Abstract. Phaeocryptopus gaeumannii, the causal agent of Swiss needle cast disease, is widely distributed throughout New Zealand, where the disease may cause significant growth losses in Douglas-fir (Pseudotsuga menziesii) plantations. In western Oregon, where the pathogen is native, pathogen abundance and disease severity are correlated with mean daily winter temperatures and spring moisture, enabling the development of climate-based disease prediction models. The distribution of P. gaeumannii and severity of Swiss needle cast was surveyed in 16 Douglas-fir plantations throughout New Zealand in 2005. Retention of foliage was assessed in the field and samples of 1-and 2-year-old needles were collected for assessment of P. gaeumannii abundance. Foliage retention and abundance of P. gaeumannii varied across sites. Less colonisation by P. gaeumannii and greater needle retention was found in the South Island. Abundance of P. gaeumannii was found to be positively correlated with August minimum temperature and June average temperature, and showed a similar relationship to winter temperature as observed in western Oregon. These data will be used to derive a disease prediction model for Swiss needle cast in New Zealand that can be used to guide further research and provide short-and long-term disease risk predictions and cost/benefit analyses.

No abstract

No abstract

No abstract

Phaeocryptopus gaeumannii, the cause of Swiss needle-cast, is widely distributed in plantations of Douglas-fir in many parts of the world. Nevertheless, information remains limited on its precise effect on stand growth, particularly in relation to regional climate, and on its consequent economic cost. In New Zealand, the spread of P. gaeumannii over a period of ≈30 years following its discovery in 1959 was closely monitored, and the timing of its arrival in different forests is known. This information was coupled with data from permanent sample plots in order to quantify the associated historical growth increment loss. Analyses revealed a steady decline in growth rate over the period from the first appearance of P. gaeumannii to a point when it stabilized at a lower increment level 14 to 20 years later. The cumulative mean reduction was 25% for mean top height, 27% for basal area, and 32% for stem volume. Volume growth rate decline was greater in the North Island (35%) than the South Island (23%) of New Zealand. These reductions in volume growth are estimated to equate to a loss in net present value of $NZ2,620 ha(-1) and $NZ1,470 ha(-1) for the North and South Islands, respectively, using a discount rate of 6%. Mortality did not increase as a result of infection by P. gaeumannii. The disease had less effect on cooler sites, especially those with low spring minimum temperatures (P < 0.001). Negligible growth decline occurred on sites with daily minimum October temperatures averaging <3.2°C.