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Published: 2003-04-15 00:00:00

Environment Waikato is working with the Department of Conservation, Ministry of Defence and trustees of Maori land blocks to control the spread of contorta pine in the central North Island.

About 2,000 ha of contorta pine trees were planted in the Karioi Forest during the 1920s and they have been seeding over tussock land next to the Desert Rd. Their seedlings compete with existing vegetation, and the battle to control their spread began in the 1960s.

Taupo area Plant Pest Officer Kevin Loe said the ability of contorta and lodegepole pine to rapidly spread and colonise new areas, especially tussock lands, had led to the infestation of a further 1,300 ha of land in the mid 1970s.

“Although other pines eventually spread, contorta pine is always first to do so, perhaps because in its natural habitat, it is an aggressive species which survives fires.

“The densities of the trees has been reduced to very low numbers as the result of our efforts and the best way to work towards further reduction is to use a helicopter to systematically scour these areas to locate and destroy the trees.”

Environment Waikato has funded about $5,000 a year for the past three years for helicopter hire for control on unoccupied Maori lands infested with contorta. DoC and the Ministry of Defence have spent another $50,000 working on their own land to control the pest. Excellent co-operation between the Crown agencies, landowners and Environment Waikato had brought about this good result.

“The cost per tree ranges from $40 to $3 depending on the nature of the infestation and how remote their location is. Control programs are designed to break the seedling cycle, and require areas to be covered on a three-year rotation as contorta can produce viable seed at four to five years old.

“With the substantial reductions being made, the threat of a contorta forest dominating the Desert Rd and to the summit of Ruapehu will disappear,” he said.