other name:butyl (R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoate
CAS No.: [ 122008-85-9 ]
Molecular Formula: C20H20FNO4
Cyhalofop-butyl is active following absorption through the leaves. Weed growth stops immediately and the most recent leaves become necrotic within a week. Death occurs within 2-3 weeks depending on the weather and the size of the weeds. Cyhalofop-butyl will not control broadleaf weeds as the biochemical mode of action is specific to certain grasses.
Cyhalofop-butyl does not present any useful pre-emergence activity. It can be applied from germination to the four-leaf stage of barnyard grass with granular formulations, and from germination to the six-leaf stage with liquid formulations. It is rainfast within 2-3 hours and has no residual activity. The US product label states that 2.3 L/ha of crop oil concentrate should be added to the tank for all treatments. The product poses low risk to nearby crops such as cotton, soybeans and vegetables but Dow advises that drift to more sensitive crops such as maize, nectarines, peaches, sugar cane and sorghum should be avoided.
The selectivity of rice to cyhalofop-butyl is due to rapid metabolism (half-life less than 10 hours) in this crop to the inactive dicarboxylic acid resulting from hydrolysis of the ester and nitrile groups. By contrast, the major initial metabolic step in susceptible grasses is the rapid formation of the herbicidally active monocarboxylic acid (80% formed within 10 hours) by hydrolysis of the ester group.
It is recommends that for dry-seeded rice, Clincher should be applied to 1-4 inch weeds pre-flood at a rate of 280 g/ha or post-flood at 280-312 g/ha for control of large grasses prior to heading. For water-seeded rice, the product should be applied when the weeds are at least 50% exposed, and the fields should be reflooded 24-48 hours after application if drained.
Cyhalofop-butyl has a better safety margin than Whip but may face use limitations in areas where Echinochloa is developing resistance to ‘fop’ herbicides such as Whip. However, it may be used in situations where propanil- or quinclorac-resistant Echinochloa is present. Application of Clincher at the three-leaf stage, followed by trichlopyr (Grandstand) at mid-tillering was found to provide broad spectrum control, whilst tank mixtures of cyhalofop and propanil were found to control Echinochloa spp, Cyperus compressus and Leptochloa chinensis.
Studies found that a tank mix of cyhalofop-butyl at 60-80 g ai/ha and ethoxysulfuron at 12 g ai/ha provided effective control against all common weeds present in rice fields such as Echinochloa crus-galli, E colona, Leptochloa chinensis, Cyperus difformis, Fimbristylis miliacea, Ludwigia octovalvis, L adscendens and Marsilea minutaI. A higher rate of cyhalofop-butyl, applied as a late post-emergence spot treatment at 160-200 g ai/ha, provided control of perennial weeds Paspalum distichum and Echinochloa stagmina while retaining good activity in the rice crop.
Fatty acid synthesis inhibitor, by inhibition of acetyl CoA carboxylase (ACCase). Selectivity between susceptible grasses and dicotyledonous plants is attributed to the forms of ACCase present and their compartmentalisation within plant cells. Susceptible grasses contain the susceptible eukaryotic form of ACCase; dicotyledonous plants contain both susceptible eukaryotic and herbicide-resistant prokaryotic forms of ACCase, rendering them resistant to cyhalofop-butyl. Rice tolerance to cyhalofop-butyl is due to rapid metabolism to the herbicidally inactive diacid (t1/2 <10 hr), whereas susceptible grasses metabolise cyhalofop-butyl to the herbicidally active monoacid.
Mode of action
Post-emergence herbicide with foliar uptake only and no soil activity. A systemic herbicide that is readily absorbed by plant tissue, is moderately phloem-mobile and accumulates in meristematic regions. Grass weeds cease growth immediately after treatment, with yellow patches appearing within 2-3 days to one week, leading to necrosis and death of the whole plant within 2 to 3 weeks. Uses For post-emergence control of grass weeds in rice. Applied at 75-100 g/ha in tropical rice and 180-310 g/ha in temperate rice.
Formulation types EC; EW; GR.
|Acetone Insoluble Matter||0.5% max.|
GHS complaint Safety Data Sheet (SDS) for commercial product of Cyhalofop butyl is available uopn requested.