Lessons from Insect and Disease Impacts on Radiata Pine (Pinus Radiata D.Don) Plantations in New Zealand over the Last Hundred Years

Abstract

HIGHLIGHTS Radiata pine remains the greatly preferred medium density softwood in New Zealand although with climate change it may become more marginal on some sites. Past biotic attacks on New Zealand's radiata pine plantations have either abated or are easily managed, but while the probability of a biotic catastrophe appears low, it is not zero. Despite their impact on growth rates, radiata pine productivity has increased since it was widely planted. The opportunity costs and the associated risks make major species diversification currently inadvisable, despite New Zealand's very high reliance on radiata pine. A broad defensive strategy, including strong biosecurity infrastructure, is strongly recommended. SUMMARY The impacts of past and potential insect pests and diseases in New Zealand's radiata pine plantations are reviewed. Invariably their impacts have decreased with time or can be easily managed. Despite past biotic impacts. growth rates have increased over the last 100 years. Pitch pine canker (PPC) is perceived as the greatest new threat. PPC's impact in California, Spain, Portugal, South Africa and Chile suggests that in New Zealand it would become a nursery problem. Radiata pine remains the best medium-density softwood for New Zealand although climate change may alter the site limits. While a biotic catastrophe, despite its low probability, remains an important risk, this risk is outweighed by the opportunity costs and risks associated with diversifying into alternative species. A strong biosecurity infrastructure is vital, as is maintaining a broad genetic base from which to breed resistance. Large plantation estates should develop defensive strategies against new biotic invasions. .