of trees, resulting in economic losses. Symptoms: it generally occurs on the tender shoots and ears of leaves, spreading from top to bottom, mainly harming the leaves. At the initial stage of the disease, needle-like sunken and shiny spots first appear on the back of the leaves, and then the disease spots expand to about 1 mm, black and slightly raised. Brown spots also appear on the front of the leaves, and milky spots appear in the center of the disease spots (positive and negative sides of the leaves) 5-6 days later, that is, the conidium pile of pathogens. Later, the disease spot expanded and connected into large spots, and most of them became round. When the disease was serious, the whole leaf turned black, and the diseased leaf could fall off early for 2 months. When the seedlings are young, if all the leaves die, it is easy to lead to the death of the plants. if the seedlings become sick when they are unearthed, the leaflets and neck will all turn black and the diseased seedlings will be twisted and not straight. Disease regularity: the pathogen overwintered with mycelium in the disease spot of fallen leaves or branches. The disease began in early May and reached its peak in summer and autumn until the leaves fell, which could harm poplar leaves, petioles, fruit ears, tender shoots, etc., forming angular, nearly round or irregular dark brown spots with a diameter of about 1 mm, some up to 5 mm. Disease spots can be connected into irregular large spots for a long time, causing early defoliation. The new conidia produced by the pathogen spread by the wind in May and June of the following year, fell on the seedling leaves and invaded the leaves through stomata. The disease appeared in 3-4 days, and a conidia disk was formed in 5-6 days for re-infection. Comprehensive control methods: ① to strengthen nursery management. Disease-resistant varieties should be selected for seedling cultivation, attention should be paid to time seedlings, ventilation and light transmission conditions should be improved, field management such as drainage should be done well, disease conditions should be reduced, continuous cropping should be avoided or the nursery should be set up near susceptible plants, and seedlings can be planted in a planned way. Seeds with bacteria need chemical treatment to prevent seedling disease. Dry seeds can be treated with 85% chlorothalonil wettable powder 1000-1500 times or methyl topiramate and duodine powder. Reasonable close planting and timely thinning of ② can keep the forest ventilated and transparent. Clean up the fallen leaves in the forest in time to reduce the source of the disease. During the onset of ③, the nursery and adult forest should be sprayed with 200x Bordeaux solution or 85% mancozeb 250x solution. During the rainy season, 0.3% gelatin (or soybean powder or soybean milk) should be added to the potion to prevent it from being washed away by water, and diseased leaves and fallen leaves should be cleaned at any time to eliminate pathogens. Or 0.3% urea and potassium dihydrogen phosphate mixture.