Spraying cold herbicide in the heat – Does it affect ryegrass?

Aaron Preston1,3, John Broster2,3

1 NSW DPI, Wagga Wagga Agricultural Institute Pine Gully Rd, Wagga Wagga, NSW, 2650, aaron_preston@outlook.com

2 Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW, 2678

3Graham Centre for Agricultural Innovation, Locked Bag 588, Wagga Wagga, NSW 2678, Australia


Herbicide spray temperature has been shown to impact efficacy of control in giant ragweed (Ambrosia trifida L.), canadian fleabane (Conyza canadensis (L.) Cronq.), palmer amaranth (Amaranthus palmeri S. Wats) and pitted morning glory (Ipomoea lacunose L.). This study examined whether a similar effect could be found for annual ryegrass (Lolium rigidum Gaud.), the most economically damaging weed in Australia. Two herbicides, clethodim and glyphosate were each mixed with water at 5, 10, 15 and 20°C before being immediately applied to annual ryegrass at two development stages, 2-3 leaf and tillering. Comparison of biomass 21days after herbicide application showed no difference in efficacy due to temperature for either herbicide at either growth stage. This indicates that low temperature herbicide treatments do not effect control of annual ryegrass plants growing in warm conditions.


The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

Photo Credits

David Marland Photography david_marland@hotmail.com Southern Farming Systems Agriculture Victoria

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