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Joint action of root‐absorbed mixtures of auxin herbicides in Sinapis alba L. and barley ( Hordeum vulgare L.)
Author(s) -
STREIBIG J. C.
Publication year - 1987
Publication title -
weed research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 74
eISSN - 1365-3180
pISSN - 0043-1737
DOI - 10.1111/j.1365-3180.1987.tb00771.x
Subject(s) - dicamba , mcpa , hordeum vulgare , chemistry , phytotoxicity , mode of action , bromus tectorum , sinapis , botany , poaceae , agronomy , biology , pesticide , weed control , biochemistry , brassica , invasive species
Summary The efficacy of some binary mixtures of MCPA, 2,4‐D dichlorprop, mecoprop and dicamba was evaluated in water culture experiments. Within each of seven assays, two dose‐response curves described the phytotoxicity of the herbicides administered separately and three curves described the phytotoxicity of mixtures in fixed ratios. A non‐linear regression model of dry matter on the logarithm of the dose, assuming the five response curves to be mutually parallel, was fitted and a reference model, the Additive Dose Model (ADM) to assess the efficacy of the mixtures, was also incorporated into the regression. The biological interpretation of ADM is often associated with mixtures of compounds having similar mode of action. Mixtures of dicamba with dichlorprop or 2,4‐D were more potent than expected under ADM in two Sinapis alba assays. In one assay with mixtures of MCPA and dichlorprop the parallel‐line model fitted somewhat better than did the ADM regression. This also applied to a barley assay with mixtures of dicamba and MCPA. On the basis of the results obtained it is suggested that the analogy between the implicit assumptions of the parallel‐line assay can be extended to the ADM. Parallel dose response curves are a necessary but not a sufficient condition for assuming similar mode of action Similarly, it can be argued that mixtures of compounds following ADM are a necessary but not a sufficient condition for assuming a similar mode of action for the herbicides in a mixture.