Caution urged with pre-harvest herbicide applications

The topsy turvey season has industry watch-bodies urging growers to read their herbicide labels very carefully before applying a late dose

Grain growers are being encouraged to exercise caution when undertaking pre-harvest application of herbicides in this year’s winter crops.

Growers applying herbicides late in the season to manage weeds, prevent weeds setting seed or to desiccate crops to accelerate or even-up ripening must adhere to herbicide label recommendations and withholding periods to avoid the presence of chemical residues in delivered cereal, pulse and oilseed grains.

To support growers and their advisers in ensuring late season herbicide application is carried out in a responsible manner, the Grains Research and Development Corporation (GRDC) has published a revised Pre-Harvest Herbicide Use Fact Sheet.

The Fact Sheet emphasises the importance of knowing the maximum residue limits (MRLs) of domestic and international markets and outlines the product registrations for pre-harvest weed control and desiccation, which vary according to crop type.

GRDC Senior Manager Crop Protection, Ken Young, says application of herbicides close to harvest increases the possibility of detectable herbicide residues being present in harvested grain.

“In some situations, markets have extremely low or even zero tolerance to some herbicide and pesticide residues.

“It is therefore critical that growers know the destination of their grain and that particular market’s MRLs to determine which, if any, herbicides are permitted for use on their crop late in the season,” Dr Young said.

“MRLs vary according to herbicide, crop and market, and compliance with Australian MRLs does not guarantee the grain will meet an importing country’s MRL.

“Breaches of MRLs can lead to rejected grain, so growers should seek advice from their grain buyers before they undertake late application of herbicides.”

The Pre-Harvest Herbicide Use Fact Sheet can be viewed and downloaded via the GRDC website at