1. 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

2. Parthenium weed distribution in South Africa (2007)
McConnachie et al 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 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 Australian isolate imported and established
Released in South Africa under permit in late 2010
Optimal infection at 22°C for 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 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 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