Speaking as the international guest at the Foundation for Arable Research (FAR) annual crops expo, Boutsalis said herbicide resistance has been a challenge for Australian croppers far longer than it’s been a nuisance in NZ.
“In Australia no farmers have stopped farming because they have got herbicide resistance. But it is a lot more challenging.
“Australia is ahead of NZ, way ahead, but it’s not a failure to have herbicide resistance.
“In NZ we believe there is a lot less herbicide resistance than in Australia and that comes back a lot to the different ways of farming.”
Resistance in Australia has been dominated by continuous cropping, single crops per year and over-use of herbicides, especially in the 1980s and 1990s.
“Over-reliance back then on a narrow range of herbicides resulted in the initiation of the widespread resistance occurring in Australia today.
“Cross-resistance is also becoming problematic and herbicides do remain the main method of weed control but other methods are being incorporated into farm systems.”
Australian growers, with fewer crop rotations, reduce their range of tactics for annual ryegrass, the main weed.
In recent years researchers have been doing random weed surveys and are finding resistance is plateauing, even going down in some cases.
“We have researched over 20 million hectares of cropping over a five-year period. We conduct seed testing the next year and what we are doing is confirming resistance.
“Farmers are doing a really good job and controlling weeds even though they have got herbicide resistance. They are using different chemistries and different modes of action, other herbicides and options for control.
“It’s not a sealed bullet. There are a lot of tactics.”
Boutsalis said the industry has invested hundreds of thousands of dollars in the surveys and that has raised awareness with the chemical companies and they have responded by investing and producing new modes of herbicides to help growers tackle the multiple-resistance weeds that exist today.
Over the past five years several new modes of action herbicides have come on the market and there’s more to come.
“We expect by 2020 we will have three new modes of herbicides to control ryegrass in a cereal crop.”
FAR is planning to introduce random weed surveys in NZ to get a more accurate picture of the resistance gaps between the two countries and help find which herbicides are failing in NZ.
Boutsalis encouraged Kiwi croppers to follow the lessons learned by their Australian counterparts and use multiple tactics including herbicides with different modes of action than in-crop herbicides.
The change from full-cut cultivation to minimum tillage over the past 20-odd years has altered weed seed distribution to the top few centimetres, improving effectiveness of pre-emergence herbicides.
“The availability of a large pool of diverse herbicides should reduce the risk of resistance developing to any particular herbicide.”
While Australia now has more than 500 glyphosates available, NZ has about 100.
Using herbicides correctly is key to success.
“Testing of a few glyphosate products has shown vast differences in activity between the species with some effective on glyphosate resistant ryegrass if applied at young growth stages.”
Boutsalis urged farmers not to spare expense.
Products from more reputable companies will generally be made with higher quality components.
“While they will be more expensive they generally will work whereas cheap glyphosates made with really cheap components just don’t work.”
Good water quality also increases the effectiveness of the application because dirty water tends to bind the glyphosates and reduce effectiveness.
“Generally, herbicides from reputable companies that offer a quality guarantee are more effective over a wide range of environmental conditions.”
Farmers in Australia using top label rates and managing application to get optimum effectiveness are getting the best results, Boutsalis said.
