Herbicide mixtures

S. Lacorte, D. Barcelo and R. Tauler, Determination of traces of herbicide mixtures in water by... 

This technique has been used for the determination of polychlorobiphenyls, polychlorodibenzo-p-dioxins, polychlorodibenzofurans, alkyl phosphates, chlorinated insecticides, organophosphorus insecticides, triazine herbicides. Dacthal insecticide, insecticide/herbicide mixtures, mixtures of organic compounds and organotin compounds in soils, and polyaromatic compounds, polychlorobiphenyls, chlorinated insecticides and organotin compounds in non-saline sediments and anionic surfactants in sludges. 

Woodrow JE, Selber JN, Yong-Hwe K (1986) Measured and calculated evaporation losses of two petroleum hydrocarbon herbicide mixtures under laboratory and field conditions. Environ Sci Technol 20 783-786... 

Further information on the determination of herbicides is shown in Table 4.10. The analysis of insecticide/herbicide mixtures in soil has been reviewed by various workers [279,491-522]. The determination of other miscellaneous agrichemicals is shown in Table 4.11. 

Another prepackaged herbicide mixture was AAtram , the combination of Ramrod (propachlor) and atrazine, formulated as granules. AAtram was introduced in the western Com Belt and Great Plains in the early 1970s and was sold for only a few years. 

Smith, A.E. (1979) Soil persistence experiments with (14C) 2,4-D in herbicidal mixtures and field persistence studies with triallate and trifluralin both singly and combined. Weed Res. 19, 165-170. 

Herbicides comprise 60-70 percent of total usage of pesticides in developed countries. Plants develop resistance to herbicides which in turn demands altered management strategies through improved herbicides and/or herbicide mixtures. This may involve different modes of action, for short-term efficacy and long-term control to be effective. 

Table V. Effect of Desalting an ACCase-Herbicide Mixture on Enzyme Activity...

M.F. Cavieres, J. Jaeger and W. Porter, Developmental Toxicity of a Commercial Herbicide Mixture in Mice I, Effects on embryo implantation and litter size, Environmental Health Perspecitves, 2002, 110, 1081. 

Spraying vegetation during the Vietnam War with the defoliant Agent Orange, a mixture of 2,4-D and 2,4,5-T. This herbicide mixture was contaminated with dioxin. 

Herbicide resistant populations have evolved only in monoculture and/or mono-herbicide conditions at the rates we have previously predicted. Contrary to our original model, no populations of atrazine-resistant weeds have appeared in corn where rotations of crops and herbicides or herbicide mixtures were used. This is due to the previous lack of information about the greatly reduced fitness of the resistant individuals, which could be expressed only during rotational cycles, and also to the greater sensitivity of resistant individuals to other herbicides, pests and control practices. 

Phenoxyacetic acid herbicides Mixture of several phenoxyacetic acid herbicides Adsorption Perisorb A pellicular adsorbent Hexane/acetic acid (92.5 7.5)... 

Thiocarbamate herbicide mixtures containing eptam, pebulate, and cycloate thiobencarb, molinate, pebulate, and vemolate or pebulate and vemolate were separated by concomitant adsoiption and partition TLC because of the close values. Silufol UV254 plates were developed by hexane-ether (3 1) for adsorption and an acetone-water (6 4) mixture for partition TLC where the plates were impregnated with vaseline oil (91). 

From the above discussion, it is evident that in order to test the observed response of a target plant to the application of a herbicide mixture and characterize it as additive, synergistic, or antagonistic, an expected or predicted response should be well defined. The calculation of a predicted response requires the selection of an appropriate reference model. Such a selection is not difficult when only one component of a mixture is biologically active on a target plant. When both components of a herbicide mixture are biologically active, the definition and selection of a reference model is more complex. ... 

The ADM is valid for studying the interactions of herbicides with other herbicides or nonherbicides that exhibit similar action. Under the assumptions of the ADM, the growth responses of a test plant to the joint application of two components of a herbicide mixture are equated to the sum of the responses to each chemical tested separately.Thus, the predicted dose-response relationships for a herbicide mixture using the ADM are such that if one component of the mixture is replaced at a constant proportion by the other, the predicted response remains unchanged. Methods developed for the prediction of plant responses to herbicide mixtures using the ASM include the isobole method, the ANOVA method, and the two-parameter method. " ... 

The MSM is appropriate for predicting plant responses to herbicide mixtures whose components act by different modes of action. Use of the MSM requires that experimental observations be expressed as percentages or proportions of a hypothetical maximum measure of activityUnder these assumptions, the MSM equates the proportion of the observed response of a test plant to the action of a herbicide mixture to the product of the corresponding proportions observed when the two components of the mixture are administered separately. Methods developed for the prediction of plant response to herbicide mixtures using the MSM include Colby s equation, the MSM equation developed by Morse, and the regression method of Nash. " Recently, Flint et devised a method for the statistical treatment of Colby s equation. 

Chemical modifiers of the action of selected herbicides can interact with the respective herbicides either outside or inside the target or nontarget plant species. Interactions may also occur before application while herbicides are mixed with other herbicides or auxiliary chemicals in the spray tank. Chemical or physical incompatibility of herbicide mixtures has been reviewed elsewhere " and is outside the scope of this chapter. 

Adverse interactions between herbicides and other herbicides or nonherbicide chemicals on higher plants have been well documented. The continuous discovery and development of new herbicides dictates the need for continuing studies of the potential interactions of herbicide mixtures. A better understanding of herbicide interactions will facilitate the efficient use of mixtures of old and new herbicides in future crop production. 

Of the currently known interactions of herbicides with other agrochemicals on higher plants, only a few appear to result from the interference of a selected agrochemical with herbicidal activity at target sites. Examples of such interactions are the main topic of the discussion presented in this chapter. Further advances in our understanding of the mechanisms of action and metabolism of specific herbicides will facilitate our ability to predict the performance of herbicide mixtures. 

---