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Alana den Breeyen ARC-PPRI Weeds Pathology Unit Stellenbosch South Africa 7600

Update on the rust fungi implemented as biocontrol agents against Parthenium weed in South Africa. Alana den Breeyen ARC-PPRI Weeds Pathology Unit Stellenbosch South Africa 7600. Parthenium weed distribution in South Africa (2007). McConnachie et al. 2011 Weed Research 51: 71-84.

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Alana den Breeyen ARC-PPRI Weeds Pathology Unit Stellenbosch South Africa 7600

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  1. Update on the rust fungi implemented as biocontrol agents against Parthenium weed in South Africa Alana den Breeyen ARC-PPRI Weeds Pathology Unit Stellenbosch South Africa 7600

  2. Parthenium weed distribution in South Africa (2007) McConnachie et al. 2011 Weed Research 51: 71-84

  3. Puccinia abrupta ‘winter rust’ • First identified in 1995 (Brits area) • Introduced with the host plant as early as 1880s? Or subsequent plant introductions • Optimal infection at 18°C for 12-24 h; range between 15 – 20°C • Tolerates relatively ‘low’ temperatures and more ‘arid’ conditions • Easier to ‘harvest’ spores for mass production • Prevalent in field from May - October

  4. Puccinia abrupta ‘winter rust’ • Increased incidences of the winter rust observed in 2013 in KZN and Mpumalanga provinces

  5. Puccinia xanthii ‘summer rust’ • In 2007 - Australian isolate imported and established • Released in South Africa under permit in late 2010 • Optimal infection at 22°C for 12-24 h; >80% humidity; ranges from 20 – 25°C • Tolerates relatively ‘high’ temperatures if moisture available • Mass production complicated by ‘sitting teliospores’ • Prevalent in field from November – April

  6. Mass production – P. xanthii P. xanthii pustules = culture Mist room: optimal infection @ 22°C for 24h

  7. Mass production facilities Mass-production facility was setup at the Lowveld Pest, Disease and Variety Control offices in Malelane, Mpumalanga Mass-rearing centre is based at the South African Sugarcane Research Institute (SASRI) in Mount Edgecombe in KwaZulu-Natal

  8. Field releases • Parthenium plants optimally infected in glasshouse with ‘summer rust’ • 14 d after inoculation, infected plants either mailed to interested parties overnight • whole plants packed in plastic bags filled with vermiculite and wetting agent • packed in polystyrene box, sealed and shipped • Or researchers travel with infected plants in cooler box • Whole infected plants planted out in the field • 6-10 plants per release site @ 1 m apart (‘trojan plant’) • Planting should take place in late afternoon when temp. < 25°C; just before or after rain event

  9. P. xanthii releases & establishment 2013/14 • First successful establishment of P. xanthii in KZN in 2014 KwaZulu-Natal

  10. P. xanthii releases & establishment 2013/14 • Establishment and spread of P. xanthii in Malelane area in Mpumalanga(perennial Parthenium infestation)

  11. Challenges to successful releases • Lack of suitable sites for releases: • long-term [up to 3-5 years]; undisturbed & unsprayed • dense infestations >1ha; in good condition for as much of the year as possible • Preferably near perennial water • sources • Lack of mass production facilities for optimal infected plant production • Lack of implementation

  12. Conclusions • Implementation of a suite of biocontrol agents required • Key to the long-term sustainable management of parthenium weed in South Africa

  13. Acknowledgements • Funder: • Technical assistance: Gwen Samuels & Lea Orien • SASRI and Karlien Trumpelmann (TSB Sugar) – Mass production facilities

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