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Large-scale leaf-rolling of the central leaves of rice may be related to excessive application of quinclorac

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For some time recently, hundreds of readers across our province have called to report large-scale leaf-rolling of the central leaves of rice seedlings, which is even more common in direct-seeded rice production. Many readers brought in diseased plants. The root systems of the diseased plants are generally fairly normal, and there are no obvious disease spots or other symptoms on the leaves. After examining the submitted diseased plants, relevant experts from the Institute of Plant Protection of the Provincial Academy of Agricultural Sciences and other units preliminarily diagnosed that the leaf-rolling of the central leaves of rice is not caused by viruses or other pathogenic microorganisms, but may be phytotoxicity caused by herbicides such as 2,4-D and quinclorac, or may be caused by physiological

For some time recently, hundreds of readers across our province have called to report large-scale leaf-rolling of the central leaves of rice seedlings, which is even more common in direct-seeded rice production. Many readers brought in diseased plants. The root systems of the diseased plants are generally fairly normal, and there are no obvious disease spots or other symptoms on the leaves. After examining the submitted diseased plants, relevant experts from the Institute of Plant Protection of the Provincial Academy of Agricultural Sciences and other units preliminarily diagnosed that the leaf-rolling of the central leaves of rice is not caused by viruses or other pathogenic microorganisms, but may be phytotoxicity caused by herbicides such as 2,4-D and quinclorac, or may be caused by physiological reasons.

In recent years, it has been widely found in production that the control effect of quinclorac against older barnyardgrass at the 4-leaf stage and above is poor, and the dosage must be increased to achieve a better control effect. In production, when using such agents, the dosage is generally increased, and the per-mu dosage of 50% quinclorac wettable powder is generally around 50 grams. Especially in direct-seeded rice fields, from the 2-leaf 1-heart to 3-leaf stage of rice, the older barnyardgrass in the field is usually at the 4-leaf stage or above, and the dosage of quinclorac must be increased to control it effectively. However, using quinclorac at a high dosage during the rice seedling stage carries a great risk of phytotoxicity.

In addition, this year many places in our province had flooded rice, and direct-seeded rice was flooded more severely. Flooded rice seedlings are weaker in quality and have poor root growth, so phytotoxicity is more likely to occur when quinclorac is used at a high dosage.

In response to the large number of cases of leaf-rolling of the central leaves of rice currently appearing in production, if the rice field was previously treated with an excessive amount of herbicides such as quinclorac before the disease occurred, gibberellin, brassinolide and the like can be used to alleviate the phytotoxicity. Gibberellin can stimulate rice to grow taller, but it has an inhibitory effect on tillering. When used at the tillering stage, it should be diluted 50000 times; after the late tillering stage, the concentration can be slightly higher, and dilution 30000 times is sufficient. For severely damaged seedlings, it is best to pull them out and transplant from dense areas to sparse areas in the field. Strengthen fertilizer and water management in the affected fields, and after some time the affected rice plants can generally gradually resume growth.

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