Apple brown spot disease has emerged as a significant threat to apple orchards in the past four to five years. The disease is becoming more prevalent, and in some cases, entire orchards have suffered severe losses. The symptoms of this disease affect both the leaves and fruits of the apple trees. Initially, small yellowish-orange, glossy spots appear on the leaf surface. These spots gradually expand into nearly round lesions with diameters ranging from 4 to 8 mm. The lesions are densely covered with tiny black spots—these are the reproductive structures of the pathogen—and often exude a pale yellow mucus. The affected areas become sunken, and on the underside of the leaves, a rust-like, beard-like structure can be observed.
The occurrence of the disease is closely related to temperature conditions. The pathogen does not germinate when temperatures are below 14°C or above 30°C. The optimal temperature range for infection is between 17°C and 20°C. Therefore, the main infection period occurs from mid-April to May, and the disease typically infects only once per season. As temperatures rise later in the season, re-infection is unlikely.
For prevention and control, it's crucial to act early, as the disease becomes more difficult to manage once it's established. The primary period for treatment should be from mid-April to late May. The most commonly used fungicides for controlling this disease are azole-based products. However, many azole fungicides can be harmful to both the environment and human health if not used properly. To ensure safety, it is recommended that farmers prioritize using high-quality, reputable products. For example, Bayer’s Tebuconazole and Yantai Green Cloud’s Cymoxan have been widely used for years and are considered safe and effective. If you're unsure about the application method or the brand's reliability, it's best to proceed with caution and consult local agricultural experts before use. Proper management and timely intervention are key to minimizing the impact of this disease on apple production.
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