Identification methods and control techniques for diseases and pests of Schisandra chinensis

Diseases I. Leaf blight

1. Symptoms. Caused by infection with the leaf blight pathogen of Schisandra chinensis, it is a commonly occurring disease. It is prone to occur from late May to early August when temperatures are high, rain is frequent and ventilation is poor. The disease first starts from the leaf tip or leaf margin, with dark brown lesions appearing, gradually spreading downward and expanding to the entire leaf, and finally causing the whole leaf to turn dark brown, dry up and fall off. The fruit then shrinks, becoming early fruit drop.

2. Control. First, choose a plot with good ventilation. Second, strengthen field management, carry out pruning reasonably, and avoid excessive overlapping of branches and leaves and excessive canopy density. Create good ventilation and light conditions, reduce field humidity, and improve the microclimate among plants. Third, when central diseased plants are found, remove diseased leaves to reduce sources of infection. Fourth, after the disease occurs, spray with 50% thiophanate-methyl 1000-fold solution, 80% mancozeb 800-fold solution, or 80% amobam 1000-fold solution, spraying once every 7 days, for 2 to 3 sprays.

II. Root rot

1. Symptoms. Caused by infection with the root rot pathogen of Schisandra chinensis, it is a commonly occurring disease. It occurs during the rainy season from early July to mid-August, and is severe in waterlogged low-lying land, low-lying land, and plots with poor permeability. After the disease occurs, the leaves of the aboveground plant wilt and droop, and black spots appear at the junction between the roots and the ground surface, gradually spreading upward and downward, causing the roots to turn black and rot, the root bark to fall off, and the plant to die after a few days.

2. Control. First, choose plots with higher terrain, good drainage and relatively strong permeability for planting Schisandra chinensis. Avoid waterlogged low-lying land and low-lying land. Second, during the rainy season, accumulated water should be drained promptly to prevent waterlogging. Third, after the disease occurs, spray the root zone with 50% carbendazim 1000-fold solution or 50% hymexazol 1000-fold solution.

III. Powdery mildew

1. Symptoms. Caused by infection with the powdery mildew pathogen of Schisandra chinensis. It occurs in certain years. It is prone to occur in summer when it is dry and stuffy, at temperatures of 25 to 28°C. In the early stage of the disease, the leaf color fades or grayish-white patches appear, covered with a layer of white powder, the leaf surface is uneven, and the outline of the lesions is unclear. In severe cases, white powder covers the entire leaf, and the diseased leaves gradually curl, dry up and fall off.

2. Control. First, strengthen field management, tie the vines promptly, prune secondary shoots, distribute the branches and vines evenly on the trellis, and maintain ventilation and light. Second, plant at a reasonable density; planting must not be too dense, and nitrogen fertilizer must not be excessive. Apply nitrogen, phosphorus and potassium in combination to prevent excessive vegetative growth of leaves and vines. Third, in winter, cut off diseased branches, sweep up diseased leaves and diseased fruits, and burn them in a centralized manner. Fourth, after the disease occurs, spray with 25% dinocap 500-fold solution, 50% thiophanate-methyl 1000-fold solution, or 80% mancozeb 1000-fold solution. Spray once every 7 days, for 2 to 3 sprays.

IV. Downy mildew

1. Symptoms. Caused by infection with the downy mildew pathogen of Schisandra chinensis. It is prone to occur in July to August of certain years with high temperature and abundant rain. On the upper surface of the leaves, relatively large light red lesions appear, round or nearly round, and there are also small polygonal lesions, gradually turning yellow or reddish brown. On the underside of the leaves, white mold-like substances are produced, and the leaves gradually dry up.

2. Control. First, remove fallen leaves, cut off diseased branches, pick off diseased leaves and diseased fruits, and reduce sources of disease. Second, prune reasonably, improve ventilation and light conditions, drain accumulated water promptly, and increase the application of phosphorus and potassium fertilizers to enhance disease resistance. Third, before the disease occurs, spray equal-amount Bordeaux mixture to control the disease. After the disease occurs, spray with 50% thiophanate-methyl 1000-fold solution or metalaxyl-mancozeb 800-fold solution, spraying once every 7 days, for 3 to 4 consecutive sprays.

Herbicide injury

1. Symptoms. Schisandra chinensis is sensitive to any herbicide, and is especially most sensitive to acetochlor-atrazine mixture. When the herbicide acetochlor-atrazine mixture is applied on the windward side to close off weeds, the spray droplets drift with the wind to Schisandra chinensis fields within 200 m on the leeward side and can still cause herbicide injury. On the day of spraying, the leaves of the entire affected Schisandra chinensis plant show water-soaked patches, which spread over the whole leaf and gradually dry up. In mild cases, the growing point can continue to sprout and form new leaves; in severe cases, the growing point dies and cannot sprout.

2. Control. When choosing a plot for Schisandra chinensis, keep it far away from corn and soybean fields. Alternatively, do not apply pre-emergence herbicides in corn and soybean fields. The selected land should be contiguous, or close to grape fields, vegetable fields, medicinal herb fields and other crops where herbicides cannot be applied, so as to avoid herbicide injury and affect the growth of Schisandra chinensis. After herbicide injury appears, topdress fertilizer promptly to promote growth.

Pests

I. Black velvet chafer

1. Damage symptoms. Adults cause damage; Coleoptera, Scarabaeidae; it is an early-stage pest of Schisandra chinensis. Adults are 7 to 8 mm long and 4 to 5 mm wide, with a raised dark brown and glossy back, and each of the two elytra has 9 raised lines. In early May, when the daily average temperature remains above 10°C for 5 days, adults emerge from the soil in large numbers, and damage is severe in windless and warm weather. The damage period is from early May to late June. Schisandra chinensis sprouts and unfolds leaves from late April to early May, and is the earliest crop in farmland to sprout and unfold leaves. After adults emerge from the soil, they feed on the leaf buds of Schisandra chinensis, eating the leaf buds completely and leaving the woody stems; at the edges and corners of fields, they also feed on dandelion, dock, and sow thistle, as well as the young buds of elm, poplar and willow trees.

2. Control. First, manual capture. Within a few days after emerging from the soil, black velvet chafers only crawl and do not fly; when the number of insects is small, manual capture can be carried out. Second, chemical control. When the insect population density is high and manual capture is difficult, chemical control can be carried out. The method is to spray 20% Shate 1000-fold solution, 4.5% cypermethrin 1500-fold solution, or 80% dichlorvos 1000-fold solution during the peak period of adult emergence and damage from 2 to 4 p.m. Third, trap and kill adults. Before adults appear in the afternoon, soak sprouting branches of elm, poplar and willow with 40% dimethoate emulsifiable concentrate 50-fold solution, and insert them into areas where adults are concentrated and occur, inserting one branch per sq m to trap and kill adults.

II. Leaf roller (soybean pyralid moth)

1. Damage symptoms. Larvae cause damage; Lepidoptera, Tortricidae. It occurs in July to August. Early-instar larvae feed on tender leaves; after the 3rd instar, they spin silk to roll the leaves up and feed on the leaf mesophyll inside the rolled leaves, damaging the leaves, affecting fruit development, and even causing fruit drop.

2. Control. Before the larvae roll the leaves, spray with 4.5% cypermethrin 1500-fold solution or 80% dichlorvos emulsifiable concentrate 1000-fold solution to eliminate them before leaf rolling. After the leaves are rolled, spray with 50% phoxim emulsifiable concentrate 1500-fold solution.