Greenhouse insect import plan a big worry

Last updated 09:42 06/03/2014
White butterfly
HOT TOMATO: Importing parasites to kill white butterfly could cause irreversible effects to the environemment.

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A bug tomato growers want to introduce to control hothouse pests is a danger to New Zealand plants and insects, critics say.

Commercial fresh-tomato growers, Tomatoes NZ, want to introduce the bug to reduce their use of pesticides in hothouses, especially the white butterfly.

Tomatoes NZ asked the Environmental Protection Authority (ERA) in November to allow the insect macrolophus pygmaeus to be imported and released into greenhouses.

The ERA is now considering the request and submissions opposing the introduction of the bug.

The growers say it will feed on a wide range of greenhouse pests including whitefly, mites, thrips, aphids and leafroller, and say the bugs are considered effective as a bio-control in hothouses overseas.

The bugs, which have a particular fondness for white butterfly eggs, larvae, pupa and adults, also suck the juice out of plants as well as eating pests.

Growers are looking for more biological controls, as consumers demand lower pesticide use in commercial production worldwide, but still perfect-looking fruit. Pests are also developing resistance to insecticides.

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 about $120 million annually.

The growers' group said the insect would be critical for the long-term viability of the tomato sector, reducing reliance on chemicals with benefits for the environment, consumers and growers.

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

"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 Dr Margaret Stanley said.

"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."

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Stanley said the bug would have many opportunities to escape through open cooling vents.

It had become established outside greenhouses in Britain and the risk of the same thing happening here was high, she said.

Scientists at Landcare Research said they were also committed to biological controls, but concerns for New Zealand's unique native plants and insects saw them also oppose the application.

The Northland Regional Council also opposed the introduction of the bug, with the council's entomologist Dr Jenny Dymock saying the north might be particularly vulnerable to the insects establishing should they escape.

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

Woolley nightshade, another variety of the plant, was also found extensively throughout Northland and was a likely host, as were tamarillo, Dymock said.

Dr John Liddle for the Nursery and Garden Association, had no doubts the insects would escape into the wild as the climate warmed,and said wild insect populations would also spread. .

And while fewer white butterflies could be useful to their industry, Liddle said that overall there were too many unknowns about the bug's effects on native organisms and other exotic plants nurseries dealt with.

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

- Rodney Times


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