Insect import plan a big worry

21:00, Mar 05 2014
White butterfly
HOT TOMATO: Importing parasites to kill white butterfly could cause irreversible effects to the environemment.

It's tricky business trying to be environmentally friendly and striving for sustainability.

Efforts by commercial fresh tomato growers Tomatoes NZ to introduce a bug they hope will reduce their use of pesticides in New Zealand hot houses, especially against that bane of all gardeners, the white butterfly, have hit some strong opposition. 

The group applied to the Environmental Protection Authority in November last year to allow the insect Macrolophus pygmaeus, to be imported and released into green houses. 

There the growers say they can feed on a wide range of greenhouse pests including whitefly, mites, thrips, aphids and leafroller.

They are considered effective as a bio-control in hot houses overseas.

The bugs are ''meat and veg'' critters and suck the juice out of plants as well as eating pests.

And they have a particular fondness for white butterfly, be they eggs, larvae, pupa or adults. 

With consumers calling for lower pesticide use in commercial production worldwide, but still perfect looking fruit, along with pests growing resistance to insecticides, biological controls are being looked at more.

There are about 150 growers in New Zealand who export 40,000 tonnes of fresh fruit mainly to Australia with most grown year round in greenhouses.

The industry is worth around $120 million annually.

The growers group says the insect will be critical for the long-term viability of the tomato sector, reducing reliance on agrichemicals with benefits for the environment, consumers and growers.

While the growers' efforts to reduce agrichemicals have been praised by many of those opposing their application, the risks to native insects and plants should they escape is too great they say.

''The most reliable climate modelling shows Macrolophus pygmaeus would have optimal ecoclimate conditions to establish in Northland, Auckland and the east coast of the North Island, and suitable conditions extend south to Nelson,''  University of Auckland biosecurity lecturer Margaret Stanley says.

''There is a risk some New Zealand native species will be lost if this application is approved or at the very least there will be irreversible damage to plant and invertebrate animal communities. While the industry's drive to reduce the use of chemical sprays is admirable, the likely negative consequences for New Zealand are likely to be worse than the current spray regime,'' she says. 

Dr Stanley says the bug will have many opportunities to escape through open cooling vents.

It has established outside greenhouses in the UK and the risk of the same thing happening here is high, she says.

While scientists at Landcare Research say they are also committed to biological controls, concerns for New Zealand's unique native plants and insects has also seen them opposing the application as does the Northland Regional Council.

The north may be particularly vulnerable to the insects establishing should they escape, council entomologist Jenny Dymock says. 

As well as the north being warmer, which suits the insects, they are known to live on black nightshade commonly found outside greenhouses here, she says. 

Another variety of the plant woolley nightshade is also found extensively throughout Northland, and is a likely host as are tamarillo, says Dr Dymock.

As the climate warms with climate change the wild insect populations will also spread says John Liddle for the Nursery and Garden Association, who has no doubts the insects will escape into the wild. 

And while fewer white butterflies could be useful to their industry, Dr Liddle says overall there are too many unknowns about the effects on both native organisms and other exotics plants nurseries deal with.

The EPA is currently assessing submissions to decide if the benefits of Macrolophus being available to NZ growers will outweigh any risks. 


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