The Harmless Kiwi Invaders

Living in New Zealand, we are constantly under threat of being invaded by insects from foreign countries. What we never give much thought to is whether or not OUR insects are invading someone else!

I decided to do some in-depth research (a quick 5 minute scroll on Google) to find out whether or not New Zealand is contributing to the worlds insect pest problem. Unfortunately, after all of my extensive research, the only invasive New Zealand pest I could find info on was a Mudsnail making a nuisance of itself in the U.S.A.

The lack of invasive New Zealand pests might reflect the characteristics of our fauna. Perhaps our insects are just too slow growing, wimpy and fussy to become serious pests in other countries.

 Anyway, I did find an example of N.Z insects in other countries.  They might not be pests, but stick insects are right up there with my favourites. As it turns out, Southern English gardeners have been blessed with the presence of stick insects for over 100 years now. This made me laugh, because I couldn’t find one for my insect collection to save myself!

There are currently three types of stick insect that have naturalised in England, having come from our shores. The Unarmed Stick Insect (right), the Prickly Stick Insect (left) and the Smooth Stick Insect have all made the long journey to the other side of the world, living in domestic gardens and nature reserves. They are not considered pests, and are thought to be examples of charismatic insects potentially worth protecting!

Stick Insects appear to have all the characteristics of a good pest. They reproduce parthenogenetically (meaning males are not needed to fertilise the females eggs), they feed on a wide range of plant species, nymphs grow quickly through to a mature stage, and colonies can be formed from just a single egg.

So, why aren’t these charismatic New Zealand stick insects causing our Pomey neighbours problems? Firstly, the stick insects do not respond well to colder conditions. Here in N.Z, they are not generally found below Nelson/Marlborough. In the U.K, stick insects mostly disappear over the colder months. Another reason for their lack of pestey status  is their relatively unaggressive feeding habits. They do not consume large amounts of foliage, and tend not to feed on fruits and other economic species. All things considered, our invasive stick insects are not considered to do any harm to the plants and wildlife of the U.K. I believe it is these types of characteristics that make New Zealand insects’ poor pests.

If anyone knows of invasive New Zealand pests in other countries, I would love to hear about them. Also, what do you think about my predictions on why New Zealand insects don’t make good pests?