Farm Forestry New Zealand
PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND
Reduction of Fusarium Infection of Pinus radiata Seed
Date: September, 1999
Author: M. A. Dick and N. J. Turner
Publication: Landcare Research Contract Report LC9798/127
Project reference: FHRC 1998-05
Executive summary:
Overseas
In experimental programmes fungicide and heat treatments have been shown to markedly reduce, but not eliminate, Fusarium spp. from infested seedlots from a range of plants.
Levels of Fusarium subglutinans f. sp. pini in seedlings germinating from infected Pinus palustris seed were markedly reduced, but not eliminated, by thiabendazole fungicides applied in the organic solvent dimethyl sulphoxide.
New Zealand
A hot water treatment of 62?C for 30 min had no significant effect on germination of Pinus radiata seed or of subsequent seedling growth. An increase of 1?C reduced germination from 87% to 17% (when treated for 30 min).
A number of fungal species, all non–pathogens, naturally contaminate Pinus radiata seed. Some species were eliminated by the heat treatment (62?C for 30 min), others were unaffected.
Two organic solvents, dimethyl sulphoxide (DMSO) and polyethylene glycol (PEG) did not have any independent inhibitory effect on either fungal growth, or on the germination and subsequent growth of P. radiata seed.
In in vitro bioassay studies with 6 fungicides/fungicide mixes:
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benomyl, triadimenol/imazalil and benzimidazole/carboxin/thiram (15000mg a.i./ml) pevented growth of Fusarium oxysporum and F. subglutinans species
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potassium phosphite (40,000, 120,000 and 200,000mg a.i./ml) and fludioxonil (15000mg a.i./ml.) inhibited, but did not prevent, growth of the Fusarium spp.
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azoxystrobilurin (15000mg a.i./ml.) had no effect on growth of Fusarium spp.
At 15000mg a.i.lml benomyl delayed germination of P. radiata seed, markedly when applied in water and slightly less so when applied in organic solvents.
At 15000mg a.i.lml triadimenol/imazalil delayed germination of P. radiata seed when applied in water but not when applied in organic solvents.
Recommendations
There is considerable scope for refining dosages, replicating treatments and comparing the effect of seed source, but sufficient information has been gathered to proceed with tests on infected seed.
The 3 fungicide treatments effective against Fusarium in bioassay should be trialed with Fusarium –infected seed in California.
In view of reports from the USA thiabendazole treatments should also be trialed.
Hot water thermotherapy should not be pursued.
Full report is available from:
Crop & Food Research
Private bag 4704
Christchurch
New Zealand
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