NOMENCLATURE
Common name boscalide( (m) F-ISO); boscalid (BSI, E-ISO)
IUPAC name 2-chloro-N-(4′-chlorobiphenyl-2-yl)nicotinamide
Molecular structure
Chemical Abstracts name 2-chloro-N-(4′-chloro[1,1′-biphenyl]-2-yl)-3-pyridinecarboxamide
CAS RN [188425–85–6]
PHYSICAL CHEMISTRY
Mol. wt. 343.2
M.f. C18H12Cl2N2O
Form White odourless crystals.
M.p. 142.8–143.8 °C
V.p. 7.2 × 10-4 mPa (20 °C)
Kow logP = 2.96
Henry 5.178 × 10-5Pa m3 mol-1
S.g./density 1.381 (20 °C)
Solubility In water 4.6 mg/l (20 °C). In n-heptane <10, methanol 40–50, acetone 160–200 (all in g/l, 20 °C).
Stability Stable to hydrolysis at pH 4, 5, 7 and 9; stable to aqueous photolysis.
APPLICATIONS
Biochemistry SDHI: inhibits succinate ubiquinone reductase (also known as complex II), in the mitochondrial electron transport chain.
Mode of action Foliar fungicide, with translaminar and acropetal movement within the plant leaf, providing preventive and, in some cases, curative action. Inhibits spore germination, germ tube elongation and is also effective on all other stages of fungal development.
Uses For control of powdery mildews, Alternaria spp., Botrytis spp., sclerotinia spp., Mycosphaerella spp., and Monilinia spp. on grapes, turf, and a range of fruit, vegetables and ornamentals. Also used in mixture in arable crops, including cereals, rape, peanuts and potatoes.
Formulation types SC; WG.
ENVIRONMENTAL FATE
Animals Hydroxylation of the biphenyl ring, subsequent glucuronidation and sulfatationreactions. The systemically available portion of a.i. is rapidly and extensively metabolised, with rapid excretion, mainly via faeces.
Plants Hydroxylation in the biphenyl and pyridine rings, and cleavage reactions in both rings, were observed. However, unchanged parent formed the major part of the residue. Soil/Environment Moderate degradation behaviour in soil; soil DT50 108 d to >1 y (lab., aerobic conditions, 20 °C); field DT50 28 d to c. 200 d. Good degradation in natural water/sediment systems.
MAMMALIAN TOXICOLOGY
Oral Acute oral LD50 for rats >5000 mg/kg.
Skin and eye Acute dermal LD50 for rats >2000 mg/kg. Not a skin or eye irritant (rabbits). Not a skin sensitiser (guinea pigs).
Inhalation LC50 (4 h) for rats >6.7 mg/l.
NOEL for rats c. 5 mg/kg b.w.; chronic NOAEL 21.8 mg/kg b.w..(EPA Fact Sheet).ADI (JMPR) 0.04 mg/kg b.w. [2006]; (EC) 0.04 mg/kg b.w. [2008]; (EPA) no acute endpoint identified; cRfD 0.218 mg/kg b.w. [2003]; (FSC) 0.044 mg/kg b.w. [2006]. Other Non-mutagenic (Ames, mice), non-teratogenic (rats, rabbits), non-carcinogenic (dogs, rats, mice); no adverse effects on reproduction (rats).
ECOTOXICOLOGY
Birds LD50 for bobwhite quail >2000 mg/kg b.w.
Fish LC50 (96 h) for rainbow trout 2.7 mg/l.
Daphnia EC50 (48 h) 5.33 mg/l.
Algae ErC50 (96 h) for Pseudokirchneriellasubcapitata 3.75 mg/l.Other aquatic spp. NOEC for Chironomusriparius 2.0 mg/l.
Bees NOEC (oral) 166 µg/bee; (contact) 200 µg/bee.
Worms LC50 for Eiseniafoetida>1000 mg/kg dry soil.
