A grower survey of weeds and herbicide use in the New South Wales cotton industry

In 1989, 52 cotton growers from the 7 major cotton areas of New South Wales were surveyed regarding their weed-control costs, major weed problems and herbicide use. This paper presents and discusses the major results from this survey. On average, weed control costs the cotton grower $A187/ha annually, the major components being $76/ha for cotton herbicides and $67/ha for hand chipping. The major cotton weeds are Xanthium occidentale, X. spinosum, Cyperus spp., Physalis spp. and Ipomoea lonchophylla. Although these weeds affect a large proportion of the cotton-growing area, their incidence is generally stable or declining under the current management systems. However, Cyperus spp., which presently affect 15% