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A Detailed Guide to Controlling Common Pests and Diseases of Osmanthus

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1. Leaf spot disease: It mainly damages the leaves. Brown small spots appear first, and the lesions are round or irregular. Later, the center is gray to grayish white, and the edges are reddish brown. Blackish gray mold-like growth appears on the lesions. High temperature and high humidity are often the triggering factors. It spreads through wind and rain and causes infection. After October, the disease gradually subsides
1. Leaf spot disease: It mainly damages the leaves. Brown small spots appear first, and the lesions are round or irregular. Later, the center is gray to grayish white, and the edges are reddish brown. Blackish gray mold-like growth appears on the lesions. High temperature and high humidity are often the triggering factors. It spreads through wind and rain and causes infection. After October, the disease gradually subsides.Control: 1) In winter, prune to remove diseased leaves and clear away fallen diseased leaves, and burn them in a centralized manner; 2) In early May, spray 1:2:100-200 Bordeaux mixture, and afterward spray 50% benomyl at 1000 to 1500 times dilution, or pyrazophos at 500 times dilution, or 70% thiophanate-methyl at 1000 times dilution.

2. Blight spot disease: When leaves are damaged, it mostly starts from the leaf tip and leaf margin. The small spots are light brown, then expand into round or irregular shapes. The lesions may connect with one another and reach 1/3 to 1/2 of the leaf, are grayish brown, and have green edges. In the later stage, small black dots appear on the lesions. When temperature and humidity are high, ventilation is poor, and plants grow weakly, the disease is more severe. It generally occurs from July to November and spreads through wind and rain.Control: 1) In the early stage of the disease, spray 65% zineb at 500 times dilution or 1:2:200 Bordeaux mixture; 2) Afterward, spray 50% carbendazim wettable powder at 800 to 1000 times dilution or 50% benomyl wettable powder at 1000 to 1500 times dilution.3. Slug moth: Green or yellow-green, with a white dorsal line. It is most likely to occur on the underside of leaves, feeding on the leaf mesophyll and leaving the epidermis.Control: Before the larvae descend from the tree to spin cocoons, loosen the soil around the trunk to attract the larvae to gather and spin cocoons, then collect and destroy them. Alternatively, spray Bt emulsion containing more than 10 billion spores/ml at 500 to 800 times dilution. In addition, 2.5% deltamethrin emulsifiable concentrate or 20% fenvalerate emulsifiable concentrate at 3000 times dilution can also be sprayed.4. Scale insects: In the Yangtze River basin, 2 to 3 generations can occur. The most serious damage is from May to June and from August to September. They like to gather on the shaded side of main shoots and at branch forks, or on twigs and leaves. Both adults and nymphs secrete honeydew, causing sooty mold in ornamental plants.Control: High temperature and high humidity favor their occurrence. When only a small number occur, they can be gently brushed off with a soft brush, with good results. In summer, spraying 0.3 to 0.5 degrees Baume lime sulfur mixture is most beneficial, or 50% monocrotophos emulsifiable concentrate at 1500 times dilution, used alone or in mixture, spraying once every 7 to 10 days, for 2 to 3 consecutive sprays.5. Red spider mite: It often occurs under high temperature and drought conditions.Control method: During dry weather, attention should be paid to irrigation and combined fertilization to promote vigorous plant growth and enhance insect resistance. When using chemical pesticides, attention should be paid to frequent rotation, because after the application of certain highly toxic pesticides, resistance may develop. Spraying 40% fenpropathrin emulsifiable concentrate at 2000 to 3000 times dilution or 40% dimethoate emulsifiable concentrate at 1500 times dilution gives good control results

Control of Common Pests and Diseases of Osmanthus

1. Leaf spot disease: It mainly damages the leaves. Brown small spots appear first, and the lesions are round or irregular. Later, the center is gray to grayish white, and the edges are reddish brown. Blackish gray mold-like growth appears on the lesions. High temperature and high humidity are often the triggering factors. It spreads through wind and rain and causes infection. After October, the disease gradually subsides. Control: 1) In winter, prune to remove diseased leaves and clear away fallen diseased leaves, and burn them in a centralized manner; 2) In early May, spray 1:2:100-200 Bordeaux mixture, and afterward spray 50% benomyl at 1000 to 1500 times dilution, or pyrazophos at 500 times dilution, or 70% thiophanate-methyl at 1000 times dilution. 
 
2. Blight spot disease: When leaves are damaged, it mostly starts from the leaf tip and leaf margin. The small spots are light brown, then expand into round or irregular shapes. The lesions may connect with one another and reach 1/3 to 1/2 of the leaf, are grayish brown, and have green edges. In the later stage, small black dots appear on the lesions. When temperature and humidity are high, ventilation is poor, and plants grow weakly, the disease is more severe. It generally occurs from July to November and spreads through wind and rain. Control: 1) In the early stage of the disease, spray 65% zineb at 500 times dilution or 1:2:200 Bordeaux mixture; 2) Afterward, spray 50% carbendazim wettable powder at 800 to 1000 times dilution or 50% benomyl wettable powder at 1000 to 1500 times dilution. 
 
