Agricultural authorities have encouraged Wimmera farmers to help tackle the spread of brome grass in the region.

Agriculture Victoria has continued an awareness campaign regarding the weed after a series of workshops in partnership with Wimmera Catchment Management Authority and Wimmera Farming Network.

Speaking at the workshops, South Australian weeds research scientist Dr Sam Kleemann said there was need for a concerted three-year effort on brome grass to overcome this serious weed on grain farms.

“Only 20 years ago, brome grass was not classed as a weed of significance in the region. Now it causes $20-million in lost cereal yield each year across south-eastern Australia, of which $4.5-million is in the Wimmera alone,” he said.

“This does not include the costs of controlling the weed.”

Brome is a highly competitive weed and can reduce wheat yields by 30 to 50 percent with only 100 plants per square metre.

It has proliferated with the adoption of no-till farming, early sowing and dry sowing. The weed can produce multiple germinations each year. 

Dr Kleemann said brome grass had evolved in modern farming systems with higher levels of seed dormancy, making management more difficult. 

“You don’t need a lot of plants to inflict a lot of pain,” he said. 

“It is a competitive weed and can severely reduce yields with the presence of only low weed numbers.

“Brome grass populations have evolved to withstand modern farming practices by becoming more dormant and germinating later, making them harder to control. For example, brome grass populations in crops can germinate an average 20 days later than when found along fence lines.”

Dr Kleemann said about 25 percent of the seedbank failed to germinate in any season and instead carried over into the next year, making longer-term management important. 

“Fortunately most seed only survives up to three years,” he said.

He said even after the first year of applying brome grass controls, there was still enough viable seed to kickstart the population. 

“If you take your foot off the brake, then even in a dry year brome grass can produce more than 8000 seeds per square metre and about a quarter of the seeds will carry over into the next season without germinating,” he said.

“So, with significant brome patches where seedbanks are large you need a minimum of three years of control to make an impact.”

Grower advice is to use a range of tactics to drive weed numbers down. In addition to herbicides, growers can employ non-chemical control methods such as harvest weed-seed control. 

While resistance to selective herbicides is still low in brome grass, growers should identify whether any apparent herbicide failure was application-related, resistance or both. 

Growers are also encouraged to test for herbicide resistance when herbicides do not work.

Dr Kleeman said pulse crops or vetch were good options in the first year of brome grass control, enabling growers to use a grass-selective herbicide and crop-top. 

“Hay cutting and chemical fallow tactics are also helpful, reducing brome grass numbers by 95 percent. In the Mallee, some growers opted to spray out patches of brome grass in crops before it set seed,” he said.

More information is available online at agriculture.vic.gov.au or on the GRDC website, grdc.com.au. 

The entire April 29, 2020 edition of The Weekly Advertiser is available online. READ IT HERE!

The entire April 29, 2020 edition of AgLife is available online. READ IT HERE!