CAPTAN
IDENTIFICATION
Common name: Captan
Other name: captan (BSI, E-ISO, JMAF); captane ((m) F-ISO); captab (Republic of South Africa)
Iupac name: N-(trichloromethylthio)cyclohex-4-ene-1,2-dicarboximide
Chemical abstracts name: 3a,4,7.7a-tetrahydro-2-[(trichloromethyl)thio]-1H-isoindole -1,3(2H)-dione
Type: Fungicide
CAS RN: [133 06 2]
M.F.: C9H8Cl3NO2S
Mol Wt: 300.6
PHYSICAL CHEMISTRY
Form (appearance): Colourless crystals. Tech. is a colourless to beige amorphous solid, with a pungentodour.
Composition: Tech. is 90-95% pure.
M.P.: 178℃(tech., 175 178℃)
V.P.: < mPa>
S.G.: 1.74 (26℃)
Solubility.: In water 3.3 mg/l (25℃). In xylene 20. chloroform 70. acetone 21, cyclohexanone 23, dioxane 47, benzene 21, toluene 6.9, isopropanol 1.7, ethanol 2.9, diethyl ether 2.5 (all in g/kg, 26℃). Insoluble in petroleum oils.
Stability: Hydrolysed slowly at neutral pH, rapidly in alkali. Thermal DT50 >4 y (80℃), 14.2 d (120℃).
Henry: <1.18 × 10-1 Pa m3 mol-1 (calc.)
KowlogP: 2.8(25℃)
APPLICATION
Formulation types: DP; DS; WG; WP; WS; Seed treatment.
Biochemistry: Non-specific thiol reactant, inhibiting respiration.
Mode of action: Fungicide with protective and curative action.
Uses: Control of a wide range of fungal diseases, e.g. scab, Gloeosporium and other rots of pome fruit; shot hole of stone fruit; peach leaf curl; brown rots of cherries, apricots, peaches, plums, and citrus fruit; downy mildew and black rot of vines; early and late blights of potatoes and tomatoes; Alternaria blight and leaf spot of carrots; anthracnose and downy mildew of cucurbits; leaf spot diseases of ornamentals; anthracnose and leaf spot diseases of tomatoes; brown patch on turf; Botrytis spp. on many crops; etc. Used on a large number of other crops. Used as a seed treatment or root dip for control of Pythium, Phoma, Rhizoctonia spp., etc. on maize, ornamentals, vegetables, oilseed rape, and other crops.
Phytotoxicity: Non-phytotoxic if used as directed, but some varieties of apple (e.g. Red Delicious, Winesap) and pear (e.g. D`Anjou, Bosc) may be injured, as also may lettuce seeds and, at higher dosages, celery and tomato seeds.
Compatibility: Incompatible with alkaline materials, oil sprays, TEPP, and emulsifiable concentrate formulations of parathion.
MAMMALIAN TOXICOLOGY
Reviews: FAO/WHO 74, 76 (see part 2 of the Bibliography).
IARC ref. 30; class 3
Oral: Acute oral LD50 for rats 9000 mg/kg.
Skin and eye: Acute percutaneous LD50 for rabbits >4500 mg/kg. Corrosive to eyes: mild skin irritant (rabbits).
Inhalation: LC50 for male rats >0.72, female rats 0.87 mg/l (tech.). Dust may cause respiratory irritation.
Noel: (2 y) for rats 2000, dogs 4000 mg/kg diet. No carcinogenic, teratogenic, or mutagenic effects observed.
ADI: (JMPR) 0.1 mg/kg b.w. [1995].
Toxicity: WHO (a.i.) III (Table 5); EPA (formulation) IV
EC hazard: R40L Xl; R361 R43
ECOTOXICOLOGY
Birds: Acute oral LD50 for mallard ducks and pheasants >5000, bobwhite quail 2000-4000 mg/kg. Not toxic to starlings or red winged blackbirds at 100 mg/kg.
Fish: LC50 (96 h) for bluegill sunfish 0.072, harlequin fish 0.3, brook trout 0.034 mg/l.
Daphnia: LC50 (48 h) 7-10 ppm.
Other aquatic spp. Moderately toxic to aquatic invertebrates.
Worms: Bees: ED50 (oral) 91 Hg/bee; (contact) 788 μg/bee.
ENVIRONMENTAL FATE
Animals: In mammals, the three chlorine atoms are cleaved under the influence of cellular sulfhydryl compounds. Trithiocarbamate, thiophosgene, and tetrahydrophthalimide are formed (R. G. Owens, Ann. New York Acad. Sci., 1969, 160, 114 132).
Soil/Environment: Soil Kd 3-8 (pH 4.5-7.2, o.m. 2.2-6.7%); DT50 c. 1 d (25℃, pH 7.2, o.m. 1.2%).
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