3. Slug moth: Green or yellow-green, with a white dorsal line. It is most likely to occur on the underside of leaves, feeding on the leaf mesophyll and leaving the epidermis. Before the larvae descend from the tree to spin cocoons, loosen the soil around the trunk to attract the larvae to gather and spin cocoons, then collect and destroy them. Alternatively, spray Bt emulsion containing more than 10 billion spores/ml at 500 to 800 times dilution. In addition, 2.5% deltamethrin emulsifiable concentrate or 20% fenvalerate emulsifiable concentrate at 3000 times dilution can also be sprayed. 
 
4. Scale insects: In the Yangtze River basin, 2 to 3 generations can occur. The most serious damage is from May to June and from August to September. They like to gather on the shaded side of main shoots and at branch forks, or on twigs and leaves. Both adults and nymphs secrete honeydew, causing sooty mold in ornamental plants. High temperature and high humidity favor their occurrence. When only a small number occur, they can be gently brushed off with a soft brush, with good results. In summer, spraying 0.3 to 0.5 degrees Baume lime sulfur mixture is most beneficial, spraying once every 7 to 10 days, for 2 to 3 consecutive sprays. 
 
5. Red spider mite: It often occurs under high temperature and drought conditions. Control method: During dry weather, attention should be paid to irrigation and combined fertilization to promote vigorous plant growth and enhance insect resistance. When using chemical pesticides, attention should be paid to frequent rotation, because after the application of certain highly toxic pesticides, resistance may develop. Spraying 40% fenpropathrin emulsifiable concentrate at 2000 to 3000 times dilution or 40% dimethoate emulsifiable concentrate at 1500 times dilution gives good control results.

Editor in charge: Molika

Control of Pests and Diseases of Osmanthus

          Osmanthus brown spot disease
In the early stage of the disease, small chlorotic yellow spots appear on the leaves and gradually expand into nearly round lesions, 2 to 10 mm in diameter, or become irregular lesions because the expansion of the lesions is restricted by leaf veins. The lesions are yellowish brown to grayish brown, with a yellow halo around the outside. Brown spot disease generally occurs from April to October, and old leaves are more susceptible than young leaves. The pathogen overwinters as mycelium on fallen diseased leaves, and in the following spring produces conidia for primary infection. The conidia are spread by airflow and raindrops.
Osmanthus blight spot disease
The pathogen of this disease mostly invades from the leaf margin and leaf tip, and occurs at the leaf margin and leaf tip. In the early stage of the disease, light brown small spots appear on the leaves and gradually expand into round or irregular lesions, later enlarging into nearly round or irregular grayish brown large lesions with dark brown edges. Blight spot disease occurs from July to November, and in greenhouses with poor environmental conditions it can occur throughout the year. The pathogen spreads and infects by conidia through wind and water. High temperature, high humidity, and poor ventilation favor the disease. When plants grow weakly, and on old leaves after overwintering and leaves in the lower part of the plant, the disease is more severe.
Osmanthus anthracnose
This disease infects osmanthus leaves. In the early stage of the disease, small chlorotic spots appear on the leaves and after gradual expansion form round, semicircular, or elliptical lesions. The lesions are light brown to grayish white, with a reddish brown ring around the edge. Under humid conditions, pale pink viscous acervuli appear on the lesions. Anthracnose occurs from April to June. The pathogen overwinters as acervuli in fallen diseased leaves and is spread by wind and rain.
Control measures
First, reduce the sources of infection. In autumn, thoroughly remove fallen diseased leaves. For potted osmanthus, promptly remove diseased leaves.  Second, strengthen cultivation management. Choose fertile soil or substrate with good drainage for planting osmanthus; increase the application of organic fertilizer and potassium fertilizer; planting density should be appropriate so as to allow ventilation and light penetration, reduce leaf surface humidity, and lessen the occurrence of the disease.
Chemical control. In the early stage of the disease, spray 1:2:200 Bordeaux mixture, and afterward spray 50% carbendazim wettable powder at 1000 times dilution or 50% benomyl wettable powder at 1000 to 1500 times dilution. In severely affected areas, when seedlings leave the nursery, they should be soaked and disinfected with 1000 times potassium permanganate solution.
Pest control
The main pest in home cultivation of osmanthus is mites, commonly known as red spider mites. Once infestation is found, it should be treated immediately. Mite clear, aphid-mite killer, or azocyclotin can be used for foliar spraying. The front and back of the leaves must be sprayed evenly. Once a week, for 2-3 consecutive times, and it can be cured.

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