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Bordeaux Liquid Can Effectively Control the Occurrence of Apple Brown Spot in Rainy Season
In the rainy season, managing brown spot disease in apple orchards becomes a critical challenge for farmers. According to the Funan County Bureau of Agriculture, Bordeaux mixture has proven to be an effective solution for controlling this disease during wet weather. This method is especially important given the high humidity and prolonged rainfall that create ideal conditions for the pathogen to thrive.
Apple brown spot is a typical rain-related disease, and continuous precipitation plays a key role in its spread. The pathogen responsible for the disease, *Alternaria alternata*, produces conidia (spores) rapidly under high humidity. After the first rain, spores can reappear within 24 hours, leading to repeated infections. Even after several days of rain, the pathogen continues to produce spores, making it difficult for most fungicides to maintain long-term protection.
Systemic fungicides like tebuconazole and flusilazole are effective against the pathogen but only within 5 to 7 days after infection. Once symptoms appear, these treatments struggle to control the spread. Therefore, timely application based on accurate forecasting is essential. Protective fungicides such as mancozeb and copper-based products offer good initial protection, but their effectiveness diminishes quickly under heavy rain. By the second or third day of continuous rain, the protective layer on leaves is often washed away, leaving them vulnerable to new infections.
Bordeaux mixture stands out due to its strong resistance to rain, offering sustained protection over multiple rainy days. In regions like Yantai, where apple production is common, farmers typically apply Bordeaux mixture before the start of the rainy season. The recommended ratio is usually 1 part copper sulfate, 2–3 parts quicklime, and 200–240 parts water. The amount of lime may be increased if the rain is heavy or prolonged, ensuring better adhesion of the mixture to the leaves.
During intervals between applications, systemic fungicides can be used to manage any existing infections. However, it's important to avoid applying Bordeaux mixture during the apple bagging period in April or May to prevent potential phytotoxicity. Proper timing and application techniques are crucial for maximizing effectiveness while minimizing risks.
To effectively manage brown spot during the rainy season, early intervention and consistent use of appropriate fungicides are necessary. Spraying protective agents like Bordeaux mixture before the rainy season begins can help prevent the onset of the disease. Combining this with targeted systemic treatments ensures comprehensive control and reduces the risk of widespread infection. Proactive management and careful planning are key to protecting apple crops from this challenging disease.