Causes of Blight
Blight in rice seedlings often occurs due to insufficient disinfection of the nursery soil before planting. When the temperature inside the greenhouse is high and humidity levels are elevated, viable pathogens multiply rapidly, infecting the roots of young rice plants and causing disease. This condition is known as fungal blight. Additionally, under conditions of high temperature, high humidity, and poor light penetration, rice seedlings tend to develop elongated stems and leaves, weak root systems, and reduced water absorption capacity. If ventilation is improper or moisture levels become unbalanced, the seedlings may suffer from wilting, a condition referred to as physiological bacterial wilt. Rice seedlings are particularly vulnerable during the first 1.5 to 3-leaf stage, when their natural resistance is low, making them highly susceptible to both types of blight. Notably, early-stage disinfectants used in nurseries have little to no effect on bacterial wilt. Once the disease takes hold, it spreads rapidly across the seedbed, leading to significant losses in plant utility.
Identification of Seedling Blight
During the 1.5 to 3-leaf stage, symptoms of fungal blight may include yellowing and curling of the leaves, with the base of the leaves turning brown. Brown spots may appear on the leaf sheaths, and the roots may turn yellow-brown. A layer of fungal growth may be observed at the junction between the seed and the stem base, where the tissue becomes soft and prone to breaking. Clusters of affected seedlings may appear in the nursery, which is an early sign of infection. If not controlled promptly, the disease can quickly spread throughout the entire seedbed. In contrast, physiological bacterial wilt typically manifests before or around the 3-leaf stage, with the tips of the seedlings failing to exude water droplets. During dry weather, the seedlings may show blue discoloration and drying, with the heart and upper leaves appearing "hiccups" and eventually wilting. These symptoms are not contagious but should still be addressed immediately. Early preventive measures are essential. Spraying should be conducted during the 1.5 to 2.5-leaf stage, regardless of whether the disease has already developed, to ensure maximum protection and effectiveness.
New Technologies for Prevention
A new and effective method involves using a biological pesticide solution, diluted at a ratio of 1000 times, containing 30% active ingredient. This solution can be sprayed at a rate of 2 to 3 kg per square meter during the 1.5 to 3-leaf stage of the rice seedlings. The liquid not only moistens the soil but also enhances the immunity of the plants while eliminating fungi in the bed. This technique can be integrated with regular seedbed maintenance. The pesticide is a chitin-based biopesticide, non-toxic and safe for use in pollution-free rice, A-level green food rice, and AA-level organic rice. Under normal conditions, one application with a fine mist sprayer is sufficient, though a second spray after 10 days can improve results. The cost per square meter is relatively low—about the price of a dime—making it a cost-effective and reliable preventive measure. According to scientific studies, chitin-based biopesticides act as strong inducers that not only kill bacteria but also promote rapid root development, offering excellent protection against blight and bacterial wilt. Field tests have shown that this method significantly reduces the occurrence of diseases such as rice leaf spot, bacterial brown spot, rice blast, and black rot.
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