How To Host A Vegetarian Invader

Posted by Jessica Devitt @Colette_Keeha

Recently I just said goodbye to roughly 200 guests. They were not thankful for the hospitality I showed them, they sometimes disliked the meals I served, so much so that they would rather starve than eat, and when I showed them to their new living quarters they would vomit on me to show their disapproval. I still really liked them though. My guests were most probably from Australia, but their descendents are all over the world. Their full name is quite a mouthful, Henosepilachna vigintioctopunctata, but we are on a first name basis now, so I go with the more common ‘hadda’ beetle.

From left:  Enjoying an early lunch of poroporo, hanging together in pyjamas, and baby-sitting

From left: Enjoying an early lunch of poroporo, hanging together in pyjamas, and baby-sitting

The hadda beetle was first discovered in Auckland, New Zealand in 2010 and is a well known pest of a large range of crop species, like potatoes and tomatoes from the Solanaceae family. As part of my MSc, I’ve host-tested the beetles on some native New Zealand Solanaceous plants, like poroporo (Solanum aviculare). Many native New Zealand plants are in decline, and native Solanaceous plants, like poroporo, are important food sources for our fruit-eating bird species. Adding more pressures, like a Solanaceae-munching hadda beetle, could push them further into decline.

To test the beetle’s host range, I did a series of experiments that could not only tell us if the beetle would eat the plants, but more importantly, if the beetle could maintain a self-sustaining population on our native plants. I used the ‘no-choice’ host-testing method, where the beetle is confined to one type of plant and the ‘multi-choice’ test, which allowed the beetles to ‘choose’ to eat or oviposit on a plant from a range choices. Early results show that hadda beetles are indeed happy to munch away and lay eggs on NZ’s native solanums. But to what effect on our plant populations? Watch this space…..

jess Jessica Devitt is a MSc student at the Centre for Biodiversity & Biosecurity, School of Biological Sciences, University of Auckland. She is researching the potential host-range of the hadda beetle in Auckland to assess how it might impact on native ecology. She is supervised by Margaret Stanley

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