Killing cactus at Goonderoo

Published 30 Oct 2017 
about  Goonderoo Reserve  
Marj Jones assesses a cactus.<br/> Marj Jones assesses a cactus.
Aerial view of Sword Cactus through the brigalow.<br/> Aerial view of Sword Cactus through the brigalow.
Dead sword pear in Zone C.<br/> Dead sword pear in Zone C.
A dead cactus that's wilted and completed brown. <br/> A dead cactus that's wilted and completed brown.
A sick Sword Cactus, which is still partially green. <br/> A sick Sword Cactus, which is still partially green.
A healthy Sword Cactus.  <br/> A healthy Sword Cactus.
Resprouting cactus.<br/> Resprouting cactus.

Volunteers play an important role in weed control projects across the country. On Goonderoo Reserve in Central Qld, the target species is Sword Cactus (Acanthocereus pentagonus) a tall, columnar cactus that reaches a height of 2–7 m.

Sword Cactus is multi-stemmed and highly spiky. It has the ability to form dense thickets and will dominate a vegetation community to the exclusion of many other plant and animal species. Thankfully, Sword Cactus has only been recorded at a handful of locations in Australia. One of these locations is the district of Fernlees, between Emerald and Springsure, which includes Goonderoo Reserve.

At Goonderoo, the infestation is threatening brigalow shrublands which are listed as threatened and, in 2016, staff conducted trials to determine the most economical and environmentally-friendly way to knock down this thorny invader.

Between May and September this year, volunteers continued this work and it’s clear that the efforts have paid off. In just over 12 months, what seemed like an insurmountable task has been reduced to a survey and hold operation. Towering tangles of cactus have been reduced to powder and, with follow-up on small and resprouting plants, we’re confident that this is a weed battle we can win.

Ecologist, Dr Rebecca Diete, recently visited Goonderoo to conduct a post-treatment survey and reported the following excellent results:

Post-treatment survey of sword cactus (Acanthocereus pentagonus) on Goonderoo Reserve  

Method 

A sample of 300 sword cactus plants was used to indicate weed control success on Goonderoo Reserve. For every plant located, a health score was assigned by visual assessment. Plants were classed as Dead, Sick or Healthy. Dead plants displayed no green colour and were usually considerably wilted in stature (Figure 1). Sick cacti were brown over the majority of the plant but still showed some signs of life. Healthy cacti were green over most of the plant. 

Results 

Of the 300 plants surveyed, 287 (95.7%) were either Dead or Sick (Figure 4; Table 1). The remaining 13 plants appeared healthy and were apparently missed by weed spraying activities.  

Number of Dead, Sick and Healthy sword cactus plants in each paddock sampled. 

Paddock name  Dead  Sick  Healthy  Total plants
observed
Gilgai 5 0 0 5
Springsure East 6 8 3 17
Springsure West  4 0 0 4
Indians West  0 19 6 25
Indians East  112 27 1 140
Chiefs  101 5 3 109
Percentage  76 19.7 4.3  

Conclusion

It's evident that the chemical treatment mix and application methods for treating sword cactus were very effective in treating the vast majority of these plants on Goonderoo Reserve. Follow up activities should include treating the small number of plants missed by the initial treatments, spraying of newly generated plants and ensuring that all sick cacti are dead following a long enough post-treatment period.

In 2018, we will continue working with neighbours and the local Council to and eradicate Sword cactus from the brigalow stands at Fernlees enhance environmental values at the landscape scale.

Aerial view of Sword Cactus through the brigalow.<br/> Aerial view of Sword Cactus through the brigalow.
Dead sword pear in Zone C.<br/> Dead sword pear in Zone C.
A dead cactus that's wilted and completed brown. <br/> A dead cactus that's wilted and completed brown.
A sick Sword Cactus, which is still partially green. <br/> A sick Sword Cactus, which is still partially green.
A healthy Sword Cactus.  <br/> A healthy Sword Cactus.
Resprouting cactus.<br/> Resprouting cactus.