Research likely to reduce farmers thistle problems

Media Release November 1 2000

Research likely to reduce farmers thistle problems

The prickly issue of thistles encroaching on farmland could soon be reduced thanks to the work of HortResearch scientist Adrian Spiers.

Thistles cause at least $50 million a year in lost farm production but the discovery of a new thistle-killing fungus and initial research by Dr Spiers means farmers’ thistle problems could soon decrease.

The first trials on a Pahiatua farm, where the naturally occurring fungus was discovered last year, were promising with many of the thistles on Donald Schnell’s property exhibiting infection and die-back after only one season of spreading the fungus. “So far the trials on one farm have been encouraging enough for us to think we are onto something,” Dr Spiers said.

Further field tests are in progress with the start of the new growing season. Starting this month, trials will begin in conjunction with the Ohinewai Farm Study Group (South of Hamilton) on 10 farms. If the results of this season’s tests are successful, Dr Spiers said he would progress toward growing the fungus to sell to all farmers.

Because the fungus spreads of its own accord Dr Spiers said after two or three years on the market the spray would no longer be needed as the fungus would be established throughout New Zealand.

Trials so far have shown that all California thistles appear to be susceptible to the fungus. “It is unlikely the thistles will build an immunity to the fungus.” The fungus also kills Scotch thistles and further tests are taking place to see if other varieties will be affected in a similar way. Initial research has shown the fungus does not effect other species such as native plants, peas, clover or grass.

A Dutch expert has identified the fungus as being Phoma exigua var. exigua, which is common in New Zealand but the strain that is killing the thistles is new.

Dr Spiers said the fungus may be used in other countries as a bio-control tool if future tests continue to prove successful.

In another step forward in the battle against thistles Dr Spiers has identified a leaf disease, Septoria, naturally occurring in thistles. Although this disease commonly affects Celery plants it has not been found on thistles before. Dr Spiers is researching whether it could be used to control them.

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For further information contact: Dr Adrian Spiers, HortResearch, Tel: 06 356 8080 Ext 7748. Fax: 06 354 6731. Email: ASpiers@Hort.cri.nz

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