Pre-emergent herbicides vital for weed control - Elders Rural Services
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Pre-emergent herbicides vital for weed control

Pre-emergent herbicides have been vital in the fight to control problem weeds for Terry Edis of Elders, Ariah Park, in southern New South Wales.

Mr Edis explains that the region is a mixed farming area with livestock favoured and cropping systems made up predominately of barley, wheat and canola, and legumes when needed.

There are a wide range of weed species challenging farmers through the district.

“Our prominent weeds are ryegrass, black oats, cape weed, wireweed and fumitory,” Mr Edis said.

“In wet years we’re getting a lot of toad rush, milk thistles, prickly lettuces, fleabane and a lot of radish,”

It’s a numbers game. Our pre-emergents are absolutely critical to our cropping system. The post-emergent situation is not great, and probably getting worse by the year, so we really need to manage the numbers of weeds, and hope that our pre-emergents do a really good job to get us through.

He said the reliance on pre-emergent chemistry over the years has caused some issues with weed resistance and it is something he was looking at in detail to determine what options to use in different paddocks.

Group 1 (formerly A) and Group 2 (formerly B) ryegrass resistance is common in the area, but they are also looking at resistance in black oats.

“We’ve got to do a lot more resistance testing this year,” Mr Edis said.

“We’re pretty certain we know where resistance is with annual ryegrass, but black oats have really stood out for us this year. I think having a longer wet season, a few weeds that might otherwise have struggled are really showing their heads.”

One of the pre-emergent options trialled this season was Overwatch® Herbicide, from FMC, which is registered for use on wheat, barley and canola.

Overwatch® Herbicide is a Group 13 herbicide (formerly Group Q) so a different mode of action to other pre-emergent herbicides being used in the area.

“I saw Overwatch® Herbicide at the trial sites at Temora and definitely wanted to have a have a look at it to see how it went in our systems,” Mr Edis said.

“We had it across all the registered crops – wheat, barley and canola. I didn’t get people to use it in their whole programme but rather get a feel for what sort of results we could expect.”

“I think we’ve seen quite a good amount of residual activity on a range of weeds. It seemed to do a good job on the wireweed and on the ryegrass.”

He said the 2021 season was tight at the start in April but was helped with excellent rainfall from May onwards which assisted the weed control of the pre-emergent herbicides.

“At the end of the year, they probably started to run out a little bit, with the extended rain and wetness.”

“With Overwatch® Herbicide, we did see weeds bleaching late in the season, especially things like milk thistle. It just really stood out.”

Mr Edis said the wet, low-light conditions of the year also challenged the crops.

“We probably had nearly six weeks without sunlight. It’s had an impact. Some of our TT canola still had good pod depth, but they’re not very tall. I think we’d probably see that from a low light intensity and the barley probably really suffered during those wetter, cloudy conditions.”

He said the addition of a new mode of action pre-emergent herbicide was positive for the industry.

“We just need to rely on our pre-emergents. We need to get them to work as best as they can for the best results. Having the different groups and being able to mix them around is where we aim to be.”

Article written by FMC for Seasons magazine.

FMC and Overwatch are registered trademarks of FMC Corporation or an affiliate. ©2021 FMC Corporation. All rights reserved 11/21.

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