Detailed Explanation of Major Diseases of Woody Flowers and Their Control Methods

Tree and flower diseases and pests have always been a difficult problem that hinders the healthy growth of plants and troubles the vast number of landscaping workers. How to detect diseases and pests and how to control them concerns the overall situation of the landscaping industry. The main diseases of trees and flowers and their control methods are listed below for the reference of the vast number of landscaping workers.

Powdery mildew

Hosts: Chinese rose (Rosa chinensis), rose (Rosa multiflora), Rosa davurica, Impatiens balsamina, Aster, poplar, willow, Sophora japonica, oak, rose (Rosa rugosa), dahlia, chestnut, walnut, Paulownia, mulberry, hackberry, Ailanthus altissima, apple, pear, peach, lilac

Damage symptoms: It damages leaves, branches, and flower stalks; a layer of white powdery substance grows on flower buds, leaves curl, branches become deformed, and in severe cases flowers are few and small, or the plant even dies.

Control methods:

1. Before budding in early spring, thoroughly prune out diseased branches and leaves, burn them in a centralized manner, and then spray 3-4 degrees lime-sulfur mixture.

2. During the growing season, spray 50% ambam or 70% thiophanate-methyl at 800-1000 times dilution, or 25% carbendazim at 500-800 times dilution.

Black spot

Hosts: Chinese rose (Rosa chinensis), rose (Rosa multiflora), Rosa davurica, Rosa xanthina, Prunus triloba, poplar, walnut, tung tree

Damage symptoms: It mainly damages leaves. Purple-black-brown or brown round spots or irregular concentric ring spots grow on the leaves, causing leaf drop.

Control methods:

1. Promptly remove dead branches and fallen leaves and burn them in a centralized manner.

2. Depending on the severity of the disease, spray 100-160 times equal-amount Bordeaux mixture, or 70% thiophanate-methyl or 50% carbendazim at 500-800 times dilution.

Rust

Hosts: rose (Rosa multiflora), rose (Rosa rugosa), Chinese rose (Rosa chinensis), daylily, chrysanthemum, spruce, larch, masson pine, Yunnan pine, black pine, Chinese pine, Populus tomentosa, jujube.

Damage symptoms: It damages leaves, stems, flower stems, and flower buds, producing orange-yellow summer spore piles and black winter spore piles.

Control methods:

1. When diseased plants are found, remove them promptly.

2. Protect with chemicals during the growing season; spray 65% zineb at 500-600 times dilution or 97% sodium dimethyldithiocarbamate at 250-300 times dilution (with 0.1-0.2% laundry detergent added).

Gray mold

Hosts: tree peony, cyclamen, chrysanthemum, Chinese peony, grape, poplar, willow

Damage symptoms: It damages leaves, stems, and flowers. Purple-brown or brown lesions appear, and gray mold-like growth develops. Lesions on stems become soft and rotted, causing the plant to collapse.

Control methods:

1. Ensure good ventilation and light penetration, promptly prune out diseased branches and leaves, and burn them in a centralized manner.

2. Protect with chemicals; spray 120-160 times equal-amount Bordeaux mixture or zineb at 800-1000 times dilution.

Brown spot

Hosts: Prunus triloba, chrysanthemum, Chaenomeles speciosa, pyrethrum, poplar, Russian olive

Damage symptoms: Brown or dark brown round lesions appear on damaged leaves; the leaves gradually turn black and die.

Control methods:

1. In winter and spring, thoroughly remove diseased leaves and branches and burn them.

2. Protect with chemicals during the growing season; spray 160 times equal-amount Bordeaux mixture or zineb at 600 times dilution.

Pine seedling needle blight

Hosts: masson pine, black pine, slash pine, Caribbean pine

Damage symptoms: The lower needles of the seedlings are affected first, gradually spreading upward; yellow spots first appear on the needle surface, followed by small black mold spots.

Control methods:

1. Do not plant seedlings too densely.

2. Spray fungicides such as 500 times Tuzet or 700 times hexachlorobenzene.

Anthracnose

Hosts: orchid, cactus, hydrangea, magnolia, cyclamen, Chinese fir, oil tea, Paulownia, apple, crabapple, peach, pear, cherry, hawthorn, persimmon.

Damage symptoms: It damages leaves and stems; nearly round purple-brown or light brown lesions grow, with small black dots on them; in severe cases the leaves wither.

Control methods:

1. When diseased plants are found, prune them out promptly.

2. Ensure good ventilation and light penetration, and strictly control soil moisture.

3. In the early stage of disease, spray 50% carbendazim or 70% thiophanate-methyl at 500-600 times dilution.

Leaf mold

Hosts: tree peony, Chinese peony

Damage symptoms: It damages leaves and stems; the lesions are nearly round and purple-brown, showing obvious concentric rings; when humid, brown mold-like growth appears on the underside of the leaves; in severe cases, it causes a large amount of leaf scorch.

Control methods:

1. Promptly remove diseased leaves and branches to reduce the source of infection.

2. Pay attention to preventing waterlogging and cold damage.

3. Spray 160 times equal-amount Bordeaux mixture or 65% zineb at 500 times dilution.

Nematode disease

Hosts: cyclamen, chrysanthemum, rose (Rosa multiflora), dahlia, Impatiens balsamina, ginkgo.

