Project reference: 1998-05
Pine Pitch Canker - Seed Treatments and Seed Testing
Recent results from researchers in California (Dr T Gordon pers. comm.) indicate that a percentage of the Pinus radiata seed collected from pine pitch canker infected areas carries a deep-seated infection of Fusarium subglutinans f sp. pini which cannot be detected by the seed screening procedures currently in use in New Zealand. Furthermore seedlings grown from such seed may not manifest this latent infection for several months following germination. This information has led MAF Quarantine to impose further restrictions on the importation of pine seed from pitch canker infected areas. The Chief Plants Officer has approved the categorisation of F. subglutinans f. sp. pini as a Risk Group 2 pest. All seed imports will now require Level 3 (high security) post entry quarantine screening. This categorisation will severely curtail the importation into New Zealand of genetic material as seed from a number of locations.
An effective seed treatment which can demonstrably eliminate seed infections may lead to a relaxation of these restrictions. In Australia AQIS requires heat treatment of pine seed imported from North America before release. However it is not known whether this treatment will eradicate F. subgIutinans f. sp. pini from conifer seeds.
We propose contracting a programme in California to heat-treat F. subglutinans f. sp. pini infested seedlots with different temperature/time combinations to test for the effectiveness of eliminating the fungus Preliminary evaluation of the limits imposed by reduction of germination percentages would be carried out in New Zealand. The effectiveness of a recently developed fungicide with putative eradicant properties would also be tested in the programme.
As there remains some doubt about the potential for Douglas fir seed to carry F. subglutinans f. sp. pini the programme could be expanded to evaluate the risk that this seed poses. Douglas fir seed would be collected from pitch canker-infected areas where Douglas fir and radiata pine grow in mixed stands to test for both external and internally-borne infection.