Gorse is listed in the Weeds of National Significance. This is due to its invasive nature, potential to spread and economic and environmental impacts. On farms it reduces pasture production and thereby stocking rates, restricts access to water and land and provides food and shelter for feral animals. Fire hazard risk is also increased due to the inherent flammability of gorse. All of these aspects dramatically reduce property values.
A mature gorse infestation can annually produce 6 million seeds per hectare and seeds may remain viable in the soil for up to 30 years. Ensuring that existing plants do not produce seeds is therefore critical in the long-term battle to reclaim heavily infested areas.
Marcus Scott, field sales representative for Roberts Ltd in the Midlands of Tasmania, is very familiar with this problem. “There are still a lot of properties that won’t do anything about their weeds. I think there’s still hundreds of hectares through the Midlands here that could still do with treatment.” There’s no question that controlling gorse is a difficult and extended project, sometimes requiring three stages over subsequent years, as well as ongoing vigilance against any regrowth or new plants. “Some of these bushes are six to eight feet tall, so it’s a mechanical job upfront to get rid of all the big bushes and then treat the regrowth as it comes through. It’s a lot more cost effective that way” advised Marcus. However, the return on investment can take less than two years. “These areas could then be sown to improved pastures to dramatically increase the stocking rate through there. With the returns from Merino sheep at the moment, there’s probably no better time to get a good return to run more sheep.”
After many years of working in this area, Marcus only recommends one product, Grazon™ Extra herbicide from Corteva Agriscience™. Grazon Extra contains the powerful combination of triclopyr, picloram and aminopyralid. It can be applied by helicopter in Tasmania from summer to autumn. Developing a plan of attack will ensure best results. This should include identifying areas most at risk of infestation and areas subject to vermin and treating these first.
“Grazon Extra has certainly done a good eradication job on the properties that have used it. It’s one of these peace-of-mind products, you know when you sell it and give the right advice as what to apply it on, how to apply it and so on, getting the whole bush completely wet all over instead of just spraying parts of it, you know it’s going to work. It’s never been an issue in that regard”.
The active ingredients in Grazon Extra have plant hormone-like properties. They bind to protein receptor sites in the weed that normally regulate vital plant processes. Plant metabolism is disrupted and plant growth becomes deregulated. Symptoms may appear within hours to days, but full control takes several weeks to months, depending on environmental conditions. Symptoms include: thickened, curved and twisted stems and leaves; cupping and crinkling of leaves; narrow leaves with callus tissue; hardened growth on stems, stem cracking; enlarged roots and proliferated growth.
Marcus describes “there are areas where the use of Grazon Extra has been very visible, like along the Midland Highway, where it’s been used from a helicopter on some hills and they’re very visible from the highway. The coverage from the helicopter has been fine. You see the results a few months later and the hills have gone from being green, and yellow when the gorse is in flower, and after treatment it’s all brown. It’s done a fantastic job. These bushes have been there for years and you go down the highway a few months after they’ve been treated and all that yellow flower that’s normally there in spring and summer, and it’s all disappeared off the hills. It’s opened up a lot of grazing country and prevented further spread. The hills have regenerated with native pasture and sheep are grazing there now.”
When it comes to managing woody weeds, labour constitutes the greatest cost of the entire operation. Maximising the value of the cost of labour by using the best product the first time is critical to the success of the whole programme. “I know people have used other products in the past and tried to do a cheaper job and it hasn’t worked out. So they’ve effectively wasted money. And then they’ve used Grazon Extra. Grazon Extra has always been the trusted product. Everyone knows when you use it, and use the right wetter with it, you can usually guarantee that it’s going to work 100% of the time. That’s why it’s always been the go-to treatment for gorse” explained Marcus.
For more information on Grazon Extra, visit your local Roberts store.