![](../../_themes/biocontrol/bullet2.gif) | Weeds play an important part in nutrient cycling as they tap
nutrients from the lower soil depths and return them to the
soil surface as litter. |
![](../../_themes/biocontrol/bullet2.gif) | Weeds add organic matter to the soil. |
![](../../_themes/biocontrol/bullet2.gif) | Some weeds are used as food (e.g. herbs) |
![](../../_themes/biocontrol/bullet2.gif) | Weeds prevent or reduce wind and water erosion of the land. |
![](../../_themes/biocontrol/bullet2.gif) | Weeds may be the source of drugs used in tropical public
health to cure headaches, skin diseases and syphilis. |
![](../../_themes/biocontrol/bullet2.gif) | Weeds have been the source of some natural pesticides (e.g.
pyrethrum from chrysanthemum). |
![](../../_themes/biocontrol/bullet2.gif) | Weeds act as a source of genetic materials for crop
improvement (e.g. breeding for insect pest and plant disease
resistance). |
![](../../_themes/biocontrol/bullet2.gif) | Weeds may beautify the landscape. Some house and garden
plants have come straight from the wild state (e.g.
Bryophyllum spp.). |
![](../../_themes/biocontrol/bullet2.gif) | Weed eradication projects may provide employment for
otherwise unemployed people. |
![](../../_themes/biocontrol/bullet2.gif) | Weeds which cause allergies, dermatitis and poisoning may be
considered to provide physicians and veterinarians with
afflicted patients.
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