Herbicide gel for woody weed control

Spraying with herbicides can be a risky activity, especially in ecologically sensitive areas. Problems can include chemical runoff and residue build up in the soil.

However, a practical solution may be at hand - a low toxicity, herbicide gel has been developed that can be applied directly onto the cut stem of the weed without harming adjacent plants or pasture.

Some years ago, HortResearch scientists Brian Ward and Ron Henzell recognised that effective woody weed control was a problem and began investigating alternative control options. They formulated and trialled a range of herbicide active ingredients in gel formulations, which adhere to cut stems better than traditional liquid herbicides. Different application methods were also trialled as it was recognised that to solve the problem, the application method, in combination with the gel, was going to be a key to success.

The result of this research work was the development of a low toxicity herbicide gel containing only 5% picloram as the active ingredient. The gel has the safest herbicide classification and falls into the same category as many organic or biological products.

The gel can be either applied by cutting the plant with a pruning saw or loppers and then directly squeezing the gel on to the cut stem from a brush bottle, or by means of the TIPIT™ gel pruner which allows simultaneous application on stems less than 15mm diameter.

The gel is absorbed directly into the plant and, provided it is applied carefully, there is no runoff and no soil or adjacent plant contamination. The best results are achieved by applying a 5 millimetre thick layer of the gel over the entire cut stem.

As an indication, about 2 grams of gel are normally applied onto a 25 mm cut stem. Therefore, the 240 gram brush bottle can treat 120 stems of 25 mm diameter.

Advantages of Vigilant® herbicide gel

  • Less herbicide needed (than for spraying)
  • Lower concentration of active ingredient
  • No measuring or mixing required
  • Easy application
  • No spray drift
  • Minimal risk to non-target plants.

Vigilant® is effective (100% kill) in controlling:

  • Old man’s beard
  • Climbing spindleberry
  • Japanese honeysuckle
  • Grey willow 

Interim trial results suggest that close to 100% kill can also be obtained on:

  • Cotoneaster
  • Darwin’s barberry
  • Elaeagnus
  • Kahili ginger
  • Tree privet
  • Chinese privet
  • Gorse
  • Wandering willie
  • Agapanthus

Although the gel penetration can take slightly longer in the southern or colder regions of New Zealand (1-2 days compared with 2-4 hours), good efficacy was achieved throughout the year. Successful control was even obtained when the gel was applied in light drizzle, although it is recommended to use the gel in fine weather.


Open SpaceTM Magazine No. 49, October 2000 © QEII National Trust


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