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   Ageratum conyzoides (草本植物) English   
生態 分佈 管理 影響 參考資料 聯繫


         一般影響

    農業:藿香蓟(Ageratum conyzoides)是許多一年生和多年生農作物的雜草,據報告,是許多農作物疾病的宿主(Ekeleme等人, 2005)。此雜草會干擾農作物生長和產量,因此對生態和經濟產生重大影響(Singh 等人, 2001,Batish等人, 2009)。例如,在亞洲,水稻產量一直與藿香蓟(A. conyzoides)密度負相關(羅德等人, 1998)。有研究顯示,此雜草具有植物相剋作用,但是,幼苗對光線的競爭似乎是干擾作物的主要方式(Ekeleme等人, 2005)。
    植物相剋:植物相剋作用是一種生物干擾,一種植物將生物活性代謝物釋放到周圍的環境,對附近的植被生長,產生不利的影響,並對釋放的植物產生選擇優勢(Batish等人, 2009a)。藿香蓟(A. conyzoides)的揮發性物質,包括早熟素及其衍生物單萜和倍半萜,會產生光抑制和植物相剋作用。有許多證據顯示,藿香蓟(A. conyzoides)產生的化學物質,會經由其根莖系統,抑制其他植物發芽和生長。藿香蓟(A. conyzoides)新鮮的葉片和揮發性油,會抑制各種作物幼苗生長(Kong等人,99),包括花生,紅蘿蔔,黃瓜和黑麥草(Kong Hu & Xu 2002)。研究顯示,藿香蓟(A. conyzoides)的芽萃取物,會抑制發芽尾穗莧中,馬唐和生菜(萵苣)。答:萃取物藿香蓟(A. conyzoides)抑制小麥和水稻的種子發芽(Jha & Dhakal 1990,Ming 1999)。藿香蓟(A. conyzoides)葉片分泌和殘留的酚,會干擾小麥的生長和發展(Singh 等人, 2003,Batish等人, 2009a)。生長在藿香蓟(A. conyzoides)根際土壤中的水稻,其根與芽的長度和生物量會顯著減少18至30%(Batish等人, 2009a)。藿香蓟(A. conyzoides)的腐葉會影響水稻初期生長(Batish等人, 2009b)。最後,藿香蓟(A. conyzoides)會減少鷹嘴豆生長發育和結瘤(Batish等人, 2004)。當植物生長在營養不足的環境,和因為真菌感染或蚜蟲啃食而減少時,光抑制和植物相剋作用會提高(Kong Hu & Xu 2002)。
    植物病原傳播:Kashina、Mabagala和Mpunami(2003)在坦桑尼亞附近的番茄農場發現,藿香蓟(A. conyzoides)是「番茄黃化捲葉病毒」的宿主雜草和病原庫(Kashina,Mabagala & Mpunami 2003)。藿香蓟(A. conyzoides)可能是「番茄黃化捲葉病毒」重要的病原庫,因為它在番茄農場內數量很多,它與粉蝨載體共域,粉蝨會自然地感染這種病毒。在其他地方,藿香蓟(A. conyzoides)已被確定為「藿香黃脈病毒」的宿主
    人類健康:藿香蓟(A. conyzoides)會造成某些人的過敏反應(Negi & Hajra 2007),並可能危害人類健康(Kohli & Batish 1996)。
    喜馬拉雅植物族群案例研究:Shivilak位於印度北部喜馬拉雅山區,素以豐富的植物多樣性聞名。但是,藿香蓟(A. conyzoides)對天然植物草原結構和森林社群以及自然生態系統的動態,造成威脅(Singh 等人,;Dogra 等人, 2009)。此雜草取代了原生草被和重要的藥用植物,研究顯示它降低了生物量,生物多樣性,使植群單一化(Dogra 等人, 2009)。它還會負面地干擾農作物(小麥,鷹嘴豆,大米,玉米和甘蔗)。



