Reject kiwifruit 'causes feral vines'

Feral kiwifruit spread to the wild by birds feeding on reject fruit dumped or used as animal feed has become a long-term problem, a biosecurity official says.

The Bay of Plenty regional council pest plant coordinator, John Mather, today called on orchardists disposing of fruit or farmers feeding it out to livestock to take care to keep birds from feeding on the fruit.

"Unfortunately, the number of infestations has grown exponentially in the western Bay of Plenty," he said. Many of the known infestations were new, with vines less than four years old.

This was probably from thousands of tonnes of reject fruit, Mr Mather said. It was fortunate that most wild kiwifruit did not reproduce until it was five years old and seeds were viable for less than five years, he said.

If left to spread the feral vines would become increasing difficult and expensive to control.

Mr Mather warned that wild kiwifruit were serious environmental weeds: "Vines pose a danger to native bush and exotic forest, as they are very long-lived and grow prolifically, strangling and even breaking trees".

Wild kiwifruit has been growing in the native bush gullies and small exotic forestry blocks of the Te Puke district since the 1970s, and a single 30-year-old wild vine can smother 1000 square metres of scrub and young bush.

Because of this, wild kiwifruit is included in Environment Bay of Plenty's regional pest strategy as a total control plant. The feral vines had now spread further afield, around Katikati, Opotiki and parts of the Rotorua district, and the regional council and the kiwifruit industry were jointly-funding a control programme.

Mr Mather said kiwifruit seeds were often spread by birds, and possibly rats and possums.

"So it's important to give them little opportunity to snack on ripening fruit," he said.

Mr Mather asked farmers who feed reject fruit to stock to cover the piles with lengths of windbreak, a material that breathes and will not hasten fruit ripening.

It was best to feed out from the stockpile every day or two so large quantities were not left lying around.

Kiwifruit orchardists could also help by removing reject fruit from vines and mulching it as soon as possible, before it ripens and birds get to it. Once fruit was dropped between rows and mulched by a mower it quickly broke down into compost material.

- NZPA