NEW research into how annual ryegrass weeds respond to different environmental conditions has produced concerning results.
The study, undertaken by La Trobe University’s Institute for Sustainable Agriculture and Food and School of Agriculture, Biomedicine and Environment, found that reduced water and soil moisture could make conditions better for the weed.
When comparing herbicide-resistant and herbicide-susceptible populations of ryegrass, the researchers found a lack of moisture could increase leaf growth by 132 per cent, and tiller growth by 153 per cent when compared to saturated conditions.
Dr Ali Bajwa was the lead author on the research, which was recently published in the journal Scientific Reports.
A senior lecturer in weed science and agronomy, he said the findings should spark a fresh approach to managing the pest plant.
“Annual ryegrass is already one of the most difficult weeds for Australian grain growers to control, and our study shows it has a strong capacity to adjust to moisture stress,” he said.
“The fact that the resistant populations can grow more vigorously under moderate drought and still produce seed under severe stress means growers need management strategies that are tailored to local weed populations and seasonal conditions.
“Resistant populations did not show any major fitness cost and in fact, performed better under stress, which could be a double whammy for grain growers who are having to deal with herbicide resistant plants that are also drought-hardy”.
Dr Bajwa also said the research reinforced the idea that different settings needed different approaches to controlling ryegrass.
“Understanding how different ryegrass populations respond to drought can help growers and advisers design more targeted strategies to reduce seedbank build-up and limit the spread of difficult-to-control populations,” he said.
“We need further research on a greater number of populations under field conditions in order to future proof our weed management programs in grain production in the wake of seasonal variabilities and changing climate.”