Damage symptoms: One type damages leaves; the leaves are light green with light yellow to brown spots, and the leaves gradually wither; in severe cases the flowers are small or deformed, or the plant withers before flowering. The other type damages roots, forming galls, causing root rot; affected plants grow weakly, and leaves turn yellow or even die.

Control methods:

1. Soil disinfection: use 23-30 ml per sq m of DDT preparation or 5-8 mm per sq m of 80% dibromochloropropane on the seedbed.

2. When diseased plants are found, thoroughly pull them out and burn them, and carry out soil disinfection.

Viral disease

Hosts: dahlia, lily, tree peony, orchid, chrysanthemum, rose (Rosa multiflora), narcissus

Damage symptoms: Affected plants show symptoms such as mosaic, deformity, clustering, dwarfing, spotting, and stunting.

Control methods:

1. Strengthen quarantine work.

2. Promptly pull out diseased plants and burn them.

3. Promptly carry out control of disease-carrying insects (such as aphids, leafhoppers, whiteflies, etc.).

Damping-off

Hosts: pine, Chinese fir, larch, linden, Chinese toon, Schima superba, black locust, Chinese wingnut, elm.

Damage symptoms: The disease and pests occur on seedlings that have not yet become woody, with the greatest damage before and after emergence. Affected seedlings collapse in large numbers and die of drying out.

Control methods:

1. Disinfect seeds and soil.

2. Reduce the amount of irrigation during the seedling stage and avoid excessive moisture.

Root rot

Hosts: walnut, Chinese chestnut, Liriodendron chinense, pine, poplar.

Damage symptoms: After the seedlings become woody, the roots are infected by pathogens and turn black and moldy, the leaves turn brown, and in severe cases the whole plant dies.

Control methods:

1. Disinfect seeds and soil.

2. Reduce the amount of irrigation during the seedling stage and avoid excessively moist soil.

Rhizoctonia rot

Hosts: orchid, Dianthus, China aster, begonia, iris, Korean pine, larch, Mongolian pine, Chinese pine, Japanese red pine, Chinese fir.

Damage symptoms: It damages the stem base and roots of seedlings; the affected parts become brown or red-brown, constricted, and show damping-off or root rot.

Control methods:

1. Soil disinfection: formalin, 50 ml per sq m, diluted with 16-24 jin of water.

2. Promptly pull out diseased plants and spray amobam at 300-500 times dilution to prevent spread.

Stem rot

Hosts: ginkgo, Eucommia ulmoides, pine, cypress, Torreya grandis, dawn redwood, Japanese cedar, Pseudolarix amabilis, sweetgum, black locust, Chinese chestnut, mulberry, Chinese tallow, maple.

Damage symptoms: The root crown of affected seedlings turns brown; in the later stage the cortex shrinks, the inner cortex becomes spongy, and the seedlings dry out and die.

Control methods: Shade the seedlings in midsummer to prevent sunscald.

Southern blight

Hosts: oil tea, eucalyptus, Phoebe zhennan, Firmiana simplex, Catalpa, masson pine, citrus, apple

Damage symptoms: The stem base and root epidermis of affected seedlings rot, wilting symptoms appear on the leaves, and white mycelium is present; finally the whole plant dies.

Control methods:

1. Promptly remove diseased seedlings and burn them; disinfect the diseased soil with lime.

2. For lightly affected seedlings, pour 0.1-0.2% mercuric chloride solution thoroughly around the root crown; at ordinary times avoid water accumulation in the seedbed.

Root-knot nematode disease

Hosts: poplar, Sophora japonica, sample, willow, walnut, yellowhorn, Paulownia, hackberry, elm, maple, camphor, jujube

Damage symptoms: Soft round galls 0.5-2 cm in size appear on the roots of diseased seedlings; when cut open, white granular material, which is the nematode, is visible.

Control methods:

1. Disinfect the soil with methyl bromide.

2. Nursery land should be rotated; do not practice continuous cropping.

3. Promptly pull out diseased plants and burn them.

Poplar canker

Hosts: Populus tomentosa, Canadian poplar, white poplar, Simon poplar

Damage symptoms: Lesions appear on diseased plants or pathogens, concentrated on the middle and lower parts of the stem; the bark turns brown and slightly sunken, and in autumn bean-sized blisters form.

Control methods:

1. Remove diseased plants and burn them.

2. Excise the lesions and apply chemicals such as 0.1% mercuric chloride.

Bacterial soft rot

Hosts: iris, cyclamen, calla lily, hyacinth, wallflower

Damage symptoms: It damages reproductive organs such as rhizomes, corms, bulbs, and tuberous roots. Under dry conditions, the affected organs become powdery and shriveled; under high humidity, a soft outer shell encloses a foul-smelling slurry-like substance; in severe cases, the plant dies.

Control methods:

1. Storage disinfection: use formalin at 80 times dilution, and at the same time ensure ventilation.

2. Strictly select seedlings; materials cut from diseased parts must be disinfected with household streptomycin at 350-700 units per mm.

3. Promptly prune out diseased leaves, and disinfect tools with 75% alcohol or 0.1% potassium permanganate.