In the second week of September 2019 I took the long road across the Barrier Highway and out to South Australia for 12 days of African Boxthorn control on Boolcoomatta Station Reserve. This was my second visit and I was looking forward to re-acquainting myself with this mighty reserve and striking a blow for conservation.
Over the two weeks there was a total of nine volunteers who took part in the working bee. I knew that Kurt, the Reserve Manager would arrange a great works program and that he and my fellow volunteers would be great company. I was not disappointed.
The work was varied, with a focus on protecting the Oonartra Creek Flood-Out.
Protecting the Oonartra Creek Flood-Out
The Oonartra Creek Flood-Out is a central feature of Boolcoomatta. During major rain events the Oonartra Creek occasionally overtops its main channel and floods out onto the surrounding country.
As the water slows it drops its load of silt and vegetation debris, creating a fertile environment for a diversity of wildlife.
Our major task was to find and poison African Boxthorn (Lycium ferocissimum) plants that were infesting the Oonartra Creek Flood-Out, using a cut-stump method of applying the herbicide. We used a new gel herbicide preparation Vigilant II ®, a welcome ‘no-mess’ way of applying herbicide to cut stumps.
We found plenty of evidence of Boxthorn control already undertaken by previous working bees and by contract spraying. Some plants, however, had survived and needed to be re-treated. Kurt was busy answering calls of “Chainsaw here!” to cut through the larger thickets of boxthorn re-growth.
Kurt told us that from old aerial photos it was apparent that the Flood-Out once covered a greater area than it does today. Erosion gullies have developed along the eastern edge and these allow surface water to escape more quickly. With each flood event the gullies cut further upstream and thus reduce the area of the Flood-Out. In this way gully erosion reduces both the duration and area of flood events.
A major priority then is to stop further loss of the Flood-Out by preventing any extension of the erosion and restoring surface water flow. We spent a day or two on erosion works on the eastern edge of the Flood-Out.
We took standing dead scrub and laid it across the head of erosion gullies to provide a barrier to slow the flow of water and prevent the gullies from cutting back further into the Flood-Out.
We had some fun making wire and brush ‘sausages’ which were placed upstream of erosion gullies to catch debris over time and create barriers to the flow of water.
We also spent a day on the Eremophila Track removing an old fence-line. This part of the reserve was a contrast to the Flood-Out – it was open and rocky with spectacular outlooks. It was also very exposed and windy that day, but we all enjoyed the change of task and scenery. We removed nearly 2km of fence-line, restoring an unimpeded vista for anyone travelling that section of the track.
Visit by Troy Bowman from PIRSA
Towards the end of the working bee we had a special treat. Troy Bowman, from the Department of Primary Industries and Regional Development South Australia (PIRSA), spent an evening and next morning with us. In the evening, after a shared meal, Troy gave a presentation on the control of African Boxthorn and Opuntoid cacti in South Australia and an update on the status of biological control agents in South Australia.
Troy generously handed out a number of information booklets on weed management, which I think will be very useful. It was a great evening of information and discussion, topped off by a recital of our poetry tributes to Trevor the Racing Pigeon*!
The next morning Troy ran a field session for us, demonstraiting various control techniques for large woody weeds in a large stand of Peppercorn Trees (Schinus molle).
We had the opportunity to try out a capsule ‘gun’ for injecting herbicide capsules directly into the trunk of target trees (a variation of the drill and fill method). This technique has many advantages in terms of efficient use of herbicide and protection of off-target species, but it definitely takes some practice!
We also helped Troy and Kurt set up a small trial comparing the effects of different herbicides delivered by the capsule method.
Three chemical treatments were used:
Each treatment was applied to three trees each. The target trees were then marked by GPS for easy relocation.
It would be great to come back next year and compare the results for each treatment.
As always, Kurt was very generous in allowing us to explore the reserve in our time off. Being spring there were a number of plants in flower, especially in among the nooks and crannies of rocky outcrops.
Evenings were very busy and varied with sunset drinks, a walk to the shearers’ cave and seriously contested games of Scrabble and Rummikub.
Kurt kept us with a generous supply of eggs from his chooks - thanks girls.
Friday, on my last day, Boolcoomatta was engulfed in a large dust storm brought in by high winds. By the next day it was blue skies again as Elizabeth and I left Boolcoomatta for the long drive home.
I would like to thank Kurt for hosting such an interesting and worthwhile working bee. His planning preparation and thoughtfulness really made for a great experience. Thanks also to the other volunteers for your convivial company. I hope to meet you again on other Bush Heritage placements.
*Trevor was a racing pigeon who visited us for a few days before travelling on. One morning we saw feathers and thought he had been taken by a cat, but defying the odds he turned up the next day.