− | Agricultural weeds cause an overall reduction in yield. Most weed species are accidental introductions with crop seeds and imported plant material. Many introduced weeds in pastures compete with native forage plants, are toxic (e.g., leafy spurge, ''[[Euphorbia esula]]'') to cattle or non palatable due to thorns and spines (e.g., yellow star thistle, ''[[Centaurea solstitialis]]''). Forage loss due to invasive weeds on pastures amounts to nearly $1 billion in the U.S. alone (Pimentel ''et al.'' 2005). A decline in pollinator services and loss of fruit production has been observed due to the infection of honey bees (''[[Western honeybee|Apis mellifera]]'' another invasive species to the Americas) by the invasive [[varroa mite]]. Introduced rodents (rats, ''Rattus rattus'' and ''R. norvegicus'') have become serious pests on farms destroying stored | + | Agricultural weeds cause an overall reduction in yield. Most weed species are accidental introductions with crop seeds and imported plant material. Many introduced weeds in pastures compete with native forage plants, are toxic (e.g., leafy spurge, ''[[Euphorbia esula]]'') to cattle or non palatable due to thorns and spines (e.g., yellow star thistle, ''[[Centaurea solstitialis]]''). Forage loss due to invasive weeds on pastures amounts to nearly $1 billion in the U.S. alone (Pimentel ''et al.'' 2005). A decline in pollinator services and loss of fruit production has been observed due to the infection of honey bees (''[[Western honeybee|Apis mellifera]]'' another invasive species to the Americas) by the invasive [[varroa mite]]. Introduced rodents (rats, ''Rattus rattus'' and ''R. norvegicus'') have become serious pests on farms destroying stored grains (Pimentel ''et al.'' 2005). |