Demonstrating integrated weed tactic across farming systems

Abstract

Glyphosate resistance is everywhere! This ever-increasing issue facing weed management on cotton and grains systems is forcing growers to look for alternatives. None of these alternatives are as easy to incorporate into farming systems as glyphosate – a once in a century herbicide.
A series of workshops on weed management issues was held in conjunction with cotton and grain growers in the major cropping areas of the Northern Region. Aside from glyphosate and group 1 resistance, the major issue growers are facing is incorporating post-emergent herbicides into their systems. Post-emergent herbicides require knowledge of proposed crop rotations, soil type, climatic conditions, herbicide properties and incorporation requirements on top of weed spectrum.
It has been over two decades since pre-emergent herbicides were used commonly in cotton systems. It this time there has been a generational change in the growers and agronomists who aren’t confident in incorporating pre-emergent herbicides into their programs. Additionally, as optical spray technology is becoming more common, growers are now using high rates of pre- and post-emergent herbicides on patches of weeds. Some of these post-emergent herbicides can have residual properties at the rates being used.
Our research has shown that residual herbicides applied to cotton at planting had some detrimental early-season effects on the following wheat and chickpea crops however these effects did not consistently result in yield reductions. Of the range of fallow pre-emergent herbicides applied before the cotton crop, only imazapic had a detrimental effect on the cotton crop. High rates of 2,4-D that have damaged subsequent cotton commercially did not show detrimental effects in the trials we conducted. High rates of Balance, Sharpen, Starane and Voraxor that can be applied through camera sprayers are likely to cause damage to subsequent cotton crops.