Introducing Biological Controls
2023
When we heard that tradescantia biological controls were going really well in other parts of Aotearoa, but had not been successfully established in Taupō yet, we thought it sounded like a good learning opportunity!
The Brentwood Gully, where St Patrick’s School has a restoration project, has several patches of tradescantia that we had cleared with their students about 18 months ago to plant native plants. See the pictures below. Unfortunately, with the wet summer, it had come back in force, covering our native plants in a thick blanket.
A Year 6-7 class at St Patrick’s School Taupō agreed to take the project on. Our coordinator, Rachel, led a session with them to teach them about biological controls, how one living thing can be introduced to control another living thing. This video explains how that works, although it is American. (Are there any kids out there keen to make a video about biological controls in New Zealand?)
With advice and guidance from Waikato Regional Council, we headed into the gully with a group of students to pot up tradescantia plants and grow them. First we needed to speak to the owners of the neighbouring property about the project and get them on board. They were excited, as they have given up trying to control it. As this weed is so invasive, we had to get special permission from WRC to propagate these plants, and we had to make sure that we didn’t drop any pieces, or walk pieces out in our shoes. It can spread easily from a tiny piece, less than a centimeter long!
WRC had said that we could try establishing the fungal biocontrol and the tradescantia leaf beetle. These had been introduced to Taupō in the past, but there was no evidence to show that they had successfully established.
We contacted Enviroschools Waikato to find a school that had the beetles on their property. Maeroa Intermediate had lots of them in their gully and agreed to join us on this project. With their Enviroschools facilitator, the students designed and tested pooters to catch the beetles.
Instructions for making a pooter are here, you can watch a video here.
Our coordinator, Rachel, Adrienne from Enviroschools Waikato, and Hamish Hodgson from Waikato Regional Council all went bug hunting with the students in the Maeroa School Gully. They caught 200 beetles in 2 hours! There was lots of learning taking place in the trialing of different methods of catching beetles. We tried various nets, containers and even a tea strainer! The pooter was definitely the winner!
Rachel delivered these beetles to St Patrick’s School in Taupō and they went on a gully adventure with them. Before releasing them, they made sure to inspect their patch of tradescantia and mark out the edges of it (so that they can compare it later). They took before photos and checked that there were no signs of beetles already present. They chose a sunny spot to mark out a metre squared to be their spot to compare photos of later on. They also chose a control patch of tradescantia to observe too.
The beetles were released! It was very exciting to see them nibbling the leaves straight away.
The students kept some beetles in the classroom, so that they could observe them and breed some more. They were amazed at how quickly they decimated the plants that they had them on and they could see that even though they are tiny beetles, they eat a lot!
Waikato Enviroschools coordinators found some yellow spot fungus in Hamilton and another class at the school had a go at introducing that to the area with the Enviroschools coordinator.
Our team has had a lot of discussion around the cultural implications of introducing a species from one rohe to another. We realise, that when doing work like this, it is good to inform manawhenua and to ensure that a karakia is said to farewell and welcome the insects. This is an area that we will be working to improve our processes in with future biological control work. Our kairuruku reo Māori, Benoir, said a karakia and officially welcomed the last of the beetles into their new home in Taupō. It was a very special moment. Then we just had to wait until the summer to see if the beetles survived the cold winter here and established themselves in the area. Our fingers were crossed! (see the 2024 update below)
Thanks Waikato Regional Council for your support with planning this project, Waikato Enviroschools for joining us to make it happen, and Benoir for your advice and guidance from a cultural perspective. What an awesome collaborative project!
2024
We were very excited to find some beetles still alive at the start of 2024! We could only spot a few of them in the huge patch of tradescantia, but this was proof that they survived the cold Taupō winter! In February Rachel collected more beetles with Maeroa Intermediate. After the students had farewelled them from Kirikiriroa/Hamilton with a karakia, they headed to Taupō. St Patrick’s School students did a bug hunt and spotted 3 beetles on the tradescantia, then they released the next lot of beetles with a welcoming karakia. We’re hoping that they will establish a population that will help control the invasive weed that is smothering our native plants.