Mechanisms of Herbicide Safener Action

When applied alone, safeners generally have Utde visible effects on crop or weed species. This was found, for example, for the safeners fenchlorazole-ethyl and mefenpyr-diethyl [20, 21]. In contrast, fenchlorazole-ethyl exerted an immediate protective effect on wheat and prevented even a transient inhibition of leaf growth by fenoxaprop-ethyl [22). The same was observed subsequently for combinations of mefenpyr-diethyl with fenoxaprop-P-ethyl. 

Potentially, a safener could increase the tolerance of the crop by reduction of herbicide uptake and translocation, or by enhancement of metabolic herbicide inactivation in the crop tissue. Furthermore, a safener could counteract the effect of a herbicide at its biochemical target site, with a resultant reduction of crop susceptibility. Evidence for and against these potential modes of action is presented in the following sub-sections. In addition, aspects of safener specificity (crop versus weed) are covered for situations where the safener is applied in tank mix with the herbicide. 

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