Blackberry in New Zealand
S.R. Pennycook, NZ Landcare Research, Private Bag 92170, Auckland, New Zealand.
In New Zealand, blackberry comprises at least 22 naturalized species and hybrids, 18 of which are widespread, in a mosaic of overlapping but imperfectly known distributions. There are four other naturalized Rubus species and five indigenous Rubus species. A small but expanding Rubus berryfruit industry, with production areas throughout the country, has an annual value of about $NZ12.5 million. Initially introduced and spread as a food source, blackberry became so successfully naturalized that it was regarded as the major weed of most of the North Island and wetter parts of the South Island during the first half of the 20th century.
Its pest status has now declined because of improved pasture management techniques and potent new herbicides, but it is still ranked as the country's fourth most serious weed, imposing problems and costs in amenity and conservation areas, in farmland (c. $NZ10.5 million per annum), and in plantation forestry (c. $NZ10 million per annum). Almost all the invertebrate pests and diseases present on blackberry are unsuitable as biological control agents because of the likelihood of collateral damage to commercial crops, and past research with imported agents has not resulted in any successes.
Phragmidium violaceum (blackberry rust) was first observed in New Zealand in 1990; it is now widely established, but its long-term impact has been mostly unspectacular and localized. Research should be directed towards identifying more efficacious rust strains with a wider host range among those blackberry species (particularly R. cissburiensis and R. cissburiensis ulmifolius) which cause the most serious problems.
Plant Protection Quarterly (1998) 13 (4) 163-174.