Precautions for the Use of Common Rice Herbicides
In the process of rice production, the use of herbicides is quite common. The use of herbicides is closely related to the variety of rice and management methods. Let's learn together about the methods and precautions for using several common rice herbicides.
Precautions for the Use of Common Rice Herbicides
1. Butachlor
Butachlor is an excellent selective herbicide for upland crops, with wide applicability. It is widely used in the fields of corn, soybeans, peanuts, cotton, direct-seeded upland rice, potatoes, tobacco, and vegetables for weed control. It can prevent the growth of weed seedlings, effectively targeting annual grasses and some broadleaf weeds such as crabgrass, barnyard grass, goosegrass, foxtails, pigweed, purslane, amaranth, chenopodium, jimsonweed, barnyardgrass, watergrass, etc. The control effect on grassy weeds is better than broadleaf weeds, and its effectiveness on perennial weeds is poor. It is important to note that it can only be used once per crop season.
Butachlor is a selective pre-emergence and post-emergence herbicide for upland soil. Weeds absorb the herbicide through germinating buds, and the herbicide binds to microtubule proteins in the plant cells, inhibiting mitosis, thus causing weed death. For dry nursery beds and upland nursery beds: use 33% butachlor emulsion 150-200mL/acre, diluted in 15-20kg water, and spray the soil surface before seedling emergence.
Precautions:
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For soils with low organic matter content, sandy soils, low-lying areas, use low doses. For soils with high organic matter content, clay soils, dry climates, and low soil moisture content, use high doses.
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When soil moisture is insufficient or under dry climate conditions, mix the soil 3-5cm after application.
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It has strong adsorption in the soil and will not be leached into the deep soil after application. After rainfall, it not only does not affect the weeding effect but also improves the weeding effect, so there is no need to re-spray.
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The residual period in the soil is 45-60 days.
2. Pretilachlor
Pretilachlor belongs to the sulfonylurea herbicide class, which is a selective systemic herbicide. It is mainly absorbed by the roots of weeds, quickly transferred in the weed plants, inhibiting their growth, and causing gradual death. Rice can decompose the herbicide, so it has almost no effect on rice growth. It has stable efficacy, high safety, and a duration of 25-35 days. It is suitable for rice nurseries, direct-seeded fields, and transplanted fields. It can control both annual and perennial broadleaf weeds and sedge weeds, such as monochoria, water monochoria, Cyperus difformis, duckweed, water celery, Alternanthera philoxeroides, creeping smartweed, water pennywort, water dropwort, etc. It is usually used during the 1-3 leaf stage of rice, with a dosage of 15-30g/acre of 10% wettable powder mixed with soil for soil poisoning and spreading, or sprayed with water. Maintain a water layer for 3-5 days after treatment.
Precautions: Pretilachlor is safe for rice, but late-season rice varieties (indica and glutinous rice) are relatively sensitive. It is advisable to avoid applying it during late-season rice tillering to prevent phytotoxicity.
3. Bensulfuron-methyl
Bensulfuron-methyl is a selective systemic herbicide for rice fields. It is effective in controlling both annual and perennial broadleaf weeds and sedges. It can be absorbed by the roots and leaves of weeds and rapidly transferred to other parts of the plant. It is safe for rice and has flexible usage methods. For rice nurseries and direct-seeded fields, the herbicide can be applied from sowing to within 2-leaf stage of weeds. It can be used to control annual broadleaf weeds and sedges by spraying 20-30g/acre of 10% wettable powder mixed with 30kg of water or by spreading 20kg of fine moist soil. Maintain a water layer of 3-5cm for 3-4 days. For transplanted fields, it can be applied 3 weeks before or after transplanting, but it is best to apply it 5-7 days after transplanting. It can effectively control perennial weeds and also control barnyard grass by increasing the dosage to 30-50g.
Precautions: When mixed with MCPP, it produces better results. Bensulfuron-methyl has a good effect on weeds within the 2-leaf stage, but the effect is poor after the 3-leaf stage.
4. Propanil
Propanil, also known as propanil, is a highly selective herbicide for rice fields. It has a broad spectrum of weed control and is safe for rice. Propanil belongs to the acetanilide class of herbicides and is a cell division inhibitor. Weed seeds absorb the herbicide during germination, but root absorption is poor. It can only be used as a pre-emergence soil treatment and can control barnyard grass, monochoria, Cyperus iria, Cyperus rotundus, etc. It is usually used 3-5 days before transplanting. When used in direct-seeded rice fields, it is usually applied 2-4 days after sowing. Spray 100-115mL/acre of 30% emulsion or spread evenly with 20kg of fine clay soil, maintaining a shallow water layer for 3-4 days. To ensure early safety, propanil is often used with the safety agent CGA123407. It is suitable for controlling barnyard grass, crabgrass, pigweed, goosegrass, water pennywort, jimsonweed, water caltrop, duckweed, Cyperus difformis, and other annual grasses and broadleaf weeds.
Precautions:
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Land should be prepared and seeded promptly after application to avoid the emergence of weeds, affecting the efficacy.
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The rice seeds should have normal roots and buds when sown, and avoid sowing seeds with buds but no roots.
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When used in northern rice-growing areas, the timing of application should be appropriately extended. It is necessary to conduct trials before large-scale promotion to avoid phytotoxicity.
5. Quinclorac
Quinclorac is a systemic herbicide with internal absorption properties in rice fields. It can be absorbed by the roots and shoots of weeds, especially by the shoots. It has a wide application period but a narrow spectrum of weed control. It is suitable for controlling barnyard grass, water foxtail, and Cyperaceae. It can be applied before sowing in rice fields. After preparing the field and making seedling beds, use 96% emulsion 100-150mL/acre, mix with fine moist soil 10kg, and evenly spread it on the soil surface, then immediately mix and level the soil. Maintain a shallow water layer, and sow rice seeds that have been germinated and whitened for 2-3 days. After 2-3 days, drain the water naturally. It can also be used in rice seedlings with 3 leaves or more, and weeds with 2-3 leaves. Use 96% emulsion 100-150mL/acre mixed with fine moist soil 10kg, maintain a water layer of 4-5cm, and continue for 6-7 days.
Precautions:
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Quinclorac has strong volatility. Keep the water layer for 7 days during and after application to ensure efficacy.
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Japonica rice is sensitive to quinclorac. Excessive dosage or uneven application may cause phytotoxicity.
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Quinclorac is particularly effective against barnyard grass but ineffective against other broadleaf weeds and perennial rhizomatous weeds. To control a broader spectrum of weeds, it can be mixed with other herbicides.
6. Bentazon
Bentazon is a selective systemic herbicide for rice fields. It can be absorbed by the roots and shoots of weeds, especially by the sheaths. It has a wide application period and a narrow spectrum of weed control. It is suitable for controlling barnyard grass, monochoria, Cyperaceae, pigweed, barnyardgrass, water pennywort,
Cyperus difformis, water caltrop, and Alternanthera philoxeroides. It can be applied before or after sowing in direct-seeded rice fields. Use 50% emulsion 200-300mL/acre, mixed with 35kg water, and spray evenly. Maintain a water layer of 3-5cm for 5-7 days. In dry-seeded rice fields, apply 30-40kg of even spraying.
Precautions:
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Bentazon has good efficacy when mixed with quinclorac. It is particularly effective against barnyard grass and has little effect on rice.
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The weeds should be kept moist during and after spraying for 7 days to ensure the efficacy of the herbicide.
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In the northern rice-growing areas, the application period should be extended appropriately. Trials should be conducted before large-scale use to avoid phytotoxicity.