WHAT was once considered a winter problem, common sowthistle, has become an issue all year round and is now one of the most widespread, broadleaf weeds in southern Queensland and northern New South Wales.

For the past 18 months the Northern Grower Alliance, as part of a Grains Research and Development Corporation research investment project, has been investigating the challenges of safe, effective and economical control of common sowthistle or Sonchus oleraceus.

NGA's research manager Lawrie Price said the increasing common sowthistle problem was largely a result of the fact its seed was readily dispersed by wind.

"Growers are also now starting to battle glyphosate-resistant populations,” he said.

"In recent years, weed control in summer fallow has become an increasingly difficult and expensive component of northern farming systems.

"This is in part due to a heavy reliance on glyphosate, which has led to the selection of weed biotypes which are glyphosate-resistant.

"So we now need to develop non-glyphosate-based management strategies to effectively, safely and economically control common sowthistle.”

GRDC's most recent investment into this weed has seen NGA researching weed management using residual, knock-down and double knock approaches.

Products currently registered for residual control of common sowthistle in fallow include Balance® and Terbyne Xtreme®.

Mr Price said when it came to problematic weeds, like common sowthistle, effective management could have an impact on crop profitability so growers needed to focus on individual paddocks and adjust rotations to suit conditions and also allow for residual herbicide use in-crop.