Herbicides picloram

The 198th ACS meeting certainly is a landmark meeting in the immunoassay field. For the first time at this meeting we have seen reports from a variety of major agricultural chemical companies about the in-house efforts in immunodiagnostics (11-24-29) as well as collaborative validation studies between a biotechnology company and a university (30) and a contract laboratory (31). In addition to the development of polyclonal based systems, there is an increased interest in the development of monoclonal antibodies for environmental chemicals (12,11,32). Deschamps and Hall (32) presented a nice comparison of the relative attributes of mono- vs polyclonal based systems for the herbicide picloram. 

The largest use of a-picoline (2) is for production of 2-vinylpyridine (11) which, with butadiene and styrene, is converted into a terpolymer latex. This latex provides a coating that stiffens fabrics (e. g. nylon, polyester, rayon) that are incorporated into biased-ply car tires. The 2-vinylpyridinc assists in binding the rubber to the fabric carcass. a-Picoline is also used as a precursor to nitrapyrin (12), which prevents nitrogen loss from soil, and the herbicide picloram (13). 

Tout NL, Yau K Y, Trevors J T, et al. (2001). Synthesis of ligand-specific phage-display ScFv against the herbicide picloram by direct cloning from hyperimmunized mouse. J. Agric. Food Chem. 49 3628-3637. 

Arvik et al. (1971), working with the herbicide picloram (which produces effects in higher plants similar to that of auxin-type synthetic growth regulators), found that it had no influence on the algae of a clay loam soil. These workers treated plots with this herbicide at 0.28, 0.56, and 1.12 kg/ha. Samples were collected from three soil levels, three, six, and 18 mon after treatment. None of the 16 species observed was qualitatively or quantitatively affected by the herbicide treatments. 

In a brush application instead of an aquatic one, the results were found to be different. 2,4-D (2,4-dichloro-phenoxyacetic acid), 2,4,5-T (2,4,5-trichlorophenoxyacetic acid), dicamba (3,6-dichloro-q-anisic acid), and picloram (4-amino-3,5,6-trichloropicolinic acid) were prepared in this same way and applied to brush control alone and in combinations. Generally there was no difference in effectiveness between conventional and polymerized herbicides. Picloram, however, was more effective when applied conventionally. ... 

Other auxin-like herbicides (2,48) include the chlorobenzoic acids, eg, dicamba and chloramben, and miscellaneous compounds such as picloram, a substituted picolinic acid, and naptalam (see Table 1). Naptalam is not halogenated and is reported to function as an antiauxin, competitively blocking lAA action (199). TIBA is an antiauxin used in receptor site and other plant growth studies at the molecular level (201). Diclofop-methyl and diclofop are also potent, rapid inhibitors of auxin-stimulated response in monocots (93,94). Diclofop is reported to act as a proton ionophore, dissipating cell membrane potential and perturbing membrane functions. 

The primary use of a-picoline (2) is as a precursor of 2-vinylpyridine (23). It is also used in a variety of agrochemicals and pharmaceuticals, such as nitrapyrin [1929-82-4] (60) to prevent loss of ammonia from fertilizers picloram [1918-02-1] (61), a herbicide and amproHum [121 -25-5] (62), a coccidiostat. 

The recovery of vegetation in a tropical rainforest in Puerto Rico — after plants were deliberately subjected to lethal doses of gamma radiation — closely resembled secondary succession after other types of disturbances, such as mechanical stripping and treatment with the Picloram herbicide (Jordan 1969). 

Abbott et al. [163] described a pyrolysis unit for the determination of Picloram and other herbicides in soil. The determination is effected by electron capture-gas chromatography following thermal decarboxylation of the herbicide. Hall et al. [164] reported further on this method. The decarboxylation products are analysed on a column (5mm i.d.) the first 15cm of which is packed with Vycor chips (2-4mm), the next 1.05m with 3% of SE-30 on Chromosorb W (60-80 mesh) and then 0.6m with 10% of DC-200 on Gas Chrom Q (60-80 mesh). The pyrolysis tube, which is packed with Vycor chips, is maintained at 385°C. The column is operated at 165°C with nitrogen as carrier gas (110ml min-1). The method when applied to ethyl ether extracts of soil gives recoveries of 90 5%. Dennis et al. [165] have reported on the accumulation and persistence of Picloram in bottom deposits. 

Acid herbicides such as 2,4 dichlorophenoxy acetic acid, 2,4,5-trichlorophenoxy acetic acid, 3,6-dichloropicolinic acid and other types of herbicides such as Dicamba, Dichloroprop, Picloram, Fenoprop, 2,3,6-TBA, Bromoxynil and Ioxynil are widely used in agriculture and are often formulated as mixtures. They may also be mixed in the spray tank or used in sequence, so it is likely that residues of more than one of these compounds may be present in the soil. 

With the exception of picloram and phenols (Fig. 10, Table 3), acidic pesticides are considered nonvolatile from aqueous and soil systems [153]. Some ester formulations of these compounds also behave as herbicides. They do not ionize in solution and are less water-soluble than the acid or salt forms. They are eventually hydrolyzed to acid anions in aqueous and soil systems, but in the ester form are non-ionic and relatively volatile. 

Altom, J.D. and Stritzke, J.F. Degradation of dicamba, picloram, and four phenoxy herbicides in soils, WeedSci., 21 556-560, 1973. 

Treatments consist of injecting herbicide through the bark and into the vascular system of target trees. The most commonly used herbicides are 2,4-D, and Tordon 101 (2,4-D + picloram). The total list of registered products is shown in Table VI. 

Many chemicals are regulated by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and their properties are as diverse as the properties of ecosystems. In forestry, however, relatively few herbicides are used very much. In fiscal year 1981, for instance, the USDA Forest Service used more than 25 different herbicides in the National Forests, but 2,4-D and picloram alone and in combination accounted for 70% of the total amount of herbicide applied. Atrazine, glyphosate, dalapon, simazine, fosamine, and hexazinone accounted for an additional 18% (2). 

Lee et al. [187] developed a multi-residue method with a low detection limit for 10 commonly used acid herbicides in non saline waters. The herbicides were Dicamba, MCPA, 2,4-DP, 2,3,6-TBA, 2,4-D, Silvex, 2,4,5-T, MCPB, 2,4,5-DB and Picloram. The method used solvent extraction and the formation of pentafluorobenzyl esters. The derivatives were quantified by capillary column gas chromatography with electron capture detection. The detection limit was 0.05pg L. Recoveries of herbicides from spiked Ontario lake water (0.5-1.Opg L 1) were 73-108% except for Picloram recovery which was 59% at 0.1 pg L 1. 

The nine herbicides studied by these workers were Dicamba, MCPA, MCPB, 2,4-DB, Picloram (4-amino-3,5,6-trichloropicolinic acid), 2,4-D, 2,4,5-T, Silvex and 2,4-DP. 

Abbott et al. [196] described a pyrolysis unit for the determination of Picloram and other herbicides in water. The determination is effected by electron capture-gas chromatography following thermal decarboxylation of the herbicide. Hall et al. [197] reported further on this method. 

Uses Picloram belongs to the pyridine family of compounds. It is a systemic herbicide used for the control of woody plants and a range of broadleaf weeds. Most grasses are resistant to picloram. It is classified by the USEPA as RUP because of its mobility in water, combined with extreme sensitivity to many important crop plants.2,12,13,37... 

Urea, triazine, and picloram—they represent a class of herbicides and exhibit a soil persistence in the range of 1-2 yr... 

In this context, we recently discovered close correlations between auxin-induced ethylene synthesis, massive accumulations of ABA in root md even more in shoot tissue and inhibition of their growth. This phenomenon, which has been reported for the first time, was demonstrated for auxin herbicides from different chemical classes (Figure 1), such as quinmerac, quinclorac, MCPA, naphthalene acetic acid, dicamba and picloram, and lAA at high concentration, in a variety of dicot species, including members of the Sola-naceae, Umbelliferae, Fabaceae, Scrophulariaceae and Brassicaceae [35, 39, 40]. ABA accumulation and concomitant epinastic effects and reduced shoot growth were also... 

This group of herbicides consists of clopyralid, fluroxypr, picloram, and triclopyr. These compounds have both soil absorption and foliar activity. 

Picloram and its salts are systemic herbicides produced by chlorination of 2-methylpyridine followed by hydrolysis and reaction with ammonia. Most broadleaf crops, except crucifers, are sensitive most grasses are resistant. Picloram is effective in controlling annual weeds, is used alone or in combination with 2,4-D against deep-rooted perennials on noncropland, and is used typically as pellets or in combination with 2,4-D or 2,4,5-T for brush control. 

Picloram is either a colorless powder or crystalline solid having very low vapor pressure, making inhalation exposure unlikely unless the dust is inhaled. Exposure to picloram occurs mainly through its manufacture and its use as a herbicide in forests. Environmental exposures in humans occur when forest visitors or others not directly involved in spray operations come in contact with spray or sprayed foliage, inhale spray mist, eat plants or animals contaminated with the herbicide, or drink water containing the herbicide. A suggested no-adverse-effect level is 1.05 mg 1. ... 

Researchers at FMC Corporation have synthesized 3-(4,6-substituted benzoheterocy-clyl)uracil herbicides. The uracil ring synthesis is based on conversion of aryl amines into isocyanates68. A useful fluorinated aniline herbicide is fluometuron. Chlorination of 2-methylpyridine (102), followed by animation at the 4-position, and hydrolysis, yields the hormone-weedkiller Picloram (103) (Scheme 22). 

Three structurally related pyridine herbicides, clopyralid, fluroxypyr, and triclopyr (Figure 1) were tested for cross-reactivity with the polyclonal and monoclonal anti-picloram antibodies. 

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