What are the key management points for rice at the heading and flowering stage?

       When rice encounters continuous low temperature and rainy weather at the heading stage, fungicides should generally be applied to control rice blast. For susceptible varieties, two applications should be made: at the breaking stage (10%-50% of rice in the field breaking) and at the full heading stage (80% of rice panicles in the field emerged). Suitable fungicides include isoprothiolane, tricyclazole, prochloraz, and others. Among them, isoprothiolane, tricyclazole, and similar fungicides have extremely strong systemic translocation properties; generally, if there is no rain for 2-3 hours after application, the control effect can be ensured. Judging from the weather forecast, thunderstorms are common in many areas recently, so spraying can be done in the gaps between rains as conditions permit. When there is water on rice leaves after rain, the amount of water used should be appropriately reduced, and fine spraying or mist sprayer application should be used. In this way, the high-concentration fungicide solution falling on water-covered rice leaves can be secondarily diluted and evenly distributed on the leaf surface, avoiding a large amount of fungicide solution dripping from the leaf surface and affecting the control effect.

       To control rice false smut, fungicides should generally be applied about 1 week before the breaking stage of rice. According to experimental research conducted many years ago by the Jiangsu Academy of Agricultural Sciences and other institutions, using validamycin to control rice false smut is most effective when applied about 1 week before the breaking stage of rice; applying it at the breaking stage has almost no control effect. From recent experimental demonstrations and large-scale production application, azole fungicides such as difenoconazole·propiconazole and tebuconazole, which are suitable for controlling rice false smut, copper preparations such as copper hydroxide sulfate and copper succinate-glutarate, and fungicides such as prochloraz also have a certain control effect on rice false smut when used at the heading stage of rice. For fields where no fungicide was applied about 1 week before the breaking stage of rice to control rice false smut, consideration can be given to selecting the above fungicides at the heading stage according to local conditions to control rice false smut.

       Excessive use of azole fungicides at the heading stage of rice, especially excessive application when rice growth is inhibited by low temperature and rainy weather, may affect rice heading and grain filling and fruiting. When applying fungicides, the dosage should be strictly controlled, and the dosage should not be blindly increased. Prochloraz and copper preparations such as copper hydroxide sulfate have good control effects on both rice false smut and rice blast, and normal use poses little risk of phytotoxicity to rice. These fungicides can be given priority at the heading stage of rice, or mixed or alternated with other fungicides.
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