         地點特有的影響:
    Asia English 
    傳播疾病: Yellow vein disease of Ageratum conyzoides, a weed species that is widely distributed throughout Asia, has been attributed to infection by the geminivirus Ageratum yellow vein virus (AYVV). Members of the Geminiviridae genus Begomovirus (Briddon and Markham 1995, in Saunders & Stanley 1999) are transmitted by the whitefly Bemisia tabaci (Gennadius) to a wide range of vegetable and fibre crops worldwide in which they cause serious diseases (Brown 1994, in Saunders & Stanley 1999).
    A. conyzoides plants coinfected with AYVV DNA A and DNA 1 remain asymptomatic, indicating that additional factors are required to elicit yellow vein disease. The author's results provide direct evidence for recombination between distinct families of plant single-stranded DNA viruses and suggest that coinfection by geminivirus and nanovirus-like pathogens may be a widespread phenomenon. The ability of plant DNA viruses to recombine in this way may greatly increase their scope for diversification.
    South East Asia (Asia) English 
    傳播疾病: Weed species are believed to act as reservoir hosts for many economically important plant viral diseases. A. conyzoides, a weed that occurs throughout South East Asia, frequently exhibits yellow vein symptoms that are associated with infection by Ageratum Yellow Vein Virus (Saunders et al. 2000).

    農業: A. conyzoides is one of the most dominant weeds in upland crop areas of South East Asia (Kato-Noguchi 2001).
    South China (China) English 
    農業: The fresh leaves and volatile oil of A. conyzoides in south China were found to be highly inhibitory to seedling growth of various cultivated crops, especially in an adverse habitat.
    India English 
    其他: A. conyzoides poses a human health hazard also (Kohli & Batish 1996). A number of health problems in human beings and toxicity to livestock have been reported. These include contact dermatitis, skin irritation, nausea, giddiness (due to their pungent smell), and respiratory problems such as bronchitis and asthma.

    農業: A. conyzoides interferes with crops and causes yield reductions of major staple crops of India (Kohli et al. 2006). It forms thick monospecific stands at the expense of commonly grown crop species such as wheat, chickpea, rice and maize (Kohli et al. 2006, in Batish et al. 2009a). When it invades rangeland areas, it out competes native grasses causing scarcity of fodder (Kohli et al. 2006), thereby putting livestock under starvation conditions. Severe infestations by A. conyzoides reduces crop yields significantly and to such a low level that some farmers in the lower Shivalik ranges of the Himalayas have had to abandon their fields (Batish et al. 2004; Kohli & Batish 1996).

    降低本地生物多樣性: Rich medicinal plants, an important resource, are being out-competed by A. conyzoides (Kohli & Batish 1996).
    Shivalik Ranges (India) English 
    人類健康: A. conyzoides presents a health hazard to humans (Batish 2008).

    改變水文: A. conyzoides chokes water channels (Singh Undated).

    改變營養機制: A. conyzoides deteriorates soil quality (Batish 2008). The weed is strongly allelopathic and adversely affects crop productivity through its allelochemicals. Almost all parts of the weed (stem, roots, leaves, inflorescence), are known to cause allelopathic effects. Volatile allelochemicals include Precocene I, Precocene II and Caryophyllene etc. Non-volatile phenolic acids include gallic acid, coumalic acid, and protocatechuic acid, p-hydroxybenzoic acid, p-coumaric acid, sinapic acid and benzoic acid.
    Dogra and colleagues (2009) found that the amount of phenolics in the soil was 41% higher in A. conyzoides-invaded areas than in control areas. The pH in the A. conyzoides-invaded areas was slightly higher than in the control areas. The conductivity of the ions was 31% more in the A. conyzoides invaded area as compared to control. Percent organic carbon and organic matter also increased in the invaded area by nearly 49%. The increase in the available nitrogen content was highest among all other nutrients. It increased by 57% in the invaded area. The amount of available phosphorus, potassium and sodium were more by 48%, 38% and 25% respectively in the A. conyzoides-invaded soil as compared to the control soil. The amount of available calcium, magnesium and chloride were more by 37%, 32% and 33% respectively in the A. conyzoides-invaded soil as compared to the control soil (Dogra et al 2009).

