Safer use of herbicides for tree control

Nov. 2, 2023 | 5 Min read
There is a new, innovative and scientifically driven method for dealing with unwanted trees and woody weeds, thanks to a unique herbicide delivery system developed by the University of Queensland (UQ) and Bioherbicides Australia (BHA).

There is a new, innovative and scientifically driven method for dealing with unwanted trees and woody weeds, thanks to a unique herbicide delivery system developed by the University of Queensland (UQ) and Bioherbicides Australia (BHA).

A collaboration between UQ and BHA has seen the development of an herbicide-filled capsule that is implanted directly into the stem of the target tree.

Bioherbicides Australia MD Peter Riikonen says this method of weed control is practical, portable, and far more convenient than other approaches.

“It has the added benefit of greatly reducing, if not eliminating safety risks to workers and harm to the surrounding landscape,” he said.

Currently there are various strategies for herbicide-based control of undesirable trees.

These methods include foliar spraying (where the herbicide is often diluted in a water before spraying), basal bark application (where the base of target tree is heavily sprayed with a mixture of herbicide and diesel distillate), and the cut stump method (where the tree is felled before painting or spraying the cut surface of the stump with a herbicide solution).


Manual Drill and Fill (Stem Injection).

There are also ‘drill and fill’ approaches where holes are manually drilled into the trunk and liquid herbicide poured into these holes.

Mr Riikonen said these strategies have limitations in their ability to control woody weeds effectively.

“For example, the efficiency of spraying is affected by environmental factors such as wind, temperature, and humidity. The use of sprayer applied herbicides is restricted by the closeness of the unwanted trees to sensitive waterways, crop and pastures.

“Furthermore, there are legislative and environmental concerns regarding contamination of soil and harm to adjacent wanted trees when using traditional methods of weed control.”

Mr Riikonen said having a new technologically driven system that addresses many practical and environmental concerns regarding control of unwanted invasive trees is a game changer, especially as there have been few advances to date.

“This ingenious UQ/BHA technology uses herbicide-filled capsules implanted directly into the stems of invasive woody weeds.

“To facilitate the delivery of the capsule into the tree, an easy-to-use applicator – the Injecta - has been developed. The Injecta is designed to drill a hole into the trunk, insert the herbicide capsule and a sealing plug.”

The sealing of the capsule ensures that moisture is retained, and oxidation of the hole is prevented allowing the capsule and herbicide to dissolve, allowing rapid uptake into the tree’s vascular system.

The Di-Bak G (glyphosate) and Di-Bak AM (aminopyralid/metsulfuron) range of products. 

The capsule and plug can also be manually and simply inserted into the tree using a standard cordless drill.

Professor Victor Galea from UQ said the process of implanting dissolvable capsules bypasses the need to wastefully apply herbicide sprays over large areas. Due to the small amount of herbicide in each capsule, and the targeted application there is minimal loss.

“Another reason why this delivery system is so useful is that it protects non-target plants, which are often damaged through unintentional contact when using traditional methods such as spraying,” Professor Galea said.

This application method significantly reduces environmental and operator exposure to herbicide and reduces waste as unused capsules can be stored for long periods. The method also is not subject to external environmental conditions as capsule insertion can be undertaken, for example, under windy conditions or near waterways.

Mr Riikonen said the portability and convenience of the system, coupled with its proven efficacy and safety, mean the encapsulated herbicide could be used in a variety of settings and locations and could revolutionise the way agricultural and environmental managers battle invasive weeds.

Two products, Di-Bak G (glyphosate) and Di-Bak AM (aminopyralid/metsulfuron), are currently available in Australia along with the Injecta applicator and can be purchased through agricultural supplies outlets across the country as well as directly from BHA.

BHA is continuing the product development and expanding this proprietary delivery system to plant protection field. In the pipeline are capsule products to control unwanted insects and fungi in crop trees and other valuable trees.

Mr Riikonen said these new products and application method will bring along significant savings in materials and operational efforts.

“There is a great potential for this new technology to change the way we manage invasive pests and improve worker and environmental safety by applying chemicals in a more targeted and controlled way.”

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