RECENT rain has instigated a considerable amount of summer spraying across the region, as growers attempt to control summer weeds and retain precious moisture for this year's crops.
However, as reported by BCG farmer advisory committee members at meetings held in the Wimmera and Mallee, many common summer weeds are proving difficult to control.
With glyphosate resistant ryegrass becoming an increasing issue for growers, BCG worked with Clovercrest Consulting at Lillimur (west of Kaniva) last year to investigate a range of alternative knockdown herbicide options.
The field trial, supported by the Grains Research and Development Corporation, was established adjacent to a paddock containing a confirmed population of glyphosate resistant ryegrass.
Treatments included a range of commonly used knockdown herbicides (and combinations) applied at a range of rates. Water rates and about spraying timing were also looked at.
The trial, which compared the effectiveness of glyphosate on ryegrass, with other knockdown herbicides (and mixes) containing the active constituents paraquat, amitrole, prosulfocarb, S-metolachlor and oxyflurofen, clearly showed how important glyphosate is to the grains industry, but how quickly its usefulness is diminishing.
BCG senior researcher Kelly Angel said the presence of surviving weeds (after spraying) in this trial highlighted that growers cannot afford to be complacent about its (glyphosate) use. In this trial the 'double knock' strategy (where weeds receive two sprays) achieved the best control.
"The trial also revealed options that could make this strategy more robust. The majority of double knock spray programs are currently carried out with paraquat applied on its own as the second spray," Ms Angel said.
In this trial the 'double knock' strategy achieved the best control.
- Kelly Angel, BCG
"This trial showed that by using other mixes, potentially as a double knock following a glyphosate application, it is possible to improve control at only slightly greater expense than by using paraquat alone."
Further to this, Ms Angel said the trial confirmed that paraquat-based products delivered the best results when used with high water rates (100l/ha plus) with a medium to coarse droplet to manage drift and when the second application occurred no more than 10 days after the first.
"A small amount of systemic action can also be obtained if spraying is carried near evening, which allows the product to spread overnight in the leaf before being activated by the sun the next day.”
A full report is available in the 2015 BCG Seasons Research Results compendium and will also be discussed at the Trials Review Day on February 19.
