Harmful symptoms of plant brown spot disease, control methods, and how it differs from anthracnose

Brown spot disease is a fungal disease caused by Rhizoctonia solani. It is widely distributed around the world and can infect all turfgrasses, with cool-season turfgrasses suffering the most severe damage, causing turf plants to die, leaving large bald patches in the lawn, and greatly damaging the lawn landscape. Now let us take a look at what chemicals to use to control brown spot disease!

Turf brown spot disease

[Symptoms] When the disease begins on turf, nearly circular patches of dead grass of varying sizes often appear. When conditions are suitable, the disease develops very quickly, and the diameter of the dead grass patches can expand from a few centimeters to one or two meters. Because the diseased plants in the center of the patch can recover, the dead grass patches often appear in a "frog-eye" shape, that is, green in the center with a withered-yellow ring at the edge.

[Control] Before or during periods of high temperature and high humidity, apply little or no nitrogen fertilizer, maintain a certain amount of phosphorus and potassium fertilizer, avoid continuous flooding irrigation and flood irrigation, and especially avoid watering in the evening. When dead patches appear on the lawn, guttation (or dew) should be removed as early as possible in the morning, which helps reduce the severity of the disease. In summer, do not cut the grass too short (generally 5-6 cm). For overly dense lawns, appropriately aerate and dethatch. Dead grass and clippings after mowing should be removed promptly. Disease-resistant (tolerant) varieties should be planted, and timely and effective chemical control should be carried out.

Poinsettia brown spot disease

[Symptoms] It damages leaves. At first, small yellow-brown spots appear, sometimes with dozens of diseased spots on one leaf. The small spots gradually expand into lesions 1-2 cm in diameter, with a light brown interior and a slightly angular margin showing concentric rings of varying shade. When the disease is severe, the lesions can reach 2-3 cm in diameter. In the dark gray area where diseased and healthy tissue meet, gray-white cottony mold develops.

[Control] Thoroughly remove diseased plant residues to reduce the primary infection source. Manage temperature and humidity well in the greenhouse, pay attention to ventilation and dehumidification, and improve air circulation.

Tulip brown spot disease

[Symptoms] Infected leaf buds develop poorly and become deformed and curled. Leaves that grow from damaged young buds become curled. If the environment is humid, a large amount of gray mold-like conidia is produced on diseased tissue, affecting neighboring healthy plants and causing leaf infection, so bulb growth is greatly affected. After flowers are damaged, white or light yellow-brown lesions first appear, then rapidly expand and wither and drop, or turn brown and dry up. Ring-like bands also appear on flower stalks, sometimes with conidial layers on them.

[Control] Remove diseased bulbs before planting and practice crop rotation. Once buds or flower buds showing symptoms of this disease are found, remove them immediately to control disease development. Before planting, soak bulbs in 2% formalin solution for 30 minutes, then dry and plant to reduce residual pathogens. During the growing period, spray 50% iprodione 1000x solution, or 50% procymidone 2000x solution, or 50% dimethirimol 1000x solution.

Osmanthus brown spot disease

[Symptoms] It occurs from April to October, with severe outbreaks in rainy seasons and years, and the disease spreads fastest from July to August. Old leaves are more severely affected than tender leaves, and weak-growing plants and plants transplanted in the same year are prone to the disease. Different osmanthus varieties differ in their resistance to brown spot disease; DanGui varieties have stronger resistance than JinGui and YinGui varieties.

[Control] When nursery stock leaves the nursery, remove diseased leaves and spray 1000x potassium permanganate solution for disinfection. Select disease-free plants as mother plants for propagation. Strengthen cultivation management, combine crown shaping, prune weak and diseased branches, adjust branch and leaf density, and enhance tree vigor. In the growing season, at the early stage of disease, spray the whole tree for protection, such as 70% copper hydroxide 300-500x solution, azoxystrobin 1000-1500x solution, or 50% carbendazim 500-600x solution.

Impatiens brown spot disease

[Symptoms] Impatiens brown spot disease, also called impatiens leaf spot disease, occurs in both northern and southern parts of China. The disease mainly occurs on leaves. Leaf lesions first appear as small light yellow-brown spots, then expand into circular or elliptical shapes, after which the center becomes light brown and the edge brown, with indistinct concentric rings. On severely infected leaves, lesions merge into patches, causing the leaves to turn brown and withered yellow, until the plant dies.

[Control] Impatiens prefers fertile sandy loam and is not tolerant of waterlogging. Therefore, sandy loam is suitable for planting to facilitate drainage. For potted impatiens, repot promptly after rain. In late autumn, diseased leaves and diseased plants should be collected and destroyed to reduce the source of infection for the next year. At the early stage of disease, use 25% carbendazim wettable powder 300-600x solution, or 50% thiophanate-methyl 1000x solution, or 75% chlorothalonil 1000x solution for control.

Morning glory brown spot disease

[Symptoms] Leaf lesions are scattered between veins and along leaf margins, nearly circular to polygonal, 2-6 mm in diameter, brown, or with a dark gray center and dark brown edge. The lesion surface produces a light black mold layer. When severe, lesions cover the entire leaf, and the leaf withers early.

[Control] Plant at appropriate density, avoid excessive watering, and spray 7500x plant growth supplement solution to promote early and rapid plant growth. Spray 75% chlorothalonil wettable powder 1000x solution plus 70% thiophanate-methyl wettable powder 1000x solution, or 40% carbendazim suspension concentrate 600x solution, or 50% procymidone wettable powder 2000x solution, once every 7-10 days, for 2-3 consecutive applications.

