Black and White: investigations on the ecology, biology and biological control of sapstain fungi in New Zealand

This study examined ecology, colonisation, biological control and detection of sapstain fungi in New Zealand. A nationwide survey of New Zealand sapstain fungi was undertaken between 1996 and1998. In total, 1035 sites were sampled in the North and South Islands. From these collections, 1755 potential sapstain fungi were isolated and seventeen individual species were identified. The predominant sapstain fungi identified were Sphaeropsis sapinea, Ophiostoma ips, O. floccosum, O. piliferum, O. querci and Leptographium procerum. This data was subsequently evaluated according to ecological criteria, including geographical and temporal distribution of sapstain fungi. A greater diversity of sapstain fungi was found in areas of New Zealand that were primarily plantation forestry. S. sapinea was isolated during more generalised forest sampling, and from both native and plantation forests. Ophiostoma species were isolated more frequently from Pinus radiata plantations, processing plants including mills and ports and were mainly isolated from harvested forest material such as logs, wood chips, and other wood products. S. sapinea was isolated more frequently in spring and summer while Ophiostoma species predominated during autumn and winter periods, probably linked with insect vectoring. This was the first attempt to link the sapstain organisms identified in New Zealand with their overall distribution within sectors of the forest industry, in different wood species, and in different types of wood samples. New Zealand is one of the world's largest exporters of softwood logs. Exports of forest products provide 4% of New Zealand’s gross domestic product (GDP) with Japan, Korea, United States and the Philippines as major export markets for P. radiata logs. Conditions found within the holds of ships were thought likely to be ideal for the rapid colonisation of the sapstain fungi that results in dark penetrating stains. Log export research was designed to determine the extent of sapstain colonisation at specific points in the processing of logs from harvesting to the export destination. Two trials were established, in New Zealand summer and in winter, where mature P. radiata logs were harvested in New Zealand and shipped to export ports in Japan. Microclimatic conditions (temperature and relative humidity) on board the ships were recorded using data loggers both above deck and below deck. Nine species of sapstain fungi were isolated from logs during the summer trial. The most common species isolated were O. floccosum, O. querci and O. setosum. In contrast, a different combination of nine species was detected during the winter trial. S. sapinea, O. querci, O. floccosum, O. setosum and Ophiostoma piceae were most commonly isolated. The results of this study showed that the New Zealand sapstain fungi were being exported on logs. However, many of these fungi were previously recorded in Japan. In addition, no serious pathogens were detected. It was recognised during the sapstain fungal survey and export trials that a more thorough…