Dicamba
- 3,6- dichloro-2- methoxybenzoic acid
- 3,6-dichloro -o- anisic acid
White solid with kresolartigem odor
Fixed
1.49 g · cm -3
116 ° C.
> 200 ° C
4.5 MPa (25 ° C)
Poorly in water ( 6500 mg · l-1 at 20 ° C)
Risk
Template: Infobox chemical / molecular formula search available
Dicamba or 3,6- dichloro-2- methoxybenzoic acid is a synthetic auxin, and is used as a herbicide. 1965, it was brought by the Velsicol Chemical Corporation for the first time on the market. Dicamba is under the name Banvel, Banex, Dianat, Fallowmaster, Mediben, Metambane, Tracker, Trooper and Velsicol commercially.
- 3.1 Properties
- 3.2 Acute Toxicity
- 3.3 Chronic Toxicity
- 3.4 Other
- 4.1 degradability 4.1.1 soil
- 4.1.2 water
- 4.1.3 vegetation
Use
Plant protection
Dicamba is used as a herbicide against Dicotyledons in cereals, orchards, grassland and grass. Many of today's approved dicamba products are intended for use against weeds on lawns, Nutzrasen and green stripes on roads. They contain, among other herbicidal active compounds often 2,4-dichlorophenoxyacetic acid. Plant protection products containing the active ingredient dicamba are allowed in Germany, Austria and Switzerland.
Effect
Dicamba is absorbed through leaves and roots, it can be transported within the plant. Dicamba is a so-called auxin herbicide, which so greatly accelerated the growth of dicotyledonous plants that they received due to the resulting nutrient deficiency. Warm and growth-promoting weather accelerates the Absterbeprozess. Until the herbicidal activity occurs, plants need several days active growth.
Chemistry
Properties
The colorless crystals decompose when heated, forming corrosive, toxic fumes ( hydrogen chloride). Dicamba is soluble in acetone, dichloromethane, 1,4-dioxane, ethanol, toluene, and xylene.
Acute toxicity
The LD50 (oral ) for the male rat is 1581 mg, for the female rats at 1879 mg dicamba / kg body weight. In male mice it is 1180, in female 2392 mg / kg.
In dermal LD50 is for the male rat is> 6000, for the female rat is> 8000 and for the rabbits > 2000 mg / kg body weight. In the rabbit, dicamba does not irritate the skin, but irritates the eye very strong. In guinea pig skin sensitization was observed.
The following symptoms characterize a dicamba - intoxication: anorexia, vomiting, muscle weakness, bradycardia, dyspnea, CNS symptoms, benzoic acid in the urine, urinary or fecal incontinence, cyanosis
In addition, dicamba irritates the mucous membranes and eyes, a temporary clouding of the cornea is the result of direct contact with eyes. Most people with massive dicamba poisoning recovered within 2-3 days without permanent damage.
Chronic Toxicity
Doses of 25 mg / kg / day over a period of 2 years in rats caused no measurable effects regarding death rate, body weight, food consumption, body weight, blood chemistry or tissue structure. High doses of dicamba caused changes in liver tissue and a decrease in body weight in rats and mice.
Others
An absorption through the skin is almost not take place. In a study of three generations of rats dicamba had no measurable effect on the rate of reproduction in use concentration. Teratogenic, carcinogenic and mutagenic effects were not observed.
Ecology
Degradability
Ground
Dicamba is moderately persistent in soil. The half-life of 1-4 weeks. Under optimum conditions (soil moisture < 50 %, slightly acidic pH ), the metabolization by microorganisms within 2 weeks, photolysis plays only a minor role. Due to its water solubility and its very low tendency toward adsorption to soil particles, contamination of groundwater by washing out is possible.
Water
Since dicamba is stable in water, the reduction to 95% is done by micro-organisms and to 5% by photolysis.
Vegetation
The differences in the rate of degradation of dicamba to 3,6-dichloro- 1-hydroxy- benzoic acid in different plant species are the cause of its selective action. In addition, hydroxylation is at the 5- position of the ring of significance can be formed on the polar conjugates.
Ecotoxicity
Dicamba is not toxic to bees.
The acute lethal dose (LD50 ) for the mallard duck is 2000 mg / kg body weight. In 8- day feeding test with mallard ducks and quail Japan, the lethal concentration was> 10,000 mg / kg feed.
The LC50 of dicamba is in rainbow trout ( 96 h) 135 mg / L and carp (48 h ) 465 mg / L. Thus, it is considered not toxic to fish. The EC50 ( 48 h) for Daphnia magna and the LC50 ( 96 h ) for the amphipod be more than 100 mg / L.
Dicamba is toxic to algae and higher aquatic plants.
Dicamba - resistant crops
The University of Nebraska and Monsanto have developed using genetic engineering methods soybeans that are resistant to dicamba. In January 2009, Monsanto and BASF - agreed to cooperate on the development of new herbicide-resistant plants - the main producers of dicamba and dicambahaltigen products. In light of the spread of weeds that are resistant to glyphosate (Roundup ), both groups want to develop seeds that are resistant to both glyphosate and dicamba against.