HSIE K–12

WARNING – Aboriginal and Torres Strait Islander viewers are warned that the following video may contain images and voices of deceased persons.

[Screen reads – Focus question: How can Cat’s claw creeper be prevented from causing long term ecological damage in the upper Clarence River Catchment]

Narrator

Cat's Claw Creeper has become a major problem in Australia and there has been extensive research to how to prevent it from causing long-term ecological damage. Control methods today include biological control, physical weed removal, chemical control, mechanical control, foliar spray and cut stump application. Local Landcare and tourist operators at Tabulam incorporate environmental weed education as a part of their programmes of environmental restoration. We talked to Terry Moody, an experienced weed control expert about the issues surrounding the spread and control of Cat's Claw Creeper.

Terry Moody – CEO and weed expert, Upper Clarence combined Landcare

The big issue, how do we do anything about it? It's easy to kill, well comparatively easy. If you've got small vines like the one I had here before that was sticking to me, it's simply a matter of cutting them off, bending them over and dipping them into some herbicide so they suck it up and they die.

The bigger vines, something that big, you've actually gotta cut it off with a chainsaw and you paint the herbicide on top. The challenge is getting enough herbicide in to kill those underground tubers and there's so many of them. So the smaller the vine is, believe it or not, the harder it is to kill, the easier it is to treat, but the harder it is to kill because you've only got a very small surface area for the poison to go into those, sometimes tubers almost as big as your head. So it becomes an issue in terms of having to go back and back and back again.

On top of that, there's a huge seed bank and the seed seems to last about three years in the soil. When we first started doing work with our crew, we were told it would only be 18 months to two years. It appears to last a lot longer than that. So you can go in and you kill the big vines, particularly if it's somewhere with light, you can come back sometimes six months later and the ground is covered with new ones coming up. It might only be that high, but you dig them out and they've got a tuber on the bottom the size of a 20 cent piece, even when it's only that high with two leaves on it. So you can imagine the mass that's under the ground when you've got vines this size.

So really, it's a question of being strategic, looking at where you can control Cat's Claw. On a landscape scale, start at the top end and work your way through. On a localised scale, you pick the areas where you've got something that's really good conditions. So you've got bushland that is really top quality, has a lot of habitat value, has a lot of aesthetic value, it's really nice to look at and you might say, well we really need to make a concerted effort here to keep that value that's already there.

In some other areas, you might just have to let it go with the limited resources that we have. So it's a combination for us, at looking at a catchment, trying to work from the top all the way down because those seeds blow up and down, but the tubers get washed primarily down. And then picking individual sites themselves for their own special values. And that's the way we do it. We found that in general, you have to do about five years worth of follow-up work to actually win and say you're winning, but it could be up as far as 10 before you won't have any vines coming up.

I didn't mention previously the growth rate of some of these things, so we've actually killed Cat's Claw in some areas and gone back three months later and there have been new vines that have sprouted on the ground and grown two metres up the tree. In three months!

Narrator

An alternative method to controlling weeds is through biological controls. Biological control involves the use of insects or pathogens that affect the health of the weed. Usually these bio-control agents are from the same country of its origin as the weed species. Biological controls are released as strategic infestation sites and then spread naturally to the other infestations of their host weed.

Managers have trialled biological control in the Upper Clarence catchment. Two insects, the Tingid Bug and the Leaf-Tying Moth have previously been released. Also, field releases of Leaf Mining Jewel Beetle commenced in September 2012. We talked to Terry about his knowledge and experience of using biological controls. It is really interesting to hear the issues of frost and how it has affected the success of biological controls.

Terry

Cat's Claw having come from a tropical area has tropical pests associated with it such as insects that eat its leaves and maybe even mildews and moulds and all sorts of things that keep it under control in those areas. So it doesn't go as rampant as it does here. So when we take a plant and take it from an area where those things exist and bring it here, and we don't bring those pests with it, then that encourages it or allows it to get away and grow a lot faster.

So in an effort to try and control some of our major weeds including Cat's Claw, there's been a lot of work done on biocontrol, so the classic one that everybody talks about is Prickly Pear. There was a release of a biocontrol agent for Prickly Pear and it's now essentially under control and it's always a delicate balance. So if you wipe out the Prickly Pear, then there won't be enough Prickly Pear for the biocontrol to survive. So then if the Prickly Pear comes back again, you won't have anything to control it. So it's a tricky thing, but biocontrol doesn't result in complete removal, but it helps to get it down to a stage where you can properly progress with it.

And that's part of our aim in Landcare, is actually to go onto people's properties, help them deal with an issue that's been allowed to grow, in some cases for over 100 years, and bring it back to a scale where they can take over when we finish and they can continue to progress it.

So if we talk about biocontrol for Cat's Claw, a few things have been introduced. There was a Tingid Beetle from South America, more recently a Jewel Beetle. If you think about it, it all makes sense except for one thing. The reason that Cat's Claw, the place that Cat's Claw is out here on the riparian areas is also now because we've cleared so much country around it, an area that's subject to very heavy frosting, particularly if you're coming away from the coast.

So you take these biocontrols, the Tingid Beetle or the Jewel Beetle and you put them out into these areas, in the riparian areas and they might do a good job for the first spring and summer, and then as soon as the first couple of frosts come, all the biocontrols die out. So the Cat's Claw is already established. It's well and truly secure, but the biocontrols die out. So unfortunately we've had no real success with any biocontrols on Cat's Claw away from the very coastal areas where they don't have frosts. But they're still continuing to trial various things, look at different insects, but it's a difficult thing when you've got a plant now growing in an environment which differed so much from where it was before and had its natural biocontrols with it.

Melissa

How have you treated Cat's Claw on your own property?

Steve Ross – Tourism provider, owner of Clarence River wilderness lodge

Where we are, the Cat's Claw is only in small amounts, so it's actually, you can achieve something with it. From various grants we got through the Upper Clarence Combined Landcare, we've been able to attack the isolated vines that are in the area.

Narrator

As Terry explains, biological control agents can reduce the vigour, size and competitiveness of the weed infestations, however, they rarely get rid of the weed altogether. They also have their limitations and do not work in all situations. In this case, Terry shares how the insects would die due to the low subzero temperatures of frosts. So insects introduced as biological controls may not survive in places where the environment and climate is different from the one they evolved in. For this and other reasons, biological controls work best in conjunction with other control methods.

[Screen shows images of, physical weed removal, chemical control, mechanical control, foliar spray and cut stump application]

List of sources and acknowledgements:

1. Video – Drone footage of The Everlasting Swamp. We would like to thank The Everlasting Swamp National Park and Jessica Robertson Photography and Design for contributing their beautiful drone footage

2. Narration – Voice over by Melissa Ellis, Southern Cross School of Distance Education
   
3. Acknowledgment – We wish to thank Father Pop Harry Walker, Annabelle Walker, Roy Bell, Jubullum Local Aboriginal Land Council, Steve Walker, Marty Walker, David Foley, Upper Clarence River Landcare, Terry Moody, Steven Ross, Frederick Ellis
   

[End of transcript]