Common name: Oxadiargyl

Chemical name:

5-tert-butyl-3-(2,4-dichloro-5-propargyloxyphenyl)-1,3,4-oxadiazol-2(3h)-one ol-2(3h)-one;

3-[2,4-dichloro-5-(2-propynyloxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2(3H)-one

Other names： Fenax, Topstar

Molecular formulae: C₁₅H₁₄Cl₂N₂O₃

Chemical structure:

Physical and Chemical Properties

Molecular weight:341.2; Physical form: White to beige powder, with no characteristic odour. Density:1.484 (20 ℃); Melting point:131℃; Vapour pressure:2.5 × 10-3 mPa (25℃); Henry constant:9.1 × 10-4 Pa m3 mol-1 (calc.); Partition coefficient(n-octanol and water): logP = 3.95; Solubility: In water 0.37 mg/l (20 ℃).; Stability: Stable to heat (15 d, 54 ℃), to light and in water. Stable to aqueous hydrolysis at pH 4, 5 and 7; DT50 7.3 d (pH 9).

Purity: 95%

Uses:

Biochemistry Protoporphyrinogen IX oxidase inhibitor. Mode of action Selective herbicide, active mainly pre-emergence; effects begin at germination. It is not absorbed by the plant. Efficacy is not dependent on soil texture and type. Uses Pre-emergence and early post-emergence herbicide active on broad-leaved weeds (Amaranthus, Bidens, Chenopodium, Malva, Monochoria, Polygonum, Portulaca, Potamogeton, Raphanus, Solanum, Sonchus, Rotala), grasses (Echinochloa, Leptochloa, Brachiaria, Cenchrus, Digitaria, Eleusine, Panicum and wild rice) and annual sedges, in rice (at 50-150 g/ha), upland crops (sunflower, potato, vegetables and sugar cane, at 300-500 g/ha) and perennial crops (fruit trees and citrus, at 500-1500 g/ha).

Mode of actions:

Herbicide.Oxadiargyl is applied pre-emergence of weeds. The emerging shoots of weeds come into contact with soil-bound oxadiargyl and growth ceases. Oxadiargyl can be used early post-emergence in rice although if later applications are to be made, the herbicide must be mixed with propanil. Oxadiargyl has limited activity against broadleaf weeds present in sugar cane. The company recommends mixtures with diuron or a triazine herbicide to control these weeds. The company notes that oxadiargyl can prevent the regrowth of certain perennial weeds.

In sunflowers, Oxadiargyl is sold in France in combination with Aclonifen (150 g ai/ha Oxadiargyl + 2000 g ai/ha Aclonifen). The product is recommended for application post-seeding and pre-emergence of the crop for the control of key annual grasses and broadleaf weeds (Amaranthus retroflexus, Chenopodium abum, Mercurialis annua, Solanum nigrum.)

Field trials in Brazil (Scientia Agricola, 1999) were conducted in irrigated rice sown in drained fields. Applied pre-emergence, Oxadiargyl provided excellent control of the sedge, Cyperus iria at 320 g ai/ha and the grasses Echinochloa colonum and Ischaemum rugosum at 400 g ai/ha. Light phytotoxicity was observed on the rice at 480 g ai/ha but the symptoms had disappeared by 60 days after treatment.

Field trials on vegetables were reported at the 14th conference of the Israel WSS. Oxadiargyl was applied 2 months prior to transplanting of crops and was activated by rainfall. The 500-800 g ai/ha dose rates provided good pre-emergence control of Malva nicaeensis, Lavatera spp,Urtica urens, Lamium amplexicaule, Amaranthus spp, Portulaca oleracea, Sinapis spp, Solanum nigrum, S villosum, Phalaris spp, Avena sterilis, Echinochloa spp and Digitaria sanguinalis over a period of 2-3 months. The 600 g ai/ha dose rate was selective to transplanted cabbage, cauliflower, broccoli and tomato. Garlic tolerated the 800 g ai/ha rate while watermelon tolerated the 1000 g ai/ha rate. Sown onions showed no yield decrease at the 500 g rate.

Oxadiargyl at 600-800 g ai/ha can be applied to processing tomatoes to provide residual control of Amaranthus spp and Solanum nigrum.

Field trials conducted in full stand potato plots and potatoes grown in the interrows of sugar cane (AMAS, 2001) showed that Oxadiargyl, applied at rates above 300 g ai/ha, was comparable to the commercial reference, Metribuzin, applied at 1000 g ai/ha. Oxadiargyl provided superior control of Solanum nigrum and Panicum subalbidum. No phytotoxic effects were observed on the crop.

CropUses: fruits, rice, sugar cane, sunflowers, plantations, potatoes, tomatoes, turf, vegetables.

Toxicology:

Acute toxicity

Oral: Acute oral LD50 for rats :5000 mg/ kg.

Percutaneous: Acute percutaneous LD50 for rabbits:2000 mg/kg. Not a skin irritant; minimal eye irritation (rabbits).

Inhalation:LC50 (4 h) for rats :5.16 mg/l.

Environmental Profile

Ecotoxicology:

Algae: EC50 (120 h) for Selenastrum capricornutum:1.2μg/l. Bees: LD50(oral and contact):200μg/bee.

Birds: Acute oral LD50 (14 d) for quail :;2000 mg/kg. Dietary LC50 (8 d) for quail and mallard ducks:5200 ppm. Daphnia: Not toxic at limit of water solubility.

Fish: Not toxic at limit of water solubility. Worms: Non-toxic at 1000 mg/ kg. Environmental fate:

Animals: Studies on goats and hens demonstrated that Oxadiargyl is rapidly excreted; there is no evidence of accumulation in milk, eggs or edible tissues. Soil: DT50 (lab., aerobic) 18-72 d (20-30 °C), forming two major metabolites (one of which is herbicidal) which are, in turn, steadily degraded, resulting in mineralisation to CO2 and a soil-bound residue.

Bobwhite Quail:LD50:2,000 mg/kg;

Fate in soil:

Oxadiargyl has a soil half-life of around 40 days. It has low soil mobility and is not expected to leach to ground water. WATER SOLUBILITY: 0.37 mg/l at 20℃.

Transportation Information:

Hazard Class: O (Obsolete as pesticide, not classified).

Other products:

Straight Formulated Products:

Type Content

Granule (GR) 0.5 % (w/w)

Water-dispersible granule (WG) 80% (w/w)

Wettable powder (WP) 80% (w/w)

Suspension concentrate (SC) 40% (w/v);80% (w/v)

Emulsifiable concentrate (EC) 3% (w/v);6% (w/v)

Mixtures:

Emulsifiable concentrate, suspension concentrate, water dispersible granule, wettable powder.