Finding new ways to knock Neem
Controlling woody weeds like neem (Azadirachta indica) means long sweaty days for teams in the field, carrying litres of herbicides, fuel, solvents and water, and using and maintaining heavy, sharp equipment. One of the common and most effective methods for controlling neem is spraying around the base of the trunk with a mix of herbicide and a solvent (often diesel fuel). The solvent helps the herbicide to penetrate the live tissues of the tree, which typically dies within a couple of months. Another method is to cut the tree down using a chainsaw (or, if it is small enough, loppers) and quickly paint the cut with a herbicide mix. While these methods can be effective, they pose some environmental, health and safety risks. Because the mixtures are liquid, it is easy for people doing the work to be exposed to herbicides directly (on their skin or clothing) or indirectly (in the air). Additionally, the use of liquid herbicides increases the likelihood of native plants and insects being accidentally poisoned.
What we have done
In 2018/19 we trialled a new ‘drill and pill’ method for controlling neem. With the support of Nyamba Buru Yawuru, Yawuru Country Managers, Department of Biodiversity Conservation and Attractions (DBCA), DBCA Yawuru rangers and community members, we have investigated the effectiveness and benefits of capsule technology to deliver dry herbicides into weed-trees with minimum fuss.
Developed by Bio-herbicides Australia, the capsules contain herbicides commonly used to target woody weeds, but in a dry form. The capsule is inserted into a small hole drilled into the side of the woody weed (such as neem). The hole is then sealed airtight with a small wooden bung. The tree sap dissolves the gel capsule, allowing the herbicide to be directly absorbed into the tree’s tissues.
This technique has a number of advantages over traditional methods. It is easier and safer to use, requiring only a cordless drill, a pair of gloves, a container of herbicide capsules and a container of bungs. Weed controllers operate in an environment with fewer risks, as there is no direct application of solvent, less herbicide is used, and dry herbicides are less likely to make direct or indirect contact with the operators or the environment.
Our pilot study on neem control, conducted at Coconut Wells north of Broome, compared traditional methods of woody-weed control (spraying, cut and paste, basal bark) with the new drill and pill methodology. The field trial report concluded that the new method is very effective in killing neem. It acts quickly, has a moderate cost, comes with lower occupational health and safety risk, and there is less opportunity for it to be spread more broadly in the environment.
At this stage, ‘drill and pill’ is a promising new weeding technology to be used in conjunction with other methods: handpulling of seedlings, basal barking, and cut and paste. Although only trialled on neem, it has some potential to be used successfully on other large woody weeds such as Parkinsonia aculeata, Leucaena leucocephala or Mimosa pigra.
KNP has also worked with groups including Bardi Jawi Rangers, Nyul Nyul Rangers and Nyikina Mangala Rangers to provide an introduction and instructions on the use of the ‘drill and pill’ methodology.
With the help of Nyul Nyul Rangers we have produced an instructional video:
We have also developed a drill and pill weeding guide, with a summary of the results of our trial.
Into the Future
The herbicide capsules are still only available on a trial basis while the product is being approved for market. We are able to provide advice to people wishing to access and use the capsules under their own trial agreement.
KNP will continue to work with others to build skills and share knowledge through the Kimberley Weed Network, the Kimberley Weed Forum 2020 and other groups.
The trial was carried out with support from Nyamba Buru Yawuru, Yawuru Country Managers, Department of Biodiversity Conservation and Attractions (DBCA), DBCA Yawuru Rangers, and Jeffery and Donna Foy.
We thank John Szymanski, Dick Pasfield, Allen Wedderburn, members of the Society for Kimberley Indigenous Plants and Animals, and staff from North Regional TAFE for their valuable advice.
Herbicide capsules and project support was provided by BioHerbicides Australia under a ‘Permit to allow the conduct of small-scale trials with Agvet Chemicals’ Number: PER 7250.
Yawuru, DBCA, parks and wildlife, Nyul Nyul Rangers, KLC, SKIPA,
We are grateful for support of the Western Australian Government NRM Program.
Links to interviews and media
For more information contact:
Louise Beames [email protected]