Control methods and pesticides for common grape diseases such as powdery mildew, white rot and anthracnose
Grapes occupy an important position in world fruit production, and grape diseases and pests have a great impact on the growth and development, yield and quality of grape plants.So what are the control methods for common grape diseases such as powdery mildew, white rot and anthracnose? What pesticides are good to use?
What are the control methods for common grape diseases such as powdery mildew, white rot and anthracnose? What pesticides are good to use?
1. Grape downy mildew:
When leaves are infected, irregular pale yellow semi-transparent oil-soaked small spots appear on the upper surface, gradually expanding and turning yellow-green, with indistinct margins, mostly several small spots joining into one irregular or angular large lesion, and on the underside of the leaf a yellow-white downy mold layer is produced, namely the pathogen's sporangiophores and sporangia; in the later stage the lesion turns pale brown, dry-cracks, scorches and curls, and in severe cases the leaves fall off.
Control methods:
Grape downy mildew: before onset, spray Kejia once about every 10 days for protection. After onset, immediately spray 96% dimethomorph technical powder at 1500 times + Lvdasheng at 600 times, or Kejia at 1000 times + 96% dimethomorph technical powder at 2000 times as therapeutic agents, alternating sprays 2—3 times to control the damage, then use 80% Lvdasheng at 600—800 times as a protective agent in rotation for control, and it can also control other diseases occurring at the same time.
2. Grape powdery mildew:
The pathogen mainly infects the green parts of grapes such as leaves, new shoots and fruit clusters. Mature organs do not develop the disease. Leaves first produce gray-white powdery matter on the surface, namely the pathogen's mycelium and conidia. In severe cases the whole leaf is covered with white powdery matter, causing much curling, withering and falling off. Sometimes small black dots are produced, which are the cleistothecia of the spores. Under the powdery patches the leaf surface shows brown mottling, and in severe cases the whole leaf scorches. After fruit is infected, the fruit surface is first covered with white powdery matter; after the powder is removed from the lesions, brown starburst-like patterns appear, and the epidermal cells die. The fruit stops growing, sometimes becomes deformed, and tastes sour; when the fruit has grown larger and is infected in rainy weather, the diseased parts crack and then rot. On fruit stalks and new shoots, gray-white powdery patches first appear on the surface, and later snowflake-like or irregular brown patches form beneath the powdery patches, making the rachis and fruit stalks brittle; the canes cannot mature well, affecting fruit quality and yield.
Control methods:
Grape powdery mildew: eliminate the pathogen; during winter and summer pruning, take care to collect diseased branches, diseased leaves and diseased fruits and bury them deeply in a centralized manner. Strengthen fertilizer and water management during the growing period, pay attention to drainage and waterlogging prevention during the rainy season, spray potassium dihydrogen phosphate and apply compound fertilizer to the roots to strengthen tree vigor and improve disease resistance, and promptly pinch the tips, tie the vines and remove secondary shoots to improve ventilation and light penetration and reduce disease occurrence. For chemical control, before the grape buds swell but before they sprout, spray 3~50 lime sulfur mixture to thoroughly eliminate the overwintering pathogen. After grapes sprout and shoots grow, spray 800 times Lvdasheng solution to prevent the occurrence of various diseases; at the early stage of disease, spray Lvdasheng at 600 times + benzi at 1000 times, or Lvdasheng at 800 times + Baijin or Wansheng No.1 at 800 times, generally spraying once about every 10 days, 3 consecutive sprays, alternating the pesticides, and control can be achieved.
3. Grape white rot:
The pathogen is called Coniella diplodiella, a fungus of the subdivision Deuteromycotina. Grape white rot mainly damages fruit clusters and branch tips; fruit clusters near the ground develop the disease first, and affected clusters first form light brown water-soaked spots on the fruit stalks or rachis, gradually expanding and becoming dry and withered. When fruit is infected, light brown water-soaked rot first appears, then rapidly spreads to the whole fruit, and the fruit stalks dry up and constrict. One week after infection the fruit turns dark brown, with dense gray-white small granular dots under the fruit skin; the diseased fruit loses water, shrinks and becomes a dark brown mummified fruit, and in severe cases the whole cluster rots. After being shaken, diseased fruit easily falls off, and dried mummified fruit clusters often hang on the branches.
Control methods:
Grape white rot: Lvdasheng (25g) + Xinsheng (5g)/Yingde (10ml) + Shize (10g)/(Xianlang 5ml).
4. Grape gray mold:
Symptoms are that when inflorescences and young fruit are infected, light brown water-soaked lesions first appear on pedicels and small fruit stalks or the rachis, then the lesions turn brown and soft-rot; when the air is humid, mouse-gray moldy matter, namely the pathogen's conidiophores and conidia, can be produced on the lesions. When the air is dry, infected inflorescences and young fruit gradually lose water, shrink, then dry up and fall off, causing a large amount of flower and fruit drop, and in severe cases the entire cluster may fall completely. When new shoots and young leaves are infected, light brown or reddish-brown irregular lesions are produced, mostly occurring near the veins; on leaves, indistinct concentric rings sometimes appear, and in the later stage when the air is humid a gray mold layer may also appear on the lesions. Non-lignified new shoots develop the disease in the later part of the growing season, the bark turns bleached white, with black sclerotia or gray mycelial blocks forming spores. When fruit is infected after veraison, brown sunken lesions appear on the fruit surface, and after expansion the whole fruit rots, with gray spore masses first produced at cracks in the fruit skin, then spreading to the whole fruit, and finally growing a gray mold layer. Sometimes black sclerotia or gray mycelial blocks can be produced on the diseased parts.
Control methods:
Grape gray mold: Lvdasheng at 600 times + Yingde at 1500 times + pyrimethanil at 1000 times.
5. Grape anthracnose:
At the early stage of disease, pinhead-sized brown spots appear on the fruit, gradually expanding into round spots, slightly sunken, with black small spots arranged in concentric rings on the surface, and pink sticky matter oozing out when humid. The lesions may extend to most or all of the fruit; the fruit soft-rots, easily falls off, and after shrinking becomes a mummified fruit. When fruit clusters, the rachis and leaf stalks are infected, the lesions are dark brown, sunken and oblong, and can cause the fruit clusters below them to dry up and fall off.
Control methods:
Grape anthracnose: when conidia appear from mid-to-late June to early July, spray once about every 10 days with 800~1000 times Aokai wettable powder + 10% benzi at 1000 times, or Lvdasheng at 500~800 times solution + Shike at 1000 times, both of which achieve good results. However, pesticides should be alternated to improve efficacy.
6. Grape black pox:
After leaves are infected, pinhead-sized brown small spots first appear, then develop into yellow-brown round lesions 1-4 mm in diameter, the center turns gray, and finally the diseased tissue dries, hardens, falls off and forms shot holes. Young leaves after infection are mostly twisted and shrunken into deformities. Fruit is not easily infected by this disease after coloring. When green fruit is infected, brown round spots first appear, the center of the round spots is gray-white and slightly sunken, and the margin is reddish-brown or purple, resembling a "bird's eye"; multiple small lesions combine into large spots; in the later stage the lesions harden or crack. Diseased fruit is small, sour and of no edible value. New shoots, leaf stalks, fruit stalks and tendrils: after infection, round brown small spots first appear, then turn gray-black, and the center sinks into dry-cracked canker spots; in severe cases they finally dry up or die.
Control methods:
Grape black pox: during the grape growing period, from the start of leaf unfolding until the fruit is 1/3 ripe, spray once every 15-20 days; the pesticide can be 80% Lvdasheng wettable powder at 600 times solution, or Kejia at 1000 times solution + benzi at 2500 times. When the disease occurs, use Xianlang at 1500 times solution + 80% Lvdasheng wettable powder at 600 times solution, or “Xinsheng” at 1500 times solution for treatment, alternating use 2-3 times.