Whitetop weed

• Whitetop weed, Santa-Maria, Santa Maria feverfew

• Disturbed habitats such as road and rail verges, abandoned farmland and waste ground, river and stream banks, urbans areas and gardens and cultivated and pasture lands.

• Parthenium hysterophorus was accidentally introduced to India from the USA in the 1950s and has since spread throughout central Asia, mainly via roadsides although many other vectors are likely to be involved. It appears to have been accidentally introduced to Australia with US aircraft parts during the Second World War and later as a seed contaminant. It became established in Africa in the 1970s, possibly from contamination of wheat seed delivered as food aid. 
• Parthenium hysterophorus has not been recorded in the British Isles and is unlikely to occur under current climatic conditions.

• Parthenium hysterophorus is regulated as a quarantine pest in Europe under the EU IAS Regulation introduced in 2014. This restricts sale and movement and requires signatory Governments to undertake eradication programmes. 

• Parthenium hysterophorus has very few natural predators and livestock do not eat it and as a consequence it can disrupt native food chains. It also has a toxic (allelopathic) effect on soil flora and fauna, and replaces or suppresses native vegetation in a wide range of habitats.

• Parthenium hysterophorus is a toxic weed that can cause a range of mild to serious allergenic reactions, including hay-fever, rhinitis, bronchial asthma, itching, eczema, dermatitis, especially amongst agricultural workers or city-dwellers exposed to high levels of pollen and debris (trichomes) in heavily infested areas.

Economic Impact

Parthenium hysterophorus is a toxic weed that can cause a range of mild to serious allergenic reactions, including hay-fever, rhinitis, bronchial asthma, itching, eczema, dermatitis, especially amongst agricultural workers or city-dwellers exposed to high levels of pollen and debris (trichomes) in heavily infested areas.

• It has not been found in Northern Ireland.

Methods for prevention

• Ensure that it is not spread from already invaded areas.
• Do not transplant from one area to another.
• Report all sightings. 
• Do not swap cuttings or seedlings with friends, especially if you can't identify the plant.
• Plant native species instead.

• CABI 2017. Invasive Species Compendium: Parthenium hysterophorus (Parthenium Weed - Parthenium weed portal
• EPPO 2014. Pest Risk Analysis for Parthenium hysterophorus (Parthenium Weed) -  https:www.eppo.intQUARANTINEPest_Risk_AnalysisPRAdocs_plants15-21049_PRA_record_Parthenium_hysterophorus.pdf.

• This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.