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

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

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

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

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

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

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

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

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

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

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

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