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17/9/2026
Grazon Extra the muscle for woody weed control
In a region of multiple weed species and challenging terrain Grazon Extra is the muscle herbicide for spray contractor Chris Callahan, of Colac in the western districts of Victoria.
Mr Callahan services an area from Geelong, west to Warrnambool and north to Ballarat with blackberries, ragwort, thistles and St John’s wort the main weed species.
“Blackberries are probably the worst,” Mr Callahan said. “Depending on how thick and how deep the blackberries are, you might only get to spray across 10 metres in that first year. When it dies and the canes drop a bit you can push in and get a bit further. It can take two or three years depending on how deep the infestation is.”
“Ragwort is another one and thistles drop thousands of seeds so if you don’t keep up and follow up you are in a bit of trouble.”
He said in the coastal areas, particularly around the Otway Ranges, the weeds were often in steep gullies so it was important to use the herbicide that was highly effective.
Harold Hanlon from Ag Warehouse and spray contractor Chris Callahan use Grazon Extra to control a range of weeds including blackberries, ragwort, thistles and St John’s wort.
“Product wise, we use Grazon Extra. We have for years – it is the muscle in the herbicide industry. Instead of going through and doing two or three visits to get complete control of the big weeds that we have around here, like Blackberry, ragwort and thistle, you can do one visit with Grazon Extra and it’s all done. We've been using Grazon Extra for a good while now and it’s a really good product.”
He said the best time to treat blackberry canes is between December and May when the weeds are actively growing.
“You can see that they're actively growing by the little tips. There's still a lighter green area, so they're still trying to invade the world. After application they are left for six months before being cut out or slashed. It gives that time to get the chemical back to the root base. There’s always a big seed bank as well with blackberries maturing and falling off.”
Mr Callahan said the weed size and infestation dictated the rates which might range between 350 and 500 mL per 100 litres of water.
Chris Callahan spraying blackberries with Grazon Extra in the western districts of Victoria.
“ Thistles are fairly easy to knock over. Mature blackberries and ragwort require a higher rate”
He said Grazon Extra worked well with a range of water types generally sourced on farm.
Quik Spray retractable hose units are used to attack the weeds and provide a reach of six to eight metres into the infestations.
“We thoroughly wet it to a point where it’s running off. That’s the secret. You need to get good coverage. “It’s an experience thing knowing how much water to put on to soak down and get underneath the leaves as well. You don’t want to waste chemical either, so you’ve got to be a bit smart about it.”
Mr Callahan said the effects of Grazon Extra were visual very quickly, which helped evaluate the job.
“You can spray today and tomorrow all those new soft tips will start to curl. “You've got an indication of what you’ve sprayed and what you haven't. After a week or 10 days it starts to go yellow.”
He said he kept using Grazon Extra because of its performance over many years.
“It’s the muscle product because it'll knock most things over and has a bit residual as well, which helps with the runners on the blackberries. Ragwort has a heap of little roots on it, and if you actually pull it out, or it gets knocked over, those little bits that are left will shoot again the next year. Grazon Extra stops that.”
Harold Hanlon, from Ag Warehouse, in Colac, supplies a range of products to Mr Callahan said blackberries were a major problem in the region.
“The birds pick the berries; it will go through their body and be dropped somewhere else. It’s a very invasive plant and so takes out a lot of productive areas.
“In addressing blackberries my go to is Grazon Extra. That is the number one product that I use because of the three actives that's actually in it. We have tremendous results.”
It’s very easy to pour and mixes really well with the appropriate wetting agents and, at the end of the day, we just get a really good result.”
