Bentazone

Description

Bentazon is unique under these herbicides because it is the only compound that bears a sulfonyl group. A puzzle that is not solved yet is that bentazone is an excellent herbicide but has a very low pI50-value.

Chemical properties

Bentazon is a colorless to white crystalline powder.

The Uses of Bentazone

Herbicide.

The Uses of Bentazone

Selective, contact, postemergence herbicide used to control a variety of annual and perennial broad-leaved weeds in most grass and legume crops.

Definition

ChEBI: A benzothiadiazine that is 1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide substituted by an isopropyl group at position 3.

Agricultural Uses

Selective post-emergent herbicide: A post-emergence herbicide used to control broadleaf weeds in crops such as beans, corn, mint, soybeans, rice, and peanuts. All products formerly marketed in the U.S. contain the sodium salt of bentazon as the active ingredient, referred to as sodium bentazon. Also used in selective post-emergent control of broadlelaf weeds and sedges in alfalfa, asparagus, cereals, clover, digitalis, dry peas, flax, garlic, grasses, green lima beans, mint, onions, potatoes, snap beans for seed, sorghum, soybeans and sugarcane. Not currently registered in the U.S. It is reported to be used in most European countries.

Trade name

ASAGIO®; BAS 351-H®; BASAGRAN®; BENDIOXIDE®; BENTA®; BLAST®; ENTRY®; LADDOK®; LEADER®; PLEDGE®; STORM®

Safety Profile

Moderately toxic by ingestion and skin contact. An experimental teratogen. Other experimental reproductive effects. When heated to decomposition it emits very toxic fumes of SO, and NOx.

Potential Exposure

A potential danger to those involved in the manufacture, formulation or application of this selective postemergent thiadiazine herbicide.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seekmedical attention immediately. If this chemical contactsthe skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove fromexposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing hasstopped and CPR if heart action has stopped. Transferpromptly to a medical facility. When this chemical hasbeen swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

Environmental Fate

Soil. Under aerobic conditions, bentazone was reported to degrade to 6- and 8-hydrox ybentazone compounds. In addition, anthranilic acid and isopropylamide were reported as soil hydrolysis products (Otto et al., 1978). Persistence in soil is less than 6 weeks (Hartley and Kidd, 1987). Bentazone is readily adsorbed onto organic carbon and therefore, is not expected to leach to groundwater (Abernathy and Wax, 1973). The dissipation half life of bentazone in field soil is 5 days (Ross et al., 1989).
Plant. Undergoes hydroxylation of the aromatic ring and subsequent conju-gation in plants (Otto et al., 1978; Hartley and Kidd, 1987) forming 6- and 8-hydroxybentazone compounds (Otto et al., 1978). The half-life in and/or on plants is 2–3 days (
Photolytic. Humburg et al. (1989) reported that 30% degradation of bentazone on glass plates occurred when exposed to UV light (λ = 200–400 nm); however, no photoproduct(s) were reported. The natural sunlight and simulated sunlight irradiation of
Chiron et al. (1995) investigated the photodegradation of bentazone (20 μg/L) in distilled water and Ebro River water using an xenon arc irradiation. In distilled water, bentazone completely disappeared after 16 hours of irradiation. Photodegradation appeared to follow pseudo-first-order kinetics with a half-life of about 2.5 hours. The presence of humic substances (4 mg/L) increased the rate of photodegradation and the disappearance of bentazone was achieved in 8 hours. No significant breakdown photoproducts were identified.

Metabolic pathway

14C-Bentazon degrades in soils under conventional tillage and no-tillage (3-18 years) with varying histories of bentazon application. The half-life for bentazon degradation ranges from 4.6 to 49.5 days; half-lives for some no-tillage soils with the longest histories of application are lower than those of conventional tillage soils. Half-lives for soils with no bentazon history are 3-11 times higher than the half- lives of those previously exposed to bentazon. N- Methylbentazon is the most consistently observed metabolite. The other metabolites identified in soils result from hydroxylation on the phenyl ring and the cleavage of the benzothiadiazine ring, yielding 6- and 8-hydroxybentazons and anthranilic acid via 2-amino-N-isopropylbenzamide.

storage

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Store in tightly closed containers in a cool, well-ventilated area away from flammablematerials, sources of heat and fire.

Shipping

UN2588 Pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1—Poisonous materials, Technical Name Required.

Incompatibilities

Keep away from flammable materials, heat and flame. Risk of fire and explosion if formulations contain flammable/explosive solvents.

Waste Disposal

In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers. Must be disposed properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office.