Invasive exotic plants are those plants transported outside their normal home ranges and cause damage or harm in their new location. In their new homes, these alien species are free from the natural competition, herbivores, insects and diseases that normally keep populations in check. Therefore, many exotic species can spread rampantly, displace natural plant species and become nuisances. Invasive species are recognized as one of the leading threats to biodiversity and may impose enormous costs on forest managers.