Definitions

Below are definitions frequently used in discussions of weed resistance management. Below each phrase is a link you can visit for more information.


Cross Resistance: Cross resistance exists when a weed population is resistant to two or more herbicides. The presence of cross resistance can complicate the selection of alternate herbicides as tools to control herbicide-resistant weeds.
Source: Herbicide Resistance Action Committee (http://www.plantprotection.org/hrac/Guideline.html#definitions


Herbicide Mode of Action: Herbicide mode of action refers to the biochemical mechanism by which a herbicide causes growth to cease in target weeds. Herbicides can be classified into groups according to their modes of action.
Source: Herbicide Resistance Action Committee (http://www.plantprotection.org/hrac/Guideline.html#definitions


Herbicide Resistance: Herbicide resistance is the inherited ability of a plant to survive and reproduce following exposure to a dose of herbicide normally lethal to the wild type. In a plant, resistance may be naturally occurring or induced by such techniques as genetic engineering or selection of variants produced by tissue culture or mutagenesis.
Source: Weed Science Society of America; International Survey of Herbicide Resistant Weeds (http://www.weedscience.org/paper/definitions.htm)


Herbicide Tolerance: Herbicide tolerance is the inherent ability of a species to survive and reproduce after herbicide treatment. This implies that there was no selection or genetic manipulation to make the plant tolerant; it is naturally tolerant.
Source: Weed Science Society of America; International Survey of Herbicide Resistant Weeds (http://www.weedscience.org/paper/definitions.htm)


Resistance Mechanism: Resistance mechanism refers to the method by which a resistant plant overcomes the effect of a herbicide.
Source: Herbicide Resistance Action Committee (http://www.plantprotection.org/hrac/Guideline.html#definitions


Selection Intensity: Selection intensity is the degree to which weed control measures, for example, herbicides in a cropping system, give a competitive advantage to a weed biotype.
Source: http://www.extension.umn.edu/distribution/cropsystems/DC6077.html
#Definitions


Weed Resistance: Resistance is the naturally occurring inheritable ability of some weed biotypes within a given weed population to survive a herbicide treatment that would, under normal use conditions, effectively control that weed population. Selection of resistant biotypes may result in control failures.
Source: Herbicide Resistance Action Committee (http://www.plantprotection.org/hrac/Guideline.html#definitions