China aster brown spot disease

[Symptoms] China aster brown spot disease is a common leaf disease of China aster. When severe, the leaves wither and yellow, causing the whole plant to wilt. At first, nearly circular purple-brown lesions of varying sizes appear on the leaves, then turn black or black-brown. Later, the center of the lesion turns light gray, and fine small black dots reappear. When there are many lesions on a leaf, the whole leaf turns yellow and dries up. It generally starts from the lower leaves and gradually dies upward.

[Control] Choose well-drained sites for planting. Planting density should be appropriate. Choose disease-resistant varieties. Remove diseased leaves immediately when found. In late autumn, collect diseased fallen leaves and diseased residues and destroy them centrally. Spray 50% carbendazim wettable powder 1000x solution, or 80% zineb wettable powder 500-700x solution, or 1% Bordeaux mixture, or 75% chlorothalonil 500x solution for control. Spray once every 7-10 days.

Symptoms and control methods of cherry brown spot shot hole disease in landscape plants

[Pathogen] The pathogen of cherry brown spot shot hole disease overwinters in diseased leaves or shoot tips. The next year it produces spores that spread by wind and rain and invade through stomata. It begins each year in June and is severe from August to September. It is severe in years with much wind and rain, and plants are susceptible in summer drought and when tree vigor is weak. Bacterial shot hole disease overwinters in branch cankers and diseased buds. The next year, when temperatures rise, the bacteria spread by wind, rain, and insects and invade through stomata or lenticels. It begins in late April each year and is severe from June to July.

[Symptoms] It damages cherry leaves, causing them to dry up and fall off, forming shot holes. Besides cherry, the disease also infects stone fruit ornamental plants such as cherry, plum, peach, plum, and apricot. Shot hole disease can be divided into shot hole caused by fungi and by bacteria. Fungal shot hole, such as cherry brown spot shot hole disease, mainly damages leaves and also infects new shoots, mostly starting from the lower crown and gradually extending upward. At the early stage, needle-tip-sized purple-brown spots are scattered on the upper leaf surface, then expand into circular or nearly circular lesions 3-5 mm in diameter. The edge of the brown spot is purple-brown, and later gray-brown mold spots appear on the lesion. A separation layer forms at the lesion margin, and the lesion dries and falls off, forming a shot hole. In bacterial shot hole disease, however, lesions begin as water-soaked circular spots with a light yellow halo around them, with no mold spots on the diseased area; when moist, a dirty yellow secretion exudes from the lesion, and when dry, the lesion falls off to form a shot hole.

[Control methods]

1. In autumn, collect infected branches and leaves and burn them to reduce the source of infection.

2. Strengthen management measures, apply more organic fertilizer and phosphorus and potassium fertilizer, and promptly prevent drought and waterlogging to enhance tree vigor and improve resistance.

3. Before and after leaf expansion (especially for seedlings), spray 65% zineb 500x solution or 3-5 degrees Baume lime sulfur mixture or 1:1:100-200 3-5 degrees Baume lime sulfur mixture, etc.

4. For bacterial shot hole disease, spray zinc sulfate lime solution after leaf expansion (zinc sulfate 500 g, slaked lime 2000 g, water 120 kg).

Symptoms and control of oleander brown spot disease

Oleander is a woody plant in the Apocynaceae family. Its leaves and flowers are used as medicine, and it is toxic. It has the effects of strengthening the heart, promoting diuresis, resolving phlegm, and killing insects. It is distributed in most provinces and regions across the country. Brown spot disease is an important disease on oleander, commonly occurring in various places and causing serious damage.

Symptoms Brown spot disease mainly damages leaves. At first, purple-red small spots appear at the leaf tip or leaf margin, and after expansion they form circular, semicircular, to irregular brown lesions. The lesions have concentric rings. Later the center fades to white, and the red-brown edge is relatively wide. When humidity is high, a gray-brown mold layer can grow on both sides of the lesion, namely the pathogen's conidiophores and conidia.

Pathogen Cercospora neriella Sacc., called European oleander cercospora, belongs to the Deuteromycotina fungi. The stroma is dark brown, 25-125 μm in size. Conidiophores are light in color, uneven in thickness, gathered in bundles, with 0-3 septa, unbranched, with small spore scars at the apex, 5-35 x 3-5 (μm) in size. Conidia are cylindrical, with 1-5 septa, 15-50 x 3-5 (μm) in size. In addition, C. nerii-indici Yaman, called oleander cercospora, is also a pathogen of this disease.

Occurrence characteristics The brown spot pathogen overwinters as mycelium on diseased leaves or remains on the soil surface with fallen leaves. The next spring it produces conidia, which spread to oleander through wind and rain. Germinating spores invade through stomata or wounds and cause disease. It occurs from March to July, and is more severe when nursery stock grows too densely or is weak and slender.

Control methods

(1) Agricultural control

Plant at reasonable density, and do not plant too densely; manage fertilizer and water scientifically to cultivate strong seedlings; remove diseased leaves and burn them centrally to reduce the source of inoculum.

(2) Chemical control

At the early stage of disease, spray 50% benomyl wettable powder 1000x solution, or 25% carbendazim wettable powder 600x solution, or 36% thiophanate-methyl suspension concentrate 500x solution.

Differences between plant brown spot disease and anthracnose

Withering leaf disease is caused by external infection, with plants turning yellow, changing from green to yellow. Anthracnose spreads from the inside outward and looks as if it has rotted. It is an acute infectious disease of herbivorous animals caused by Bacillus anthracis. Brown spot disease is mainly a fungal disease caused by Rhizoctonia solani. New high-fat film and Husu Jiangjun can be used for control.