    棲地改變: The invasion of these three invasive plant species (A. conyzoides, L. camara, P. hysterophorus) highly reduces the available habitats or niches for the growth of other useful plant species. They are responsible for the loss of productivity and diversity of species in the invaded areas. They drastically alter the structure, function and dynamics of invaded habitats (Dogra, Kohli & Sood 2009).

    生態系統變化: Dogra and colleagues (2009) evaluated the impact of A. conyzoides on the diversity and floristic compositions of native species. It was found that as compared to control, in the Ageratum invaded area:
    • The average number of plant species was reduced by 32% (81 species in the control area as compared to 55 in Ageratum invaded areas);
    • Margalef's index of species richness, alpha species diversity and evenness index were reduced by 37%, 41% and 15%, respectively;
    • The fresh and dry biomass of plants was significantly reduced by 52% and 48%, respectively ;
    • The number of abundant species (N1) and very abundant species (N2) were also significantly reduced; and
    • The value of index of dominance was higher, indicating that communities were homogenous in nature and dominated by a single species (compared with un-invaded communities which showed more heterogeneity).
    It was concluded that invasion by A. conyzoides drastically affects the productivity, composition and diversity of the invaded areas in Shivalik hills of Hamirpur district.

    競爭: A. conyzoides replaces other vegetation including native grasses (Batish 2008; Singh Undated).

    農業: The weed is a problem for farmers, ecologists, locals, environmentalists and animals (Batish 2008). It is a troublesome weed of cultivated lands. A. conyzoides is responsible for replacing grasses in pastures and causing fodder loss (as cattle do not feed on the weed), deteriorating soil quality and reducing crop quality and yield (wheat, chickpea, rice, maize, and sugarcane) (Singh Undated). A. conyzoides also adversely affects animal health; and causes hindrances to ploughing (Batish 2008).

    降低本地生物多樣性: Dogra and colleagues (2009) found that A. conyzoides, L. camara and P. hysterophorus reduce species diversity and composition in the Shivaliks. The decrease in diversity indices and biomass in the invaded sites show that plant communities become less productive in response to these invasive plant species in the lower Shivaliks of Himachal Pradesh, India (Dogra et al. 2009). Batish (2008) found that A. conyzoides adversely affects biodiversity and checks the growth of grasses and other weeds. A. conyzoides can result in an up to 50% decrease in average dry biomass (grams per meter squared) and can cause an over 30% reduction in total species number (Batish 2008). Singh and colleagues (Undated) found that, compared with controls, native vegetation in A. conyzoides-infested habitats was significantly reduced (including numbers of species, plant density and biomass) especially in wastelands and grassland, indicating that invasion by A. conyzoides reduces plant biodiversity.

    Dogra and colleagues (2009) found that the number of herbs decreased sharply (as compared to other life forms) in the A. conyzoides-invaded areas. Results showed that herbal vegetation was affected maximally as compared to other vegetation types. Major medicinal plants affected by the invasion of A. conyzoides were Murraya koenigii, Dichanthium annulatum, Cynodon dactylon, Trifolium repens, Achyranthes aspera, Adhatoda vasica and Carissa carandas (Dogra et al. 2009).

    West Bengal (India) English 
    農業: A. conyzoides is a crop weed in the plains of Eastern Himalayan region of West Bengal. It is an unwanted plant in the crop land that competes for nutrients, water and space.
    Doon Valley (India) English 
    其他: It creates allergic problems.

    改變林火機制: A. conyzoides introduced from tropical America has expanded at an alarming rate, especially in agricultural fields, along footpaths, road sides and in gardens of heavy peat content. Its dominance in fire-burn areas makes it appear a permanent denizen of India.

    降低本地生物多樣性: It is harmful to native floristic composition.
    Dodoma (Tanzania, United Republic of) English 
    傳播疾病: Kashina, Mabagala and Mpunami (2003) found that A. conyzoides is a new weed host and disease reservoir of the Tomato yellow leaf curl Tanzania virus near tomato farms in Dodoma, Tanzania. A. conyzoides and Sida acuta are potentially important TYLCTZV reservoirs because they occur in abundant numbers within the tomato farms, they are associated with whitefly vectors, and were found naturally infected with TYLCTZV.



ISSG Landcare Research NBII IUCN University of Auckland