Publications (2)0 Total impact
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Article: The origins of selectivity and performance of a new pre‐emergence bleaching herbicide, WL 110547. Part I: Factors affecting uptake
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ABSTRACT: A novel compound, 1-(3-trifluoromethylphenyl)-5-phenoxy-1,2,3,4-tetrazole (WL 110547) is a pre-emergence bleaching herbicide with selectivities in certain crops. These selectivities and the weed-control spectrum are derived, in part, from features which influence the uptake of WL 110547 into sensitive tissue. WL 110547 is strongly adsorbed to soil with measured Kocvalues in the range 1500-2500 and, following application, is confined to the surface layers of soil, especially when the organic matter content is high. Some plant species have anatomical features which protect their developing leaf tissue from contact with the soil during emergence and thus escape direct contact with these treated layers. Furthermore, some of these plants are deeply rooted and thus there is little opportunity for sufficient uptake of WL 110547 to cause a phytotoxic effect.However some weeds, especially annual dicotyledons, germinate only from shallow depths and, during emergence, their cotyledons or leaves are in contact with the soil. In soils treated with WL 110547 they can thus absorb phytotoxic concentrations of herbicide directly into their cotyledons or leaves. Additional uptake may also occur through roots near the surface and allow WL 110547 to be translocated via the transpiration stream to the site of action in cotyledons and leaves and enhance phytotoxicity.Knowledge of the features controlling uptake, combined with a knowledge of intrinsic susceptibility, have allowed an understanding of the spectrum of weed control and the selectivities between weeds and crops.Pesticide Science 05/2006; 28(2):123 - 141. -
Article: The origins of selectivity and performance of a new pre‐emergence bleaching herbicide, WL 110547. Part II: Plant and environmental factors influencing biological activity
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ABSTRACT: Pre-emergence applications of the novel tetrazole herbicide WL 110547 control a number of economically important grass and broad-leaved weed species in small grain cereals. To assess the influence of plant and environmental factors on the biological performance of WL 110547, a series of tests were carried out under controlled conditions and, where appropriate, comparisons were made with field observations.When presented with the maximum opportunity for compound uptake in the absence of soil, differences in the degree of susceptibility to WL 110547 were observed amongst both monocotyledonous and dicotyledonous species, although the latter group generally showed higher levels of phytotoxicity. This species susceptibility to WL 110547 was unaffected by temperature.Increasing the sowing depth in soil decreased the level of effect of WL 110547 on a number of monocotyledonous species, although small-seeded species (e.g. blackgrass, annual meadow grass), emerging from deep in the soil profile, subsequently developed levels of phytotoxicity comparable to, or even greater than, shallow-planted seedlings. This was attributed to less vigorous seedlings, emerging from depth, that were unable to regenerate new tissue and grow away from a treated soil layer. Reduced growth rates of wild oat, blackgrass and speedwell, induced by low temperatures, also increased the phytotoxicity of WL 110547. Furthermore, applications of WL 110547 during seedling emergence maximised herbicide effect, as did seedling emergence through moist rather than dry soil.The results are discussed in relation to the mobility of the herbicide in soil, the mode of action of WL 110547, its availability to the plant and the duration of contact between emerging shoot and treated soil layer.Pesticide Science 05/2006; 28(2):143 - 156.
