GRDC Podcast

A five-year survey of the entire Australian cropping belt has revealed a sobering picture of growing herbicide resistance in key cropping weeds.

Dr John Broster from the Graham Centre for Agricultural Innovation heads up a joint herbicide resistance monitoring project between Charles Sturt University, Queensland Department of Agriculture and Fisheries and the Universities of Adelaide and Western Australia.

In a 5-year cycle the group visited 3000 randomly selected paddocks and took 2000 samples of the nation’s number one weed, ryegrass, which is followed by wild radish in WA, wild oats in Queensland and NSW, and sow thistle in fourth place.

The survey revealed that nationally, about 75 per cent of the populations of ryegrass are resistant to Group A ‘fop’ herbicides, ranging from 99 per cent in WA and 90 per cent in southern NSW around Wagga to much lower levels in western NSW where cropping intensity is a bit lower, and in northern NSW where cropping systems are different.

In the last five-year survey, the level of resistance in ryegrass around Wagga was 70-75 per cent, but John says the numbers can vary as the survey monitors different paddocks.

But the most concerning discovery was the increasing resistance to the most important herbicide, glyphosate. Across Australia glyphosate resistance is 5 per cent in the populations of ryegrass, but in a region like the Liverpool Plains in NSW it was in 29 per cent of the populations that were surveyed.

John says if growers lose glyphosate, they’ll have to use more complex, more expensive methods of controlling weeds.

He says the key to remember is that if you use herbicides, you will get resistance.

By using other methods to control plants that survive herbicide applications and prevent them from setting seed, then growers will slow – maybe not stop, but slow – the development of resistance to enable the use of herbicides for longer.

Paddocks are selected at random for the survey to provide an indication of what herbicides are still working and where, and what are at risk in the future. John says farmers generally are responsible in their management of weeds.

Even though there are high levels of resistance in the ryegrass to selective herbicide groups, and even glyphosate, at harvest time when researchers collect the weed seeds, most populations are below one plant per square metre.

So even though it’s more complicated, he says they’re managing populations quite well using alternative herbicides and other methods than herbicides to control the weed populations.

Dr John Broster

Herbicide Resistance Screening

Charles Sturt University

Wagga Wagga, NSW

02 6933 4001 or 0427 296 641

[email protected]

• https://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2018/03/a-survey-of-herbicide-resistance-in-key-weeds-across-the-northern-grains-region

Learn more about your ad choices. Visit megaphone.fm/adchoices

Another of the speakers at the Henty Field Days grower forum was NSW DPI’s research agronomist Graeme Sandral. Graeme spoke about the seed quality issues that can result from a tough season and how they impact next year’s grain yield.

In this podcast Graeme Sandral also discusses crop nutrition and fertiliser management next season. Graeme points out that because less nutrient will leave the paddock, due to less grain being produced, the unused Nitrogen and Phosphorus left behind in the soil should be factored into next season’s fertiliser needs.

Learn more about your ad choices. Visit megaphone.fm/adchoices

Grain growers attending this year’s Henty Field days had the opportunity to hear timely advice from specialists such as NSW DPI’s southern pastures program leader Nigel Phillips. Nigel was one of four speakers at the GRDC NSW DPI Tough Season Questions Answered forum, held as part of the field days.

After addressing the forum Nigel Phillips recorded this podcast and summarised the messages he delivered. His key message was to have an action plan, follow it through and don’t regret making a choice.

Nigel also advised growers to think about options. Just because a crop has been impacted by drought or a frost event it doesn’t mean the crop is worthless. These crops can still be a valuable source of livestock feed, high in energy and protein.

Learn more about your ad choices. Visit megaphone.fm/adchoices

Lessons learnt from past droughts and frosts events need to be applied to this season, especially in regards to determining the feed quality of a crop. This was some of the advise passed onto grain growers by NSW DPI Feed lab chemist Richard Meyer at the Henty Field Days grain grower forum.

The forum was organised by GRDC and NSW DPI to provide growers with an opportunity to get good farm management advise during a tough season.

As you’ll hear in this podcast data kept from feed samples taken from previous drought stressed and frost damaged crops provides a valuable reference point for when to cut for hay or silage to optimism your crop’s feed quality.

Learn more about your ad choices. Visit megaphone.fm/adchoices

At the recent southern NSW, Henty Field Days, GRDC with NSW DPI presented a special grower forum called Tough Season Questions Answered. The idea of the forum was to give grain growers an opportunity to hear timely advise on crop management decisions and have their questions answered.

One of the speakers was Dr Felicity Harris a Cereal Physiologist with NSW DPI who highlighted the need to identify biomass in paddocks so that informed decisions could be made to either take a crop through to harvest, cut for fodder, silage, or to consider grazing options.

In this podcast Dr Harris encourages growers to measure biomass at both a paddock and farm scale sand to be aware of any underlying damage that might have been caused by frost events.

Learn more about your ad choices. Visit megaphone.fm/adchoices