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 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-Nata l

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