In recent years, rape virus disease has been reported across all rapeseed-producing regions in the country. This disease primarily affects Brassica napus, and one of its common symptoms is systemic spotting. The infection typically starts on older leaves, where symptoms become noticeable early on and gradually spread to younger foliage. At the initial stage, small, transparent lesions appear, which later develop into nearly circular spots measuring 2 to 4 mm in diameter. These spots have a dark brown center, with necrotic areas surrounding them. On the stems, black, fusiform, or elongated stripe-like lesions appear, spreading from the lower parts toward branches and fruit stalks. Stem lesions are often longitudinal or split, and flowers and pods may wilt or die prematurely. Infected pods show black necrotic spots and frequently become deformed.
The primary pathogen responsible for this disease is the Turnip mosaic virus (TuMV), which can significantly reduce rapeseed yields by 50% to 60%. The virus is mainly transmitted by aphids, particularly during the spring and autumn seasons when environmental conditions favor their proliferation. Dry or light rainy weather combined with high temperatures in autumn or spring creates favorable conditions for locust infestations and the migration of winged aphids, leading to widespread disease outbreaks. Early-sown or transplanted rapeseed in spring, as well as late spring-planted crops, are more susceptible to infection.
To manage the disease effectively, several preventive and control measures should be implemented. First, it's essential to select virus-resistant rapeseed varieties suitable for local conditions. Examples include Ningyou 7, Glycerol 5, Oyster Sauce 12, Oyster Sauce 13, Xiangza Oil No. 1, Rongyou No. 3, Yuyou No. 2, and Zhongshuang No. 4, all of which exhibit resistance to Turnip mosaic virus.
Adjusting sowing times based on seasonal rainfall forecasts is also crucial. If dry or less rainy conditions are expected in September and October, delaying sowing can help avoid peak aphid activity. Additionally, planting rapeseed fields away from cruciferous vegetable areas can reduce the risk of viral transmission.
For aphid control, insecticides such as dimethoate, 20% cyanogen, and horse cream should be applied promptly. In the early stages of the disease, spraying solutions like 0.5% antiviral mushroom proteoglycan hydrolysate diluted 300 times, 10% Virus King WP diluted 500 times, 1.5% plant disease emulsifier diluted 1000 times, or 83 Agent Increase Agent diluted 100 times can be effective. These treatments should be repeated every 10 days for 2 to 3 consecutive applications to ensure optimal control.
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