Herbicide application methods

Registrations have been granted for several new herbicides that are being introduced into sugarcane their use is still relatively small. These are briefly described as to application method, rate, and weed spectrum. 

Baker, J.L. and L.E. Shiers (1989). Effects of herbicide formulation and application method on washoff from corn residue. Trans. Am. Soc. Agr. Eng., 32 830-833. 

The concept of controlling herbaceous weeds in pine plantations is relatively new. In most cases it is not necessary in order to establish a pine stand although early growth studies recently indicate that weed control can be very beneficial. As a result, herbicide technology for this purpose is just beginning to develop. More effective herbicides and application methods are currently being assessed through various university and industrial research efforts. 

Improved crop varieties and protection methods have demanded the application of many herbicides and fungicides to attain increased crop yields, decreased food costs, and enhanced appearance of food. Without proper controls, however, the residues of some pesticides on foods can create potential health risks. Proper application of herbicides and fungicides (as discussed previously) has not only lead to increased crop yield but also has reduced the hazards of persistent pesticides, such as organochlorine insecticides. However, further studies are needed to arrive at meaningful conclusions before establishing a safety in toto to biological systems and the environment. 

Sabik and Jeannot recently published an exhaustive review on SPE and multiresidue methods for the monitoring of priority herbicides in water. The same year, Thurman and Snavely proposed some views and advances related to disk extraction methods for environmental applications, including herbicides. ... 

The First Study. Forest-applicator exposure to MSMA and cacofirst studied by Tarrant and Allard (9). They collected individual urine samples on Monday mornings ari7 Friday afternoons for 9 consecutive weeks from five applicators (each using a different combination of application method and chemical) and one control. Workers were supplied with clean clothes daily, including two pair of cotton gloves (to be changed at noon, or earlier if one pair became substantially contaminated with herbicide). Complete data were obtained for weeks 2, 3, 4, 7, and 8 (except for the injection hatchet-cacodylic acid combination, which was not included in the analysis). 

Protox-inhibiting herbicides continue to be an area of interest to agrochemical companies, with most effort focused on fine tuning the 5 position of the aromatic ring of N-phenyl uracil to gain both a particular crop/weed/application method as well as a proprietary position. 

The soil analysis is presented in Table II. Small amounts of 2,4-D and 2,4,5-T were detected in soil samples receiving these herbicides. Background values from the control soils were subtracted from the observed values in treated soils. The samples were not corrected for recovery since it was better than 80% for the method. Residues decreased with time after application. Leaching and microbial decomposition could account for this observation. 

The rationale of validation experiments with fatty matrices is the high amount of fat extracted with many organic solvents. If analytes are not fat soluble and extraction is performed with water or aqueous buffer solutions, the troublesome fat is not extracted together with the analyte. Such extractions are typical for, e.g., the class of sulfonylurea herbicides. Examples exist where in such cases the applicability of an analytical method to fatty matrices was accepted by the authority without particular validation. 

This method may also be applicable to acylanilides herbicides. 

J. Strahan, Development and application of an enzyme-linked immunosorbent assay method for the determination of multiple sulfonylurea herbicides on the same microwell plate, in Environmental Immunochemical Methods, ed. J.M. Van Emon, C.L. Gerlach, and J.C. Johnson, American Chemical Society, Washington, DC, pp. 65-73 (1996). 

One application using MAE is a method to determine imidazolinone herbicides and their respective metabolites in plant tissue." Current residue methodologies for determining imazethapyr (imidazolinone herbicide) and its metabolites in crops involve laborious, time-consuming cleanup procedures after an aqueous/organic extraction. 

The toxicity and the physiological action of insecticides, fungicides, rodenticides, and herbicides on plants are of basic importance. The toxicity of treated plants to animals, and the toxicity of treated plants and animals to humans and to wildlife are of practical concern. A long-range consideration of the effect of sprays on both plant and human nutrition and its relation to public health is of direct concern. The hazards in field application and methods of protecting operators should be reported in detail and further research should be emphasized. 

Although the effect of nutrients and classical toxicants (e.g. heavy metals, herbicides) is well known, that of the so-called non-PS in biofilms is still largely unknown. Furthermore, the combination of effects, which operate at the basin scale, requires complex approaches. Therefore, the response of biofilms to these situations should trigger the development of new applications and higher standardisation in the use of biofilms. The standardisation of methods and procedures is a challenge for the future research on the use of natural and laboratory biofilms. 

Despite the advances made in high-performance liquid chromatography in recent years, there are still occasionally applications in which conventional column chromatography is employed. These methods lack the sensitivity, resolution and automation of HPLC. They include the determination of urea herbicides in soil, polyaromatic hydrocarbons, carbohydrates, chloroaliphatic compounds and humic and fulvic acids in non-saline sediments. The technique has also been applied in sludge analysis, e.g. aliphatic hydrocarbons and carboxylic acids. 

Electrophoretic and isotachoelectrophoretic techniques are gaining in popularity in soil analysis with applications to polyaromatic hydrocarbons, polychlorobiphenyls, tetrahydrothiophene and triazine herbicides, Paraquat and Diquat and growth regulators. Other lesser-used techniques include spectrophotometric methods (five determinants), spectrofluorimetric methods (two determinants), luminescence methods (one determinant), titration methods (one determinant), thin-layer chromatography (five applications), NHR spectroscopy (two applications) and enzymic immunoassays (one determinant). 

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