CYHALOFOP-BUTYL

Common name: Cyhalofop-butyl

Chemical name: butyl (R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propionate

Trade Name: Clincher(Brand name of Dow Chemical Company)

Molecular formula：C₂₀H₂₀FNO₄

Molecular structure：

Physical and chemical properties:

Molecular weight:357.4. Physical form: White crystalline solid. Density:1.172 (20 °C); Composition: Material is the resolved (R)- isomer. Melting point:50 °C; Vapour pressure:1.2×10-3 mPa (20 °C); Henry constant:9.51×10-4 Pa m3 mol-1 (calc.); Partition coefficient(n-octanol and water):logP = 3.31 (25 °C); Solubility: In water 0.44 (unbuffered),

0.46 (pH 5), 0.44 (pH 7.0) (all mg/l, 20 °C). In acetonitrile >250, n-heptane 6.06, n-octanol 16.0, dichloroethane >250, methanol >250, acetone >250, ethyl ac; Stability: Stable at pH 4, hydrolysed slowly at pH 7. At pH 1.2 or pH 9, decomposition is rapid.? 20°C: in acetonitrile, acetone, dichloroethane, methanol all >250 g/l; n-heptane 6 g/l; n-octanol 16 g/l.

Purity: 97%

Mode of actions:

Selective post-emergence control of 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.

Crop uses:

Rice.

Toxicology:

Oral: Acute oral LD50 for male and female rats, and for male and female mice >5000 mg/kg. Percutaneous: Acute percutaneous LD50 for male and female rats >2000 mg/kg. Inhalation: LC50 for rats >5.63 mg/l. ADI:0.02 mg/kg b.w.

Environmental profile

Ecotoxicology:

Algae:EC50 for Selenastrum capricornutum >1, Navicula sp. 0.64-1.33 mg/l. Soil and plant transformation products are less toxic to Selenastrum capricornutum. Bees: NOEC for honeybees >100 μg/bee. Birds: Acute oral LD50 for bobwhite quail and mallard ducks >5620 mg/kg. Dietary LC50 for bobwhite quail and mallard ducks >2250 ppm.Daphnia:LC50 >100 mg/l.Fish:LC50 for rainbow trout >0.49, bluegill sunfish 0.76 mg/l. These values are at or above the aqueous solubility of cyhalofop-butyl.Worms:LD50 (14 d) for earthworms >1000 mg/kg. Other aquatic spp.:EC50 for eastern oyster (Crassostrea virginica) 0.52, scud (Gammarus sp.) 0.81 mg/l. These values are at or above the aqueous solubility of cyhalofop-butyl.

Environmental fate:

Animals: Rats, dogs, ruminants and poultry readily metabolise cyhalofop-butyl by hydrolysis to the acid. Depending on the animal, the acid may also break down to other metabolites. The acid and any additional degradates are then rapidly excreted. Residue levels of Soil: Laboratory metabolism and field dissipation studies show that cyhalofop-butyl is rapidly metabolised in soil and sediment/water systems to cyhalofop acid; in the field, cyhalofop-butyl DT50 2-10 h in soil, <2 h in sediment/water.

WATER SOLUBILITY: 0.44 mg/l (unbuffered), 0.46 mg/l (pH 5), 0.44 mg/l (pH 7) (all at 20°C).

Bobwhite quail [8 d] LC50 >5,620 ppm Relatively non-toxic Rainbow trout [96 h] LC50 0.49 ppm Highly toxic

Daphnia magna [48 h] LC50 0.58 ppm Highly toxic

Bee [48 h, contact] LD50 >100 μg/bee Relatively non-toxic Mallard duck [8 d] LC50 >5,620 ppm Relatively non-toxic Oyster [96 h] LC50 0.52 ppm Moderately toxic Bluegill sunfish [96 h] LC50 0.76 ppm Highly toxic Earthworm LD50 >1,000 mg/kg

Fate in :

The EU SCP found that ground applications of cyhalofop-butyl to flooded or drained paddy fields at a maximum rate of 300 g ai/ha are unlikely to pose an unacceptable risk to aquatic organisms in adjacent surface water. In field studies, cyhalofop-butyl residues were below detection limits within 10 hours after application. However, all aerial applications and applications to flooded fields may pose an unacceptable risk to aquatic organisms in the paddy field. Additionally, no unacceptable risk to bees was observed, although there remains some uncertainty with other non-target arthropods which has yet to be addressed.

The EPA Fact Sheet advises not to use cyhalofop-butyl in areas where soils are permeable or where the water table is shallow, as this can result in water contamination. Fate in soil:

It has a low mobility in soils (Koc 1581- 6170 ml/g) whilst cyhalofop acid, the major soil metabolite, is more mobile. Cyhalofop-butyl is rapidly degraded under both aerobic and anaerobic conditions to give several metabolites. Soil metabolism is a significant route of dissipation with cyhalofop-butyl having T < 4 h and the major soil metabolite (cyhalofop acid) having T < 1 day. The parent compound and its metabolites do not penetrate below 15 cm depth of soil.

Cyhalofop-butyl is not expected to accumulate or leach into ground water. Fate in aqueous systems:

Cyhalofop-butyl is stable to hydrolysis at pH 5, has a half-life of 88 days at pH 7 but is rapidly hydrolysed at pH 9 (DT50 0.5 day).

The estimated environmental concentrations (EEC) of cyhalofop-butyl were determined using the SCI-GROW model and a model developed by the US EPA as the usual GENEEC model is not suitable for pesticide applications to rice. For the acute exposure scenario, the EEC is 36 ppb in a water-seeded paddy, and 25 ppb for surface water and 0.16 ppb for ground water in dry-seeded paddy. In calculation of the DWLOC (drinking water levels of comparison), an appropriate endpoint could not be identified and therefore cyhalofop-butyl is not expected to pose an acute risk. For chronic exposure, the EEC is 3.7 ppb for water-seeded rice and 2.6 ppb for dry-seeded rice. As the chronic DWLOC (350 ppb) is greater than the EEC, cyhalofop-butyl is not expected to pose a risk.

Transportation information:

Hazard Class: O (Obsolete as pesticide, not classified)

Other products:

Straight formulated products: Cyhalofop-butyl 10%, 20% EC; Cyhalofop-butyl 10%, 12%, 15% EW; Cyhalofop-butyl 30% OD.

Mixtures:

Penoxsulam + cyhalofop-butyl Pyribenzoxim + cyhalofop-butyl Cyhalofop-butyl + Bispyribac-sodium