豬草(Ambrosia artemisiifolia L.)屬於新興外來具入侵性的有毒雜草，其花粉可引起人類花粉過敏症。由於台灣氣候環境適合豬草生長繁殖，因此對豬草的持續監測刻不容緩。金門是豬草族群最早發生之地區，目前發現已經分布於台灣本島西北部地區，包括台北縣、桃園縣、新竹縣、及苗栗縣。與1997調查結果比較，豬草並未向中南部擴散，在台中縣沿海並未發現有豬草的分布，而在台北縣的三芝鄉和石門鄉則有豬草的發生，顯示豬草有向東北擴散的趨勢。

Common ragweed (Ambrosia artemisiifolia L.), an exotic and toxic weed with invasive potential, is a main cause of "hay fever" allergies. Due to the climate and environment in Taiwan favor the propagation of common ragweed, a persistent monitoring of this weed is necessary. Although this weed was first found in Kingmen, an island outside of Taiwan, its distribution area has extended to northwest Taiwan, including Taipei, Taoyuan, Sinzhu and Miaoli counties at present. Comparing with the data observed in 1997, common ragweed has not spread into middle- and southern-Taiwan, as well as the costal area of Taichung county. However, the findings of this weed in Sanzhi and Shimen, of Taipei county, reveal that common ragweed has spread toward northeast Taiwan.