Target pest: Rubus fruticosus (Rosales: Rosaceae), blackberry
Agent introduced: Phragmidium violaceum (Pucciniales: Phragmidiaceae)
Landcare Research (2014c) - self-introduced.
AgPest (accessed 28 Feb 2022) - native to Europe, the rust was first discovered in New Zealand in 1990 and is thought to have blown over from Australia.
Landcare Research (2014c) - common in areas where susceptible plants occur.
Impacts on target:
Landcare Research (2014c) - can be damaging but many plants are resistant.
Impacts on non-targets:
Waipara et al. (2009) - to assess non-target impacts of pathogenic weed biocontrol agents, including Phragmidium violaceum, introduced to New Zealand, nationwide surveys were conducted 2000-2009, focussing on plants closely related to the target weeds. Non-target attack by P. violaceum was confirmed on the endemic Rubus cissoides (bush lawyer) and evergreen (cut leaf) blackberry (Rubus laciniatus). Visible infection of R. cissoides was infrequent, with the rust being found on only 2 out of the 132 (1.5%) plants examined during 2004-2006, despite heavy infection of the target plant (R. fruticosis) at the same site, and no infection being recorded in subsequent checks (2008-2009). The two infected R. cissoides plants displayed only minor disease symptoms; to date, P. violaceum is having a negligible impact on this native species. Field infection of P. violaceum on R. cissoides was predicted from previous host range testing when the pathogen was first being considered as a potential biocontrol agent for blackberry in Australia. That testing also showed the New Zealand native Rubus schmidelioides to be susceptible, though the present field surveys did not detect any non-target damage on that species. Phragmidium violaceum was not deliberately introduced to New Zealand and the strict host specificity protocols required by EPA would have most likely precluded its official release here.
Landcare Research (2014c). Who's who in biocontrol of weeds? What's new in biological control of weeds? 69: 10-11 https://www.landcareresearch.co.nz/assets/Publications/Weed-biocontrol/WhatsNew69.pdf
Waipara NW, Barton J, Smith LA, Harman HM, Winks CJ, Massey B, Wilkie JP, Gianotti AF, Cripps MG (2009). Safety in New Zealand weed biocontrol: a nationwide pathogen survey for impacts on non-target plants. New Zealand Plant Protection 62: 41-49