Eliora
The Department of Conservation tells us that New Zealand has been geographically separated from other land masses for over 8 million years. It is often said that New Zealand is dominated by birds, yet for every type of land bird in the country there are 200 kinds of insects, with a total estimate of about 20,000 insect species.
To a kiwi who spent years living out of New Zealand and a novice discerner of insects, it comes as a shock when you return home, to discover several unfamiliar bugs in the garden. When a new insect appears, it stands out. Like the COVID-19 virus, there is only one way they arrive here. Across our borders. By accident or intent.
Biosecurity is about keeping New Zealand free of unwanted pests and diseases. They focus on stopping them at the border or getting rid of the ones already here. New Zealand Biosecurity Border Control swung into action, when Queensland (Australian) fruit flies were detected in Auckland. This fly was identified as harmful to 80% of New Zealand’s multi- billion horticulture industry. They were trapped and successfully eradicated.
Put simply, the Queensland fruit fly spoils many horticultural crops, often making them inedible, according to the Ministry for Primary Industries (MPI)
– RNZ 2019
Care is taken, but New Zealand’s borders are porous. Passenger planes are no longer sprayed when people are still in the aircraft. There are many ports and 1000’s of containers unloaded each day. It is concerning to hear that some of these new insects which have crossed our porous borders, are out of control and are upsetting the ecosystem.
The Tasman District Council has had enough of one invader. Wasps! Kiwis agree wasp population has exploded in alarming numbers. It has been decided that the way to attack the huge number of wasps is to introduce two more insects to New Zealand. A hoover fly and a wasp nest beetle. They look mean and nasty.
Pest wasp species have been accidentally introduced to New Zealand. They are the Asian paper wasp, the Australian paper wasp and the German and common wasps. The German wasp was introduced with US aeroplane parts in the 1940s and the common wasp arrived only recently but is already widespread.
For decades New Zealand’s invasive wasps have had the run of the place, with no natural enemy to control the growing numbers. But that’s about to change, with the green light given today to introduce two insects from Europe to take on the pest. The Tasman District Council, which has a big wasp problem, applied for the bio control agents, a hover fly and wasp-nest beetle. The regulator, the Environmental Protection Authority assessed their safety.
“The reason why it’s safe is because these two insects only attack wasps and that’s been established both where they come from in Europe but also elsewhere,” said Chris Hill, general manager of hazardous substances and new organisms. Invasive German and common wasps, have overrun biodiversity in native forests and inflicted financial pain on farmers and beekeepers, costing them about $70 million a year. Beekeepers’ hives are often decimated by wasps.
“They’ll sit on the outside of the hive and work their way in, they will kill the larvae because they’re protein feeders and they’ll kill the bees, but then they also steal the nectar as well,” said Wendy Lane a beekeeper near Nelson.
“When the wasps arrived here, they found a wasp utopia, as it were they had no real natural enemies here. They left all their parasites behind, and they also found an abundance of honey dew,” said insect ecologist Richard Toft. But “wasp utopia” is in for a shock.
The hoverfly and beetle will both target wasp nests.
“The hoverfly manages to get in there and lay eggs in the nest and their larvae eats the wasps larvae, so if you get enough of these parasites in the wasp nest, they can have an impact on the population of wasps,” said Toft.
The Tasman District, with its honey dew covered beech trees, has the highest density of wasps nests in the world, with between 30 and 40 per hectare. The wasps have monopolised the honey dew, depriving other insects and animals of a food source, disrupting the ecosystem.
Wasp expert with Landcare Research, Bob Brown called the introduction of the new insects “monumental” for conservation. In the 1980s and 1990s, an attempt was made to suppress wasps numbers with the introduction of smaller wasps from Israel and North America but it didn’t work. The new beetle and hoverfly are expected to be effective, but the question is just how much?
“It’s not a silver bullet, but it’s one tool in the toolbox,” said Paul Sheldon, the Tasman District Council’s biosecurity and biodiversity co-ordinator.
tvnz.co.nz one-news, Cushla Norman 2021
Questions for an Entomologist
The Harlequin Ladybird was deliberately released in North America and Europe for the biological control of aphids. Its voracious appetite enables it to outcompete other ladybird species. They also eat Monarch caterpillars, so are often found on swan plants. It also contaminates tender fruit and grapes and leaves a distinctive taste, ruining wine. It is now regarded as a pest. When the hoover fly and wasp nest beetle’s food source of wasps is gone, what will become their next meal target?
Could this fly and beetle be regarded not as a ‘monumental’ good idea, but as pests themselves, introduced pests, in a few years time?
Other Pests, Some That Are Being Ignored by MPI.
Brown Stink Bugs
The brown marmorated stink bug could attack a wide range of New Zealand crops and infest local homes. Gardeners have been asked to be on the lookout because bugs that come through airports or seaports would attack their crops first.
Harlequin Ladybirds
Ladybirds are normally regarded as beneficial insects. However, the Harlequin Ladybird is regarded as a pest because they will bite humans and they may come indoors and emit a foul odour and cause stains. They also swarm and can be found in huge numbers inside a home. There is also concern that it may impact indigenous species of ladybirds, because its voracious appetite enables it to out-compete them.
Invasive ants
Most ants you will see in your garden are not a concern. However, we need to keep watch to ensure some species of invasive ants do not get established here. Early detection is important to the eradication and control of invasive ants.
Mosquitoes
New Zealand has 15 species of mosquito. Mosquitoes breed in standing water, so the best way to get rid of them is to remove things that hold water from your garden. Mosquitoes from overseas are a threat to our health, as many of them can carry dangerous diseases. There are 3 species of exotic mosquitoes that are asked to keep a close look out for – Asian, Malaria Mosquito, Southern Saltmarsh Mosquito.
Pea weevil
Pea weevils were found in April 2016 in the Wairarapa. New Zealand is confident that they have now been eradicated but, for assurance, monitoring of some commercial pea harvests will continue during the 2020 to 2021 season. Commercial and home gardeners are encouraged to stay alert for any sign of this destructive insect on their pea plants and pea straw.
Termites
Australian subterranean termites can cause structural damage to all types of wood, including timber house framing, furniture, fences, and trees. Occasionally these introduced termites are found in New Zealand and MPI is keen to identify any populations and eradicate them.
Hairy Caterpillar
The hairy caterpillar, called the Gum-leaf skeletoniser, was first discovered in New Zealand in 1992 and is now firmly established throughout the Auckland region. In 2007 three Auckland girls were stung in a tree by these venomous Australian caterpillars.
South African Praying Mantis
This mantis is predacious, kills NZ praying mantis, catches insects, and bites humans. It lacks the blue patch on front legs of the NZ smaller mantis, has a larger belly and goes up at the tail end.
If you see any of these insect pests, catch it and call the MPI Exotic Pest and Disease Hotline on 0800 80 99 66
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