needle drop disease of Korean pine

Pinus koraiensis needle drop disease is a common disease in the world. The disease can be infected from young trees to big trees, causing early defoliation of trees, affecting growth, and can lead to the decline and death of diseased plants.

Symptoms: the disease usually harms 2-year-old needles, and some 1-year-old needles can also be damaged. At the initial stage of the disease, there are very small yellow spots or segment spots on the susceptible needles, and the whole leaves turn yellow and fall off in late autumn. In the following spring, the susceptible needles produced large, black or gray, long oval or oval protuberances with paint luster, and there was a longitudinal crack in the center, which was the ascus of the pathogen. Some diseased leaves die and do not fall off, and produce fruiting bodies on them; some needles are only infected and withered in the upper part, but also produce fruiting bodies, and the lower part remains green.

Pathogen: the pathogen is LophodermiummaximumB.Z.HeetYang, which belongs to Ascomycetes subphylum, Arteriacea, Streptomyces, speckle shell fungi.

The regularity of the disease: the pathogen overwintered on the landing needles with hyphae or immature ascomycetes. When the conditions were suitable in the spring of the following year, the ascospores were produced one after another when the ascomycetes matured. In rainy or humid conditions, the ascus disc expands by absorbing water, and the ascospores are emitted from the ascus and spread by means of air flow. Ascospores germinate on needles and form germ tubes, which invade from the host stomata for infection damage. Ascospores can be released from early June to late August, especially in July, so they can be infected many times from spring to summer. Pathogens mainly infect needles for more than 2 years, and needles are sometimes infected in that year. The occurrence of disease is closely related to climatic factors. When the daily average temperature is 25 ℃ and the relative humidity is above 90%, it is most suitable for ascospores to spread and germinate and invade. During the period of ascospore dispersal, if there is continuous overcast and heavy rainfall, it can restrain the spore dispersion. In addition, the occurrence of the disease is closely related to the growth status of trees, all the causes of tree growth decline, can aggravate the occurrence of the disease. There are many reasons for the decline of tree potential, such as dry planting land, too much Rain Water, poor soil, trees suffering from diseases and insect pests, poor tending management and so on. According to foreign reports, the occurrence of pine needle disease is related to air pollution. At present, it is believed that air pollutants affect the soil and climate, which leads to the decline of tree growth, thus leading to the occurrence of the disease.

Control: ① reduces the source of infection: cut down seriously diseased plants, properly trim the bottom branches of diseased trees, remove and burn diseased leaves, so as to reduce the spread of diseases. ② strengthens cultivation management, increases soil fertility and promotes tree growth. ③ medicament prevention and cure: at the initial stage of the disease, spray 1-100 Bordeaux solution, or 65% Dysen zinc 500-fold solution, or 45% Dysenamine 200-300 times solution.