DISEASED TREES

Press, Volume CXIV, Issue 33512, 18 April 1974, Page 12

DISEASED TREES

New poplars chosen

Types of poplar trees most resistant to the leaf rust disease that is spreading throughout New Zealand are being selected to restock catchment board nurseries. .Mr C. Van Kraayenoord. the scientist in charge of the Ministry of Works and Development’s plant materials centre at Palmerston North, said in a report to the Sol Conservation and Rivers Control Council that the restocking could take up to eight years.

The rust has affected trees throughout the North Island and is rapidlv spreading throughout the South Island Half the West Coast has beer affected and the most recent sighting is .at Timaru. It i< expected to reach Otago be fore winter. The rust was discovered >r Northland a year ago and wa.< confirmed as being of Nortii American origin, hut short N afterwards a European rust was diyovered around New Plymouth. The European rust is more damaging and has s greater wintering-over ability, and has affected more poplar.t than the American strain. Young trees, up to five years old. are most susceptible to the disease. Affected trees develop a weakened root system because of the loss of leaves which are the source of nutrient for the roots. Poplar trees are used extensively in New Zealand for soil conservation. Mr Van Kraayenoord said that other trees were available for conservation work, but were liable to damage from stock. All poplars are known to be susceptible to the rust bu> some are more resistant than others. Of 15.000 seedlings to be planted out this year, it is hoped that about half will show some degree of resistance.