Ears are prone to disease, generally starting from the tip of the ear near the ground, and the ear axis and small fruit stalks are the most prone to disease. Water-soaked, light brown and irregular rot spots are produced at the initial stage of the disease, then the diseased part gradually loses water and dries up and spreads to the fruit, the fruit stalk turns light brown, then gradually expands into soft rot, and finally the whole fruit turns brown and rots, the fruit shape remains unchanged, and the stalk of the ear shaft often shrinks; After onset 1 week, the fruit surface is covered with a layer of gray spots, which are conidia of pathogenic bacteria. When the disease is serious, the whole ear tends to rot, and when it is shaken, the diseased ear and diseased grain are easy to fall off. Sick fruits give off a special musty smell when they are wet. If the disease occurs before fruit sizing, because of its low sugar content, fruit grains are easy to lose water and dry up, forming dark brown hard fruits, which often hang on trees for a long time. It is easily confused with atrial blight.
The disease of new shoots first occurs at the core picking place and other damaged parts, especially the sprouting branches sprouting from the soil. At the beginning of the disease, the lesion was water-soaked, dirty green or light brown oval, and then the lesion spread to both ends and gradually turned dark brown, with concave lesions and gray-white spots on the surface. Sometimes the epidermis becomes brown, dry, inclined, separated from xylem tissue, and longitudinally cracked and messy. When the disease is serious, it can make the branches and vines die or break, which seriously affects the growth and development of plants.
Leaf diseases mostly occur at leaf edge, tip and damaged parts. At first, dark green to yellowish brown, irregular or nearly round lesions were produced at the leaf edge or tip, and the edge was soaked in water, and then gradually spread to the middle of the leaf, forming a concentric ring with alternating shades. Conidia can also form in wet weather, mostly on both sides of veins. Sick leaves break easily.
Under the condition of open field cultivation, conidia spread to annual branches by rain splashing, wind blowing and insects after rainfall. Conidia germinate when exposed to rain or dew, and invade tissues through wounds or natural orifices for primary infection. After that, the lesion produced conidia and sporangium, which were reinfected repeatedly.
The incidence rate is closely related to temperature, rainfall intensity and rainfall frequency. The more rainfall, the higher the incidence and the more serious the harm. The optimum temperature range for pathogen development is 25 ~ 30℃, and the optimum temperature range for conidia germination is 13 ~ 40℃. Conidia germinate rapidly at 24 ~ 27℃, and when the relative humidity of air is greater than 92%, the lesion expands rapidly. When the air humidity is lower than 92% and the temperature is lower than 23℃ and higher than 36℃, the disease spread slowly.
Results The body position was closely related to the condition. Generally, the closer the ear is to the ground, the more serious the disease is, and the ear more than 50 cm away from the ground has less disease.
Preventive and control measures
(1) Carefully prune, cut off diseased branches, diseased fruit ears and diseased vines, and thoroughly remove burned or buried.
(2) Cleaning the fallen leaves, combining with fertilization, mixing the fallen leaves and topsoil with fertilizer and burying them in the bottom of the fertilization ditch.
(3) Bagging ears to eliminate the harm of germs to ears.
(4) Chemical control: refer to the control measures of grape downy mildew and anthracnose.