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Thiabendazole

NOMENCLATURE
Common name thiabendazole (BSI, E-ISO, (m) F-ISO, BAN, JMAF)
IUPAC name 2-(thiazol-4-yl)benzimidazole; 2-(1,3-thiazol-4-yl)benzimidazole
Chemical Abstracts name 2-(4-thiazolyl)-1H-benzimidazole
CAS RN [148-79-8] EEC no. 205-725-8 Development codes MK 360 (Merck)

APPLICATIONS
Biochemistry Inhibits mitosis by binding to tubuline and thus severely impairs fungal growth and development Mode of action Systemic fungicide with protective and curative action. Thiabendazole forms a protective deposit on the treated surface of fruit and tubers. Uses As a mainly post-harvest fungicide for the control of Aspergillus, Botrytis, Ceratocystis, Cercospora, Cladosporium, Colletotrichum, Corticium, Diaporthe, Diplodia, Fusarium, Gibberella, Gloeosporium, Oospora, Penicillium, Phoma, Rhizoctonia, Sclerotinia, Septoria, Thielaviopsis, Verticillium spp., etc., in avocados, bananas, chicory, citrus fruit, some cucurbits, mangoes, mushrooms, ornamentals, pome fruit, potatoes, strawberries and other crops. Also used for foliar application (on fruits and vegetables), seed treatment and stem injection application. Formulation types SC; SL; TB; WP. Compatibility Incompatible with copper products and oxidising agents such as chlorates and nitrates. Selected tradenames: 'Mertect' (post-harvest, foliar) (Syngenta); 'Storite' (post-harvest) (Syngenta); 'Tecto' (post-harvest, foliar) (Syngenta); 'Decco' (post-harvest) (Cerexagri); 'LSP' (Gustafson); mixtures: 'Vincit' (+ flutriafol+ imazalil) (Cheminova)

OTHER TRADENAMES
'Hykeep' (Agrichem Int.); (post-harvest) (Xeda) mixtures: 'Apron Combi' (+ metalaxyl+ thiram) (seed) (Syngenta); 'Extratect ' (+ imazalil) (seed) (Syngenta); 'Storite SS' (+ tecnazene) (post harvest) (Syngenta); 'Ferrax' (+ ethirimol+ flutriafol) (seed) (Syngenta, Cheminova); 'Fortiva' (+ metalaxyl+ thiram) (seed) (Limagrain); 'Hytec Super' (+ tecnazene) (Agrichem Int.); 'Hy-TL' (+ thiram) (Agrichem Int.) Discontinued names: 'Radinex' * (BASF)

ANALYSIS
Product analysis is by hplc. Residues in food crops determined by hplc or spectrofluorimetrically. Details are available from Syngenta

MAMMALIAN TOXICOLOGY
Reviews MAFF Report No. 54 (1992); JECFA 48 (Geneva, 1997; see part 2 of Bibliography), JMPR 1997 (Lyon). Oral Acute oral LD50 for mice 3600, rats 3100, rabbits 3800 mg/kg. Skin and eye Acute dermal LD50 for rabbits >2000 mg/kg. Non-irritating to eyes and skin (rabbits). Not a skin sensitiser (guinea pigs). Inhalation LC50 for rats >0.5 mg/kg. NOEL In 2 y feeding trials, rats receiving 40 mg/kg daily showed no ill-effects. ADI (JECFA) 0.1 mg/kg b.w. [1997]. Toxicity class WHO (a.i.) III (Table 5); EPA (formulation) III

ECOTOXICOLOGY
Birds Acute oral LD50 for bobwhite quail >2250 mg/kg. Dietary LC50 (5 d) for bobwhite quail and mallard ducks >5620 mg/kg diet. Fish LC50 (96 h) for bluegill sunfish 19, rainbow trout 0.55 mg/l. Daphnia EC50 (48 h) 0.81 mg/l. Algae EC50 (96 h) for Selenastrum 9 mg/l; NOEC for Selenastrum 3.2 mg/l. Other aquatic spp. LC50 (96 h) for shrimps 0.34 mg/l, oysters >0.26 mg/l. Bees Not toxic to bees. Worms LC50 >500 mg/kg soil.

ENVIRONMENTAL FATE
Animals When administered orally, thiabendazole is rapidly absorbed; up to 90% of the total dose is eliminated (about 65% in urine and 25% in faeces) within 24 h, in both sexes. The compound is rapidly distributed to tissues, with highest levels found in the heart, lungs, spleen, kidneys, and liver. The compound is essentially completely cleared from the body within 7 days in both dose groups. Thiabendazole undergoes hydroxylation at the 5-position. Plants The residue on all crops treated pre- or post-harvest is parent thiabendazole. Soil/Environment Soil DT50 33 d (20 °C, 40% MWC, 0.1 mg a.i./kg soil), 120 d (20 °C, 40% MWC, 1 mg a.i./kg soil). Aqueous photolysis DT50 29 h (pH 5).