Herbicide Effects on Plant Disease

Authors: Duke, Stephen; Wedge, David; CERDEIRA, ANTONIO - BRAZIL. DEPT. OF AG.; MATALLO, MARCUS - INST. BIOLOGICO-BRAZIL

Submitted to: Pest Management Science
Publication Type: Review Article
Publication Acceptance Date: 1/20/2007
Publication Date: 2/13/2007
Citation: Duke, S.O., Wedge, D.E., Cerdeira, A.L., Matallo, M.B. 2007. Herbicide Effects on Plant Disease. Pest Management Science. 18:36-40.

Interpretive Summary: The effect of herbicides on plant disease is an important, but generally overlooked, aspect of integrated pest management. Furthermore, these interactions can be crucial contributors to the success or failure of the biocontrol of weeds with microbes. Indirectly, through their strong 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 effects, and, where possible, provide the mechanism for the effect. 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 & Rahe, 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. Much of the older literature was descriptive, without much attempt to determine the mechanism of the interactions. This topic is complicated by the complex interactions of herbicide dose, formulation, tillage systems, environmental conditions, the plant pathogen, and the plant. Furthermore, the timing of infection with the pathogen vs. that of the herbicide treatment can have a profound influence on the interaction. Thus, the literature often appears to be conflicting, but the apparent conflicts may be due to differences in one or more of the factors involved.

Technical Abstract: The effect of herbicides on plant disease is an important, but generally overlooked, aspect of integrated pest management. Furthermore, these interactions can be crucial contributors to the success or failure of the biocontrol of weeds with microbes. Indirectly, through their strong 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 effects, and, where possible, provide the mechanism for the effect. 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 & Rahe, 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. Much of the older literature was descriptive, without much attempt to determine the mechanism of the interactions. This topic is complicated by the complex interactions of herbicide dose, formulation, tillage systems, environmental conditions, the plant pathogen, and the plant. Furthermore, the timing of infection with the pathogen vs. that of the herbicide treatment can have a profound influence on the interaction. Thus, the literature often appears to be conflicting, but the apparent conflicts may be due to differences in one or more of the factors involved.