Many types of chloroacetanilide herbicides, their uses explained clearly in one go

Most “chloroacetanilide” herbicides on the market are amide herbicides, mostly soil treatment agents, mainly applied after crop sowing and before emergence. They have good control effect on annual grass weeds, poor control effect on broadleaf weeds; under normal circumstances the control effect is acetochlor > metolachlor = propisochlor > butachlor > alachlor > propachlor.

Acetochlor: residual period 40-70 days. It is mainly retained in the 0-3cm soil layer; under high temperature and high humidity, or after application under sustained low temperature and high humidity, it easily causes phytotoxicity, but under normal circumstances it can recover to normal after 10-15 days. Application 24-72 hours after sowing easily causes phytotoxicity. The main part absorbed by weeds is the bud, so it must be applied before the weeds emerge.

Metolachlor: residual period 30-35 days, and its activity naturally disappears 10-12 weeks after application. Monocotyledonous grass weeds mainly absorb it through the coleoptile, while dicotyledonous weeds absorb it through the young bud and young root, conducting it upward, inhibiting the growth of young buds and fine roots; susceptible weeds die from poisoning after germination but before emergence or just as they emerge. The absorption capacity of grass weeds is stronger than that of broadleaf weeds. Application 3-5 days before transplanting is preferable; in direct-seeded fields, apply 1-2 days after sowing before emergence. This agent is easily degraded by soil microorganisms, and its residual period is medium.

Alachlor: generally controls weeds for about 60 days. It can be adsorbed by soil, is not easily leached, and is not easily lost by volatilization. Rice, sorghum, millet, cucumber, Chinese chive, and spinach crops are very sensitive to it. The depth of soil incorporation should preferably not exceed 5cm.

Pretilachlor: residual period in paddy fields is 30-50 days. When used alone, it can only be used in transplanted rice fields; when used in seedling fields or direct-seeded fields, it harms the seedlings. But adding a safener can make up for the deficiency; when the application rate is too large, the young leaves and leaf tips to leaf margins of the seedlings become chlorotic and curled, and plant growth is inhibited.

Ketochlor: residual period about 40 days. Cucumber is very sensitive to it, and its safety is worse than butachlor, so it is not suitable for application in rice seedling fields, direct-seeded fields, and small seedlings, weak seedlings, or leaking paddy fields.

Napropamide: half-life as long as 12 weeks. It is effective when applied before emergence or at the 1-leaf stage after emergence. Wheat among grasses, Chinese chive among Liliaceae, and celery, fennel, and lettuce among Apiaceae are sensitive to it.

Propanil: used in paddy fields, it decomposes quickly in soil. It is a highly selective contact herbicide that does not translocate and only acts at the contact site, and is used only as a foliar treatment agent. Rice must not be treated within 10 days before or after spraying; it must not be mixed with 2,4-D, nor used together with liquid fertilizers.

Sachlor: residual period about 60 days. After application, maintain a shallow water layer for 5-7 days; do not drain, and do not conduct cross-irrigation. It is suitable for application in plastic-film mulched fields, irrigated fields, summer crops, and dry fields in southern China; rice young buds are very sensitive to it.

Butachlor: residual period about 60 days. It is effective against weeds that are germinating and before the 2-leaf stage. In seedling fields, application 3 days after sowing gives good weed control; before or after that the control effect is average, and application too early easily causes phytotoxicity. Water must not submerge the rice heart.

Propisochlor: residual period 60-80 days, safe for succeeding crops. It is ineffective against perennial grass weeds and broadleaf weeds. This agent is suitable for application in plastic-film mulched fields, irrigated fields, summer crops, and dry fields in southern China; rice young buds are very sensitive to it.

Diphenamid: long residual period. After application, wheat and other crops can only be planted after 1 year; it can only kill weeds before emergence.

Mefenacet: residual period more than 1 month, used in paddy fields. It has a special effect on barnyardgrass; apply 3-10 days after rice transplanting, keep a water layer of 3-4cm, and do not apply at the rice seedling stage, especially not at the seedling stage.

Diflufenican: half-life in soil is 16-20 weeks, and it can control various weeds in wheat fields.