Herbicide: Spray & Injection

Herbicide Spray: Mature Plants

In 2004, students completed a project titled “Spray application of Glyphosate Trials Nuggetty Hills – Victoria” as part of the Diploma in Conservation and Land Management at Bendigo Regional Institute of TAFE. The aim of the 2 year project was to examine the efficacy of surface spray of 2% glyphosate and 0.2% Pulse on wheel cactus (Opuntia robusta). Overall, the results demonstrated that  a 2% glyphosate spray application significantly reduced the development and spread of wheel cactus. However, after 2 years regrowth was evident indicating that follow up control methods are required with this approach. This method is useful for preventing fruiting (and therefore viable seed production) and to damage large plants so access is gained to dense stands to enable further control measures. Click on the file name here to view the project report: Baig Tyler spray trials

Glyphosate Spray: Immature Plants 2013

Trials will be conducted with sprays of immature plants with different concentrations of glyphosate. The first trial using a spray with 1% concentration of glyphosate was completed at the end of July.  A marked plot of immature plants (new recruits) were saturated with the spray at sunset and then followed up every 4 weeks for 3 months to assess damage and kill rates. The results were not so promising with only 20% of plants showing any damage after 3 months. The results can be viewed in this Field Trial Sheet TCCG Glyphosate spray trial record sheet 2013. This trial will be followed up with another using a stronger dose of glyphosate and a wetting agent on immature plants.

Glyphosate and Synertrol Spray Trials: Immature Plants 2014

A second trial commenced on 3rd March 2014. Three plots of 20 immature wheel cacti were sprayed with different doses of glyphosate in the form of Wipe-Out 450  (450 gram glyphosate per litre) mixed with Synertrol Horti Oil (905gm per litre emulsifiable botanical oil mixed at the rate of 10ml per 3 litres).  Site 1 was sprayed with 1% glyphosate, Site 2 with 2.5% and Site 3 with 5%.  The results have been followed up monthly  over a 6 month period and at the end of this time 35% of young wheel cactus were damaged/dying in Site 1 and the remainder dead. In Site 2 25% of the plants were dying and 75% dead, whereas in Site 3 only one plant was still alive and it was dying. There was no regrowth from dead plants in any of the sites. The Field Trial Record Sheets with the 6 month results are available here:  Glyphosate-synertrol spray site 1 Glyphosate-synertrol spray site 2 Glyphosate-synertrol spray site 3

Herbicide (Glyphosate) Injection Technique

The injection technique consists of injecting ALL outer wheels (pads/lobes) of the plant and the second in if possible. The injector is inserted into the side and deep into the wheel and then pulled out slightly before delivering the dose (to prevent splash back). The concentration of glyphosate is 33.5% and each outer wheel (pad) is injected with 4ml, less if it is a very small wheel (pad). It is important to inject all outer wheels (pads). If one is left then it will drop off the dying plant, take root and grow into a new plant. Once a plant has been injected it is sprayed with a dot of highly visible paint to alert others that it has been treated.

The best way to inject

It is very important to inject the wheels correctly. Make sure you insert the injector into the side of wheel/pad and insert across the centre before pulling back a little to deliver the dose (insert and remove a little). if you stab the wheel and inject you will be trying to force the herbicide in and it can gush out as the injector is removed. With stabbing the herbicide also dribbles out of the stab wound and the plant then heals itself around the wound. The following slide show illustrates incorrect injecting – that is, stabbing rather than true injection and no effect on the plant 2 months later.

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