What are the remedial methods for herbicide phytotoxicity?
How should weeds be controlled in rapeseed fields? Please advise. To control weeds in rapeseed fields, on the basis of vigorously implementing crop rotation such as rapeseed-rice, rapeseed-vegetable, and rapeseed-bean, and strengthening field management, we must vigorously promote chemical weed control technology. Pre-sowing chemical stubble cleaning: during the fallow period after rice harvest and before rapeseed sowing or transplanting, use glyphosate, bai...
How should herbicide phytotoxicity be remedied? Seeking advice1. Triazine herbicides
1. Application technology
(1) Target weeds: Triazine herbicides mainly control annual weeds and perennial weeds propagated by seed. Among annual weeds, they are better at controlling dicotyledonous weeds than grass weeds. Among triazine herbicides, only the methoxy-triazine herbicides can control some perennial weeds. Triazine herbicides mainly kill weed seedlings, so they should be applied after crop planting and before weed emergence. Although some herbicide varieties can also be applied post-emergence, they should be used when the weeds are at a young stage. (2) Dosage and application timing: The application rate should depend on soil texture and application time. Varieties such as atrazine and simazine among triazine herbicides have a long residual effect and are likely to cause phytotoxicity to subsequent crops, so in production they must be used according to the instructions or under the guidance of technical departments. Among soil characteristics, the ones that most affect the activity of triazine herbicides are soil organic matter and clay content. In soils with high clay and organic matter content, simazine can reduce plant toxicity. Soil pH is also an important factor affecting the herbicidal effect of triazine herbicides. However, soil pH has little effect on atrazine; under any conditions, atrazine is relatively safe for corn.
2. Remedial measures for phytotoxicity
Triazine herbicides are highly selective and safe for a few crops such as corn, but are prone to cause phytotoxicity to other crops. Phytotoxicity from this class of herbicides is mainly prevented through safe application technology. After phytotoxicity occurs, different remedial measures should be taken depending on the degree of phytotoxicity. When phytotoxicity is mild, crops can recover in a short period by strengthening fertilizer and water management and spraying sodium bisulfite, brassinolide, sodium nitrophenolate, etc.; for plots with severe phytotoxicity, deep plowing and irrigation should be carried out promptly, and then crops insensitive to this class of herbicides should be replanted.
2. Amide herbicides
1. Application technology
(1) Target weeds: Most varieties of amide herbicides mainly control annual grass weeds and some broadleaf weeds, and have very poor efficacy against perennial weeds. Chloroacetamide herbicides, such as acetochlor, alachlor, metolachlor, and butachlor, are soil treatment agents and are specific chemicals for controlling grass weeds. N-phenyl-DI-alanine types, such as neburon, metofluthrin, and isopropalin, are foliar treatment agents. They are specific chemicals for controlling wild oats in wheat fields. Propanil is a foliar treatment agent and can also be used to control barnyardgrass in paddy fields. Naphthoxyamine can be used to control broadleaf weeds and sedges in paddy fields, but is ineffective against barnyardgrass. (2) Dosage and application timing: Among chloroacetamide herbicides, acetochlor has the highest herbicidal activity. It is suitable for soils with high organic matter content. Usually under high temperature and high soil moisture conditions, the herbicidal effect is best, and the dosage can be appropriately reduced; at low temperatures the effect is poorer, and the dosage should be increased. Propanil, butachlor, and naphthoxyamine are mainly used for weed control in paddy fields. Propanil is very safe for rice. When applying it, whether in rice seedling fields, direct-seeded fields, or transplanted fields, thorough drainage must be carried out before spraying. While ensuring even spraying, appropriately increasing the water volume will give a better effect on controlling barnyardgrass. l---2 days after spraying, the water layer can be deepened, with the standard being to submerge the heart leaves of barnyardgrass. Neburon, metofluthrin, and isopropalin have specific efficacy against wild oats and cause no phytotoxicity to wheat. Applying them at high temperatures and when wild oats are growing vigorously gives a good herbicidal effect.
2. Remedial measures for phytotoxicity
Amide herbicides are relatively safe for crops, but for phytotoxicity caused during production due to excessive dosage or adverse environmental conditions, corresponding remedial measures should be taken according to different situations. After crop sowing and before emergence, if rainfall or flood irrigation occurs after application, crops are prone to phytotoxicity. Under normal circumstances, the symptoms of phytotoxicity can disappear after 15 days, and no remedial measures are needed. If irrigation and nitrogen fertilizer application continue during this period, phytotoxicity is often aggravated. For crops in some waterlogged areas, phytotoxicity may be more severe, and they should be replanted promptly, with the sowing depth appropriately increased.
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