Herbicide selective

C2H4N4. A translocated herbicide, m.p. 157-159 C, used as a non-selective herbicide on fallow land or in established orchards. 

CgHjClaOj. M.p. 155°C. Used as a selective herbicide. It is made from 2,4,5-trichloro-pheno) and sodium chloroacetate. Ester sprays and combined ester sprays with 2,4-D are available. 2,4,5-T products are of particular value in that they control many woody species, and eradicate perennial weeds such as nettles in pastures. 

H Br Effective non 776 selective herbicide in controlling weeds in orchards and forests ... 

The amine group of 3-arninoben2otrifluoride can be replaced by Cl, Br, I, F, CN, or OH groups by standard dia2oti2ation reactions. Phosgenation gives 3-trifluoromethylphenyhsocyanate [329-01-1/, which can then be converted to the selective herbicide fluometuron [2164-17-2] a substituted urea. Application. 

Herbicide Glasses and Databases. Herbicides can be classified as selective and nonselective. Selective herbicides, like 2,4-D (2,4-dichlorophenoxyacetic acid), metolachlor [51218-45-2] and EPTC [759-94 ] are more effective against some types of plants than others, eg, broadleaved plants vs grasses. Glyphosate [1071 -83-6] is representative of the nonselective herbicides used for total vegetable control. 

Although the ratios have varied from year to year since 1979, the selective herbicides used in com production have accounted for approximately 21% of herbicide use on a per crop basis (24). Herbicide use in soybean and cotton production combined account for ca 23% of the selective herbicide market. Graminicides, which selectively kill grasses, constitute 40% of the total market, leaving a market share of approximately 16% for the nonselective herbicides. 

Important chemicals derived from phenol are salicylic acid acetylsali-cyclic acid (aspirin) 2,4-dichlorophenoxy acetic acid (2,4-D), and 2,4,5-triphenoxy acetic acid (2,4,5-T), which are selective herbicides and pentachlorophenol, a wood preservative ... 

The pyrrolotriazines 32 were prepared from 3,4-dihydro-5-ethoxy-2//-pyrrole 31 by sequential reaction with hydrazine hydrate and a-oxoesters (85GEP3340026). They are useful as selective herbicides (Scheme 10). 

Inhibitors must possess chemical and physical properties that will ensure absorption by root tips or penetration by foliar surfaces, and translocation to the active site. Once there they must assume the precise spatial configuration required to complement the molecular architecture of the active center if they are to block the key reaction. A comprehension of comparative biochemistry and information on how plants differ in the architecture of the reactive sites should assist in developing truly selective herbicides. 

In general, triazines are pre- and post-emergence selective herbicides particularly effective on annual and perennial broadleaf and grassy weeds in corn, sorghum, cotton, soybeans, sugar cane, and a host of other fruit and cereal crops. Some have anti-fungicidal properties (e.g., anilazine), and some (e.g., simazine) can be used for... 

Atrazine, used as a selective pre- and post-emergence herbicide to control annual weeds in several crops, is the most representative compound of this group. It is also used as a non-selective herbicide in non-crop areas. After absorption, the compound is metabolized to dealkylated and deisopropy-lated derivatives. The unchanged compound and its metabolites are excreted in urine, where they can be detected by chromatography or enzyme-linked immunosorbent assay (Lucas et al., 1993). A mercapturic acid conjugate of atrazine has also been found in urine samples of workers spraying this herbicide (Lucas et al., 1993) (Table 6). 

Similarly, the selective herbicides, bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) and ioxynil (3,5-diiodo-4-hydroxybenzonitrile) are degraded by soil bacteria to their corresponding amide products 3,5-dibromo-4-hydroxybenzamide (BrAM) and 3,5-diiodo-4-hydroxybenzamide (IAM) but are not further degraded to the corresponding acids. The identification of amidases or nitrilases able to effect these transformations, in a soil bacterium, would be of value as a bioremediation agent [48],... 

Atrazine is a white crystalline substance that is sold under a variety of trade names for use primarily as a selective herbicide to control broadleaf and grassy weeds in com and sorghum... 

Selective control, 20 697-698 Selective flocculation, 8 711 Selective herbicides, 13 284-285, 313, 363 Selective leaching... 

Substituted dinitroanilines (Fig. 10, Table 3) are an important series of selective herbicides commercially introduced in agriculture in the 1960s. Trifluralin is the most prominent member of this series. Nitralin and Benfluralin have also received widespread usage, while Profluralin is a relatively recent herbicide of this class. Dinitro anilines show very low water solubilities. Nitralin and Benfluralin have low vapor pressures and are nonvolatile, while Trifluralin is relatively volatile. All these compounds have been shown to be relatively immobile in soil systems. 

Following considerations based on usage information, physico-chemical properties, and persistence, a priority list of herbicides was established for the Mediterranean countries, i.e., France, Italy, Greece, and Spain ([168, 182, 183] Table 6). This list considers selected herbicides which can cause contamination of estuarine and coastal environments. The selection of pollutants has been based on the availability of usage data and the consideration of half-lives [182,183]. 

Mersch-Sundermann V, HofmeisterA, Mueller G, etal. 1989. [Examination of mutagenicity of organic microcontaminations of the environment. III. Communication The mutagenicity of selected herbicides and insecticides with the SOS-chromotest]. ZbI Hyg 189 135-146. (German). 

Uses Dormant ovicidal spray for fruit trees (highly phototoxic and cannot be used successfully on actively growing plants) selective herbicide and insecticide. 

MacRae, I.C. and Alexander, M. Microbial degradation of selected herbicides in soil, 7 Agric. Food Chem., 13(1) 72-75,1965. 

Paschke, A., Neitzel, P.E., Walther, W., and Schiirmann, G. Octanol/water partition coefficient of selected herbicides determination using shake-flask method and reversed-phase high-performance liquid chromatography, J. Chem. Eng. Data, 49(6) 1639-1642, 2004. 

Mitchell G Bartlett DW, Fraser TEM, Hawkes TR, Holt DC, Townson JK, Wichert RA. (2001) Mesotrione Anew selective herbicide for use in maize. Pest Manag Sci 57 120-128. 

The product is a broad-spectrum, non-selective herbicide particularly effective against perennial weeds such as nutsedge and bindweed. Since the effect of changes in structure on biological activity is similar in several series of compounds, this topic will be discussed later. 

Although the compounds described above were non-selective herbicides and aromatic substitution resulted in compounds of lower activity, it was gratifying to find that the mixture, coded AC 222,293, and prepared as shown in Scheme I, had good activity against wild oats, black grass and mustards yet was well tolerated by most winter and spring wheats and barleys. 

Herbicide evaluation of the product from this sequence of reactions showed that it was a very active but non-selective herbicide. We were unable to determine with certainty at this point the regiochemistry of the product. 

Herbicides. The idea of using allelopathy in weed control was conceived in the late seventies (121. and several workers have considered this possibility, as already mentioned (13-161. However, characterization and possible use of allelochemicals as selective herbicides received attention only recently, and our demonstrations of the selective herbicidal activity of caffeine are among the pioneer ones (17-211. 

---