Apple brown spot disease is one of the most common diseases encountered in fruit tree cultivation, often occurring in seasons with high temperatures and heavy rainfall. Factors such as poor management, delayed spraying after bagging, inadequate drainage, and poor ventilation can lead to the occurrence of brown spot disease. So, how can we effectively prevent and treat apple brown spot disease? Let's find out together.
1. Symptoms
The disease primarily affects the leaves of the apple tree, with lesions appearing brown and irregularly bordered with green, hence the name green-edge brown spot. There are three types of lesions:
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Concentric ring pattern: Circular lesions with yellow perimeters, dark brown centers, and black dot-like structures arranged in concentric rings. Surrounding the lesions is a green halo.
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Spine-like: Lesions extend outward like spines, without a defined border, and are numerous but small.
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Mixed type: Large lesions, nearly circular or irregular, dark brown with gray-white centers, accompanied by small black dots but lacking distinct concentric rings.
2. Disease Development
The pathogen of brown spot disease mainly overwinters on fallen leaves. The severity of the disease in the winter depends on the quantity of infected leaves in one's orchard by the end of October. The infection period of brown spot disease is divided into four stages: initial infection (May-June), accumulation period (July), peak period (August-September), and pre-overwintering period (October-November).
3. Prevention and Treatment
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Prudent Pruning: Poor ventilation and insufficient sunlight in the orchard, or excessive fruit setting, can decrease the vigor of apple trees, making them more susceptible to brown spot disease. Therefore, timely and prudent pruning according to the growth status of the trees, along with appropriate thinning of flowers and fruits, can improve tree vigor and disease resistance.
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Spray Protection: Brown spot disease is prevalent in the hot and humid months of May and June. Therefore, spraying should commence in mid-May for apple tree protection, with applications every 15 days for 3-4 consecutive times to shield the trees from fungal infection.
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Drainage Attention: Excessive soil moisture can hinder root respiration and nutrient absorption, leading to reduced tree vigor. Moreover, excess soil moisture can create a humid environment in the orchard, accelerating the spread of fungal pathogens. Therefore, timely drainage during the rainy season can enhance tree vigor and reduce fungal spread.
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Pathogen Removal: Brown spot disease overwinters on fallen leaves, senescent bark, diseased fruits, diseased branches, dead branches, and weeds. Therefore, during autumn cleanup, promptly remove fallen leaves, senescent bark, diseased branches, dead branches, and weeds from the orchard, and dispose of them properly to reduce overwintering pathogens.
Above are the effective methods for preventing and treating apple brown spot disease. The rapid spread of brown spot disease can severely damage apple leaves and affect the quality and yield of apples if not promptly controlled.
