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Published: 2008-10-06 00:00:00

Up to 60,000 possums are estimated to have been killed in a highly successful pest control operation carried out on behalf of Environment Waikato in the Waimai Valley area, north of Raglan.

The operation is also expected to have killed a significant number of rats which, like possums, decimate bird life.

A spokesman for Waimai Valley landowners involved with the project, Alastair Reeves, said: "I am absolutely rapt with the possum control. We have never lived without possums and as a result of this project we see fruit on our trees now and no possums on the road anymore.

"It has been great to be involved in this project and it has been really nice to see EW and the community working together on something positive in our area."

Another landowner said this year was the first time in more than 30 years that she had been able to pick mandarins from a tree on her property – previously the possums had always got to them before they ripened.

Besides protecting bird life, fruit trees, native plants and pine forests, the pest control over 15,516 hectares, between February and August, will benefit agricultural production in the predominantly sheep and beef farming area, as possums compete for feed with cattle and sheep.

The work will also help stop possums eating vegetation planted to prevent erosion and keep nutrients out of waterways, said Environment Waikato biosecurity officer Dave Hodges.

The operation, carried out with the co-operation of more than 80 landowners, followed requests for pest control from farmers.

"We are really pleased at the positive results which will help native birds thrive, support more efficient farm production and protect our soil and waterways," Mr Hodges said.

The possum control used a range of methods - including encapsulated cyanide, cholecalciferol and brodifacoum – applied by ground-based operators. Cholecalciferol and brodifacoum are also highly effective against rats.

The aim at the end of the operation was to have only five possums caught for every 100 monitoring traps, compared to more than 36 per 100 traps before the operation started. The results exceeded the target with an average of 1.2 possums caught per 100 traps during post-operation monitoring.

"Based on these numbers, our contactor, Farm and Forest Pest Services, estimates as many as 55,000-60,000 possums may have been killed," Mr Hodges said.

"We expect this work will mean possum numbers are kept low in the area for a significant period."

More possum control will be carried out in the Waimai Valley when necessary. The actual timing will be dependant on the results of possum trend monitoring that EW will carry out in about 18 months time.

Meanwhile, EW plans to carry out possum control work in the areas north and south of the Waimai Valley over the next few years. This will include through Woodleigh - Waikaretu and Te Akau South.