A recent survey of the occurrence of sapstain fungi in New Zealand, conducted at The University of Waikato, provided the opportunity to examine fungicidal tolerance amongst new isolates. It also enabled a comparison of tolerance amongst new isolates with those used in routine antisapstain screening trials at Forest Research. A rapid antisapstain laboratory disc trial was used to determine the extent of fungal growth after three weeks on radiata pine treated with various commercial antisapstain formulations, which was then used as an indicator of susceptibility or tolerance. The results showed that under laboratory conditions, susceptibility to antisapstain formulations varied greatly, both between species, and between isolates of the same species. None of the formulations tested gave good control of all the isolates when tested at commercial usage rates. The significance of these results is discussed in terms of design of laboratory antisapstain trials and relevance in the field.

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