Fungicide

FRAC  16; MBI: reductase

NOMENCLATURE

Common name tricyclazole (BSI, E-ISO, (m) F-ISO, ANSI)

IUPAC name 5-methyl-1,2,4-triazolo[3,4-b][1,3]benzothiazole 

Chemical Abstracts name 5-methyl-1,2,4-triazolo[3,4-b]benzothiazole 

CAS RN [41814-78-2]  EEC no. 255-559-5  Development codes EL-291 (Lilly) 

PHYSICAL CHEMISTRY

Mol. wt. 189.2  M.f. C9H7N3S  Form Crystalline solid.  M.p. 187-188 ºC  B.p. 275 °C  V.p. 0.027 mPa (25 ºC)  KOW logP = 1.4  Henry 3.19 ´ 10-6 Pa m3 mol-1 (calc.)  Solubility In water 1.6 g/l (25 ºC). In acetone 10.4, methanol 25, xylene 2.1 (all in g/l, 25 ºC).  Stability Stable at 52 ºC (highest storage temperature tested). Relatively stable to u.v. light. 

COMMERCIALISATION

History Fungicide reported by J. D. Froyd et al. (Phytopathology, 1976, 66, 1135). Introduced in Philippines (1976) by Eli Lilly & Co. (agrochemical interests now Dow AgroSciences).  Patents GB 1419121  Manufacturers Dow AgroSciences; Nagarjuna Agrichem

APPLICATIONS

Biochemistry Melanin biosynthesis inhibitor (reduction of 1,3,8-trihydroxynaphthalene and vermelone).  Mode of action Systemic fungicide, absorbed rapidly by the roots, with translocation through the plant.  Uses Control of rice blast (Pyricularia oryzae) in transplanted and direct-seeded rice. Can be applied as a flat drench, transplant root soak, or foliar application. One or two applications by one or more of these methods give a season-long control of the disease.  Formulation types DP; GR; SC; WG; WP.  Selected tradenames: 'Beam' (Dow AgroSciences); 'Sazole' (Sanonda)

OTHER TRADENAMES

'Blas-T' (Crystal) mixtures: 'Beam Admire' (+ imidacloprid) (Japan) (Nihon Bayer)

ANALYSIS

Product analysis by glc with FID or by hplc (E. W. Day et al., Anal. Methods Pestic. Plant Growth Regul., 1980, 11, 263). Residues in plant tissue determined by glc with FPD, the main metabolite (hydroxymethyl analogue) first being converted to a derivative (idem, ibid.). In drinking water, by gc with FID (AOAC Methods, 1995, 991.07). Details available from Dow AgroSciences. 

MAMMALIAN TOXICOLOGY

Oral Acute oral LD50 for rats 314, mice 245, dogs >50 mg/kg.  Skin and eye Acute percutaneous LD50 for rabbits >2000 mg/kg. Slight eye irritant; non-irritating to skin (rabbits).  Inhalation LC50 (1 h) for rats 0.146 mg/l air.  NOEL (2 y) for rats 9.6 mg/kg b.w., for mice 6.7 mg/kg b.w.; (1 y) for dogs 5 mg/kg b.w.; 3-generation reproduction for rats 3 mg/kg b.w.  ADI 0.03 mg/kg.  Toxicity class WHO (a.i.) II; EPA (formulation) II  EC hazard Xn; R22 

ECOTOXICOLOGY

Birds Acute oral LD50 for mallard ducks and bobwhite quail >100 mg/kg.  Fish LC50 (96 h) for bluegill sunfish 16.0, rainbow trout 7.3, goldfish fingerlings 13.5 mg/l.  Daphnia LC50 (48 h) >20 mg/l; NOEC (21 d) 0.96 mg/l. 

ENVIRONMENTAL FATE