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Source: GRDC's The Crop Doctor

University of Western Australia researchers discovered that pollen from herbicide resistant ryegrass can travel up to 3000 metres due to pollen drift, confirming Western Australia's graingrowers’ fears that herbicide resistance can move between farms.

Graingrowers should therefore be even more vigilant about herbicide resistance prevention and management strategies to not only help their own crops, but their neighbours’ as well.

Preventing herbicide tolerance is responsible farming and means growers won’t potentially contribute to their neighbours’ chemical bills.

While investigating pollen mediated gene flow and its relationship to herbicide resistant ryegrass, Grains Research and Development Corporation (GRDC) supported WA Herbicide Resistance Initiative (WAHRI) researchers, Dr Roberto Busi and Professor Stephen Powles, found cross pollination occurred in favourable weather conditions.

Gene flow by pollen in ryegrass leads to highly mobile herbicide resistance, especially with high rainfall and wind, so strategies are required to minimise pollen production, dispersal and cross-pollination.

In GRDC supported field trials, plants were sprayed with 15g/ha of sulfometuron to assess resistance levels and susceptible plants were planted at varying distances up to 4000 metres from wheat and pasture paddocks infested with herbicide resistant annual ryegrass plants.

Cross-pollination results in 2005 established that gene flow resistance occurred by natural movement of resistant pollen over distances of up to 3000 metres.

It was previously thought that ryegrass pollen was only viable within 30 metres of the source plant.

The 2006 study was largely inconclusive due to drought, however the field experiment will be repeated this year if and when growing conditions improve.

Dr Busi reported that assessing long distance resistance gene flow in commercial field conditions was critical to understanding the dynamics of resistance movement. 

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