EPA is warned the release of bug to protect tomatoes could put native species at risk

New Zealand’s native insects and plants will be put at risk if a proposal to release a predatory bug to protect tomato plants goes ahead, says University of Auckland biosecurity lecturer Dr Margaret Stanley.

TomatoesNZ, the industry body which represents New Zealand tomato growers, has applied to the Government’s environmental regulator, the Environmental Protection Authority, to import and release Macrolophus pygmaeusas a biocontrol agent for the greenhouse whitefly. Growers say controlling greenhouse whitefly by introducing a biocontrol agent would lower the use of chemical sprays and increase yields.

But in her submission to the EPA, Dr Stanley says if Macrolophus pygmaeus is introduced to New Zealand, there is a high risk of damage to New Zealand’s unique flora and fauna.

“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.”

Dr Stanley says a number of aspects of TomatoesNZ’s application to the EPA are of concern, including the assertion that the predatory bug is a specialist whitefly predator.

“Given that it also feeds on aphids, moth eggs, caterpillars, thrips and spider mites this is clearly a generalist predator and the implications of releasing such an organism needs to be considered with great care. Best practice for biocontrol around the world is to use highly specific biocontrol agents to reduce risk.”

While tomato growers are seeking to breed colonies of Macrolophus pygmaeus for release into greenhouses, 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.

“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.”

Macrolophus pygmaeus was released illegally in New Zealand in 2007 but did not survive outside greenhouses. Dr Stanley says the industry is using that to support its case, but argues the bug was not released on a scale comparable to what is now proposed and the illegal release was also very localised.

“The illegal release in 2007 can’t be compared to what could happen under the new plan which will see the bug released into greenhouses on a much larger scale and over a far wider area,” Dr Stanley says.

Comparing New Zealand to the UK, where M. pygmaeus was introduced in 1991, was also misleading.

“Unlike Europe, a high proportion of our native invertebrates are found nowhere else in the world and some of them have yet to be scientifically described so that we don’t even know whether or not they are threatened or to what degree they will be impacted by the introduction of this new species,” Dr Stanley says.

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One response to this post.

  1. Nobody can quantify the magnitude of any risk posed by Macrolophus to the native environment, and I expect that any such risk is negligible. One of the main reasons why host specific biocontrol agents are preferred is so that they focus on the intended pest, rather than spreading themselves too thinly. Clearly, the pest must be the main target of the control agent! The danger of host specific agents is that they could shift focus to another species closely related to the intended pest, and this could be a vulnerable native species. This is why host range testing is done (note that it is done only on species closely related to the intended target pest). Macrolophus is a generalist with a strong preference for whitefly. It is therefore extremely unlikely to shift focus to a vulnerable native species unrelated to whitefly. In the absence of whitefly (unlikely in itself), it will most likely prey on whatever else is common in the same agricultural systems. It is perhaps unfair to compare Macrolophus to mustelids (stoats etc.) The latter were released into a relatively pristine N.Z., and shifted focus to vulnerable native birds. This could have been predicted (but wasn’t). A past mistake should not be allowed to hinder us today. I wish that this debate could have been conducted more objectively, and less emotively.

    Reply

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