Using IWM to keep one step ahead of resistance

Ben Thomas has been growing cotton for 15 years across three properties, two irrigated and one broadacre, at Warren in the Macquarie Valley. Speaking to his CottonInfo Regional Extension Officer, Ben Thomas outlined how he is managing the threat of resistant weeds.

The most common weeds found on Ben’s properties are fleabane, windmill grass, barnyard grass, sow thistle, turnip weed and ryegrass. Fleabane and windmill grass are the biggest challenges at present, with Ben expecting ryegrass, sow thistle, barnyard grass and feathertop Rhodes grass to emerge as issues in the future.

Ben Thomas

The threat of resistance is a core reason why Ben has an integrated management plan in place, developed with consultant Andrew Cooper of Landmark.

Ben’s approach is to control weeds in his irrigated cotton through a range of tactics including pre-emergent knock downs, post-emergent herbicide applications, layby residuals and cultivations. Chipping is used if required.

The pre-emergents and laybys are used sparingly, as high disease levels and cold temperatures can lead to a slow start for the cotton, and he does not want to put any additional stress on the plant.

He calculates that the cost for controlling weeds ranges from $50 to $80 per hectare across his fallow, broadacre and irrigation country.

Through CottonInfo, Ben has tested for resistance in fleabane, ryegrass and other weeds.

Grower Ben Thomas
Cropping area Total hectares: 6000 ha. Cotton: 1500 ha irrigated
Soil type Cracking clay
Rotations Two-year rotation: cotton (summer); winter cereal or legume (winter); long fallow (sum- mer and winter); cotton (summer)

Source: CottonInfo Weed Control case studies

Further information: CottonInfo weed management page

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