Genetic variability of invasive plant populations may create significant challenges to weed management through (1) selection for resistant genotypes and (2) differential efficacy of control methods resulting from genotypic variation. Effects of variation on management success may be particularly problematic for native invasive plants because they possess more genetic variation than bottlenecked exotic invasive species. We review the influence of genetic variation among populations and species on efficacy of chemical and biological control of select invasive rangeland plants. Population or genotype variation was more important for successful management when using biological agents than when using herbicides. Long-term success in weed control requires integrating multiple management strategies with attention to specificity of biological control agents to avoid selection for resistant genotypes.
Additional index words: Biological control, common garden, genetic variation, metsulfuron, native plants, picloram, rangeland plants.