Full analysis of the key technical points for the prevention and control of wolfberry pests and diseases

Wolfberry pest and disease prevention and control is one of the main contents of wolfberry orchard management. In the management of the wolfberry growing season, pest and disease prevention and control accounts for one third of the workload. Although the level of wolfberry yield and the quality of the product are closely related to variety and fertilizer, achieving the goals of safety, high quality, and high yield, producing green wolfberry products, and gaining an advantage in domestic and international markets depends on the level of pest and disease prevention and control. The main pest and disease prevention and control methods are as follows:

(1) Wolfberry anthracnose

Symptoms Wolfberry anthracnose, commonly known as black fruit disease, mainly damages green fruits, young branches, leaves, buds, flowers, and so on. When green fruits are infected, small black spots or irregular brown spots first appear on the fruit surface. During continuous rainy weather, the lesions continuously expand, and half the fruit or the entire fruit turns black. When dry, the fruit shrinks; when humidity is high, many orange-red gelatinous small dots grow on the diseased fruit; when young branches, leaf tips, and leaf margins are infected, brown semicircular lesions are produced, which turn black after expansion and become wet and rotted under high humidity, with sticky droplet-like orange-red small dots appearing on the surface of the diseased part, namely the pathogen's acervuli and conidia.

Pathogen Glomerella cingulata (Stonem.) Spauld. et Schrenk is called Glomerella cingulata, belonging to the phylum Ascomycota fungi. Its asexual state is Colletotrichum gloeosporioides (Penz.) Sacc., called Colletotrichum gloeosporioides, belonging to the class Deuteromycetes fungi. The acervuli are produced under the epidermis of diseased fruits. The mycelium accumulates in the intercellular spaces of the subepidermal tissue, forming dark brown acervuli, disc-shaped, with a raised center, 100-300 μm in size, with few setae. Later, the acervuli push open the fruit skin and cuticle, and conidiophores are produced on the disc, club-shaped, 12-21 × 4-5 (μm) in size; conidia are cylindrical, 11-18 × 4-6 (μm) in size. The suitable relative humidity for conidial germination is 100%, and they do not germinate when humidity is below 75%. They germinate in large numbers after 24 hours in water.

Transmission routes and disease conditions The fungus overwinters as mycelium and conidia on wolfberry trees and on diseased residual fruits on the ground. In the following spring, it mainly relies on rainwater to splash apart the conidia that are stuck together and spread them to young fruits, flowers, and buds, invading through wounds or directly. The incubation period is 4-6 days. The disease spreads quickly in rainy years and rainy seasons, showing a pattern of major peaks after heavy rain and minor peaks after light rain. A water film on the fruit surface favors spore germination. When there is no rain, spores germinate at night when there is a water film or dew drops on the fruit surface. In dry years or dry rainless seasons, the disease is mild and spreads slowly. It begins to occur from mid-May to early June and breaks out from mid-July to mid-August. When damage is severe, the diseased fruit rate can reach as high as 80%.

Prevention and control methods (1) After harvest, promptly prune diseased branches and diseased fruits, remove diseased residual fruits on the trees and on the ground, and bury them deeply or burn them in a centralized manner. Before the first rainfall in June, remove diseased residual fruits on the trees and on the ground again to reduce the initial infection source. (2) Before the first rainfall in June, spray once first, and add an appropriate amount of urea to the spray solution to kill overwintering pathogens and enhance tree disease resistance. (3) After disease onset, focus on spraying after rainfall. Spraying should be carried out within 24 hours after rain to prevent the spread and germination and invasion of conidia. (4) During the disease period, prohibit flood irrigation. After rain, drain accumulated water from the wolfberry orchard. Watering should be done in the morning to control field humidity and reduce dew formation on the fruit surface at night. (5) During the disease period, promptly control aphids and mites to prevent pests from carrying spores and causing wounds. (6) At the early stage of disease onset, begin spraying 25% carbendazim? wettable powder 500 times solution, 80% anthracnose thiram wettable powder 800 times solution, 25% shibaike emulsifiable concentrate 800 times solution, 50% shibagong or shibaike wettable powder 1000 times solution, 75% chlorothalonil wettable powder 1000 times solution plus 70% mancozeb wettable powder 1000 times solution, and 50% kemiedan (benomyl) wettable powder 800 times solution. Apply once every about 10 days, with continuous control 2-3 times. In addition, it has been reported that spraying red jute anthracnose fungus or citrus leaf anthracnose fungus at the early stage of disease onset has control efficacy similar to 80% anthracnose thiram wettable powder 800 times solution and is pollution-free, belonging to biological control methods. It can be tried in production.

(2) Wolfberry powdery mildew

Symptoms It mainly damages leaves. Nearly circular white powdery mildew spots form on both sides of the leaves, and later expand until the entire leaf is covered by white powder, forming white patches.

Pathogen Arthrocladiella mougeotii (Lév.) Vassilk. var. polysporae Z. Y. Zhao. is called Arthrocladiella mougeotii var. polysporae, belonging to the phylum Ascomycota fungi. Ascocarps are scattered or slightly clustered, brown to dark brown, 120-165 μm in diameter; appendages 28-81, rough at the base, light yellowish brown, short club-shaped or finger-shaped, some with septa, 0.6-1 times the length of the ascocarp, with 11-31 asci; asci oval to oblong, stalked, 59-74 × 14-21 (μm) in size, containing 2-4 ascospores; ascospores oval to oblong, 13.8-21.3 × 12-15 (μm) in size.

Transmission routes and disease conditions: In northern China, the pathogen overwinters as cleistothecia with diseased residues left on the soil surface, and in the following spring releases ascospores for initial infection. In southern China, the pathogen sometimes produces cleistothecia or overwinters as mycelium on the host. After disease occurrence in the field, conidia are produced on diseased parts and spread by airflow for secondary infection. When conditions are suitable, spores germinate and produce infection hyphae that directly invade through epidermal cells and produce haustoria in the epidermal cells to absorb nutrients, while the mycelium spreads continuously over the host surface by appressoria, and at the end of autumn forms cleistothecia or continues to overwinter as mycelium on living hosts.

Prevention and control methods (1) In late autumn and early winter, remove diseased residues and fallen leaves, and bury them deeply or burn them in a centralized manner. (2) Pay attention to ventilation and light transmission in the field. Do not plant too densely. When necessary, thin out excessively dense branches. (3) At the early stage of disease onset, spray 36% thiophanate-methyl suspension concentrate 500 times solution or 50% kemiedan (benomyl) wettable powder 800 times solution, 60% fangmeibao No. 2 water-soluble powder 1000 times solution, 20% triadimefon emulsifiable concentrate 1500 times solution, 30% basic copper sulfate (lüdebao) suspension concentrate 400 times solution, 45% crystalline lime sulfur 150 times solution, once every about 10 days, with continuous control 2-3 times. In areas where resistance to the above fungicides has developed, 40% fusilazole emulsifiable concentrate 7000-8000 times solution can be used instead, once every 20 days, for 1 or 2 treatments. Stop applying chemicals 3 days before harvest.

(3) Root rot

Symptoms: It damages the root and stem base. At the beginning of disease onset, the fibrous roots turn brown and rot, then spread to the main root, which turns black and rots. In severe cases, the outer bark rots and peels off, leaving only the xylem, and finally the entire plant dies. Wolfberry root rot mainly damages the plant roots and stem base. Diseased plants appear externally as yellowing and wilting leaves. When diseased plants are dug up and the roots and stems are dissected, the affected parts are seen to turn brown to dark brown, and in some cases the cortex rots and falls off, exposing the xylem. The vascular bundles inside the root and stem also turn brown. When moist, white to pink powdery fungal signs sometimes appear on the surface of the affected parts (pathogen conidiophores and conidia).