Common name: thiabendazole

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]

 

Mol. wt.: 201.3; M.f.: C10H7N3S; Form: Off-white powder. M.p.: 297-298 °C. V.p.: 4.6x10-4 mPa (25 °C). KOW: logP = 2.39 (pH 7). Henry: 2.7x10-8 Pa m3 mol-1 S.g./density: 1.3989; Solubility: In water 0.16 (pH 4), 0.03 (pH 7), 0.03 (pH 10) (all in g/l, 20 ºC). In n-heptane <0.01, xylene 0.13, methanol 8.28, 1,2-dichloroethane 0.81, acetone 2.43, ethyl acetate 1.49, n-octanol 3.91 (all in g/l, 20 ºC). Stability: Hydrolytically stable; aqueous photolysis DT50 29 h (pH 5). pKa: pKa1 4.73, pKa2 12.00

 

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.

 

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: 0.1 mg/kg b.w.

Toxicity class: WHO (a.i.) III (Table 5); EPA (formulation) III

 

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.

 

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).