Fewer pines with blight in Westland

Press, 25 July 1984, Page 14

Fewer pines with blight in Westland

Fewer radiata pine trees have been affected by Dothistroma needle blight in central Westland this year than last year, according to two forest health officers, Messrs Bob Smith and Colin Barr, of the Forest Research Institute at Rangiora. The two men recently visited Westland to make the annual assessment of the level of infection. According to Mr Barr, a double spraying with the fungicide, copper oxychloride, last year, has probably reduced the level of infection this year. The fungicide was sprayed from the air over the forests in the Hokitika and Greymouth areas in October and in Novem-ber-December. The spray killed the spores when most of them were multiplying, and protected the foliage against new infection for four to six weeks, said Mr Barr. The assessments of infection levels are done in winter because when the trees are dormant it is easier to see, from the air, the bands of brick red on the needle which are the symptom of infection by the fungus.

“When you get a flush of new growth in summer you get a lot of other, colours coming on,” said Mr Barr. The two men also visit Westland for a week each month to check other aspects of forest health. “The timber inspectors at ports throughout New Zealand try to prevent any exotic insects or disease organisms from entering the country,” said Mr Smith. “We are the second line of defence. If anything gets past we may be able to pick it up in the forests.” Mr Smith said that during a recent inspection they had noted some defoliation, yellowing, and short needles in the upper third of some radiata pine trees more than 15 years old. The cause of this was not yet known. “It could be a result of a combination of factors, such as nutrients, climatic conditions, and disease,” said Mr Smith. According to material recently published by the Forest Service, Pinus radiata is expected to show some resistance to Dothistroma once it is older than about 10 years.