HERBICIDE EFFECTS ON PLANT DISEASE

Abstract

To be effective, herbicides they must have strong biological activity against plants. Indirectly through their effects on plants, herbicides can influence almost any process or interaction of the plant, including its susceptibility to plant diseases. In some cases, herbicides also have direct effects on plant pathogens. In this short review, we will discuss both types of effect, and, where possible, provide the mechanism for the effect. We provide a separate section for glyphosate because of the relatively large amount of information on the effects of this very important herbicide on plant diseases and the fact that there have been many seemingly conflicting claims of the effect of glyphosate on diseases in glyphosate-resistant crops (Duke & Cerdeira, 2005). The topic of herbicide effects on plant diseases has been reviewed previously, either as a single topic (e.g., Altman, 1991; Altman & Campbell, 1979; Katan & Eshel, 1973; Levesque et al., 1992) or as part of a more extensive review on secondary effects of pesticides (several of these are in the book by Altman, 1993) or chemical effects on microbial weed biocontrol agents (Hoagland, 1996). There have been no recent reviews of this topic, but a large amount of information has not been generated since the last review of this topic, except in the case of glyphosate.