A "big and bad" mast year may see the money that's been allocated to tackle it spreading thin.

In a mast year, trees produce large amounts of seeds and fruit which can boost pest numbers.

DOC announced $38 million to combat it, but they're already having to re-apply poison in areas because of growing rat numbers.

Forest and Bird's Kevin Hackwell told Mike Hosking DOC should use extra funding for future years if it's under pressure.

"We need to pull forward the money from the future year, when we know we're not going to need, not going to need, let's get it right this time."

When the mast ends, rats and stoats tend to turn to native birds, lizards and insects to feast on.

Hackwell says DOC must ensure that the money allocated this year is enough.

"The threat to our native species is very real and the ability to do the pest control is great, we've developed these techniques and are very good at it. If we're overwhelmed we just need to get the extra resources."