Qiuzan is registered for only two targets: rice sheath blight and rice false smut, both at a dosage of 45-50 mL/mu by spray application.
Two diseases, one dose—it looks simple. But the two diseases differ greatly in where they occur and in their control windows, and only by understanding this can you know how the fungicide should be applied.
I. Technical Positioning of Epoxiconazole
The product performance section states:
This product is a systemic triazole broad-spectrum fungicide that can be absorbed by plant stems and leaves and translocated upward and outward. Its active ingredient, epoxiconazole, inhibits the biosynthesis of ergosterol in pathogenic fungi, thereby blocking cell wall formation... It can also enhance chitinase activity in crops, causing the contraction of fungal haustoria and inhibiting pathogen invasion.
A few key points:
The mode of transmission is "upward and outward".This point is very important—it means that the agent is primarily transported with the transpiration stream to newly developing tissues.New leaves that emerge after application can also be protected.This is something that protective agents cannot achieve.
Dual mode of actionIt both inhibits ergosterol synthesis (disrupting the cell membrane) and enhances chitinase activity (preventing the pathogen from establishing haustoria). The combination of these two mechanisms results in stronger antimicrobial activity and also slows the development of resistance.
Common precautions for triazole fungicides.Triazoles have an inhibitory effect on crop growth at high doses (a side effect inherent to their mechanism of action), soThe dosage should not be increased arbitrarily.请提供需要翻译的中文段落内容。
2. Sheath blight: starts from the base
Rice sheath blight is caused by Rhizoctonia solani. The pathogen overwinters in the soil as sclerotia, which float on the water surface and, after transplanting, attach to the leaf sheaths at the base of rice plants, penetrating from the inner side of the sheaths.
Typical symptoms areCloud-patterned lesions, starting from the basal leaf sheath and extending upward from bottom to top.
Key control points:
Spray downward.Sheath blight develops on the middle and lower portions of the plant; spraying only the upper canopy with the nozzle is tantamount to no treatment at all. During application, the nozzle should be directed toward the base of the plant, or a sufficient spray volume should be used to allow the pesticide solution to run down along the stems.
Before or at the early stage of disease onset.The label states "control should be applied before the onset of rice sheath blight or at the early stage of the disease, with 1–2 applications." Once sheath blight spreads to the upper functional leaves, yield loss has already occurred.
The value of the systemic property of epoxiconazole in this context.The ability of the fungicide to translocate to newly emerging tissues means that leaf sheaths newly produced after application can also be protected, thereby reducing the number of repeated applications.
III. Rice false smut: the window is before the boot opening.
Rice false smut is caused by Ustilaginoidea virens, which infects rice panicles and forms dark green powdery spore masses on the grains (commonly known as "abundant harvest fruit").
The most prominent feature of this disease isThe window is extremely narrow.请提供需要翻译的中文段落。
Infection occurs from the pre-booting stage to the full heading stage.Pathogen spores invade the floral organs around the rice booting-to-heading stage; once infection is established, later fungicide applications are ineffective.
Symptom manifestation lags.After infection, diseased grains do not become visible until the late grain-filling stage, by which time fungicide application is already too late.
Therefore, the core of controlling rice false smut isHit the timing right.The optimal window is generally recognized as 5-7 days before the boot stage (panicle emergence). The timing should be determined based on field observation of panicle exsertion rather than the calendar.
The label states "before disease onset or at the early stage of disease onset." For rice false smut, "before disease onset" refers to the stage before panicle break.This is the most critical judgment to master regarding this product's use on rice.
IV. The Logic of One Dosage Managing Two Diseases
45-50 mL/mu, applicable to both diseases. Reason:
The toxicity of epoxiconazole to the two pathogens was similar.The sensitivity of Rhizoctonia solani and Ustilaginoidea virens to epoxiconazole is at the same order of magnitude, and registration trials confirmed that 45–50 mL/mu is effective against both.
The water consumption per mu is the same.The water volume for rice spraying is typically 30–45 kg per mu, and the application method is the same for both diseases.
However, the application sites differ.Although the dosage is the same, for sheath blight, the spray should target the base of the plant, while for rice false smut, it should target the panicle (spraying the panicle at the booting stage). In actual production, if both diseases need to be controlled simultaneously, spraying should cover both the upper and lower parts of the plant.
5. Pre-harvest interval: 30 days
Registration clarification:The safe pre-harvest interval for use on rice is 30 days, with a maximum of 2 applications per crop season.
The figure of 30 days means thatThe last application must be made more than 30 days before rice harvest.请提供需要翻译的中文段落。
It typically takes 30–45 days from the booting stage to harvest in rice. If pesticides are applied at the booting stage, the interval to harvest falls right at the margin of the pre-harvest interval. Therefore,The timing of this application at the booting stage must be carefully calculated.It is better to act early than late.
A maximum of 2 applications per season means that if both sheath blight and rice false smut need to be controlled, these are typically the two applications: one from late tillering to jointing stage (for sheath blight control), and one before panicle breakout (for rice false smut control).
VI. Precautions for the Use of Triazoles
Do not increase the dosage arbitrarily.The mechanism of action of triazoles determines that high doses can inhibit crop growth. Overapplication on rice may result in delayed heading and plant dwarfing.
Do not use a single product continuously for multiple consecutive seasons.Triazole resistance risk is relatively high, and cross-resistance exists among azole fungicides. Although alternative agents for rice are limited, rotation with fungicides of different modes of action (such as thifluzamide, validamycin, azoxystrobin, etc.) should still be adopted.
Do not stack two triazole fungicides in the same application.This will not enhance efficacy, but only accelerate resistance selection.