A more co-ordinated effort has begun to tackle the spread of wilding conifers that have become major plant pests in parts of the country.
The Ministry for Primary Industries (MPI) is leading the development of a national control strategy.
A report commissioned by the ministry has identified 10 introduced conifers at the root of the problem, costing millions of dollars a year to control.
They include dominant commercial plantation varieties, like pinus radiata and douglas fir, that are self-seeding and colonising areas where they are not wanted.
The report estimates the pest trees have spread over more than 800,000 hectares of the South Island and 300,000 in the North.
Senior adviser in the MPI national co-ordination team Sherman Smith says the national strategy is the main recommendation to come out of the report.
He says MPI will work with a range of parties including the forestry industry, federated farmers, private landowners and councils.
Mr Smith says it will draw in all the pieces of legislation relating to wilding conifers to try to achieve a common goal to ensure that all parties are aligned in the work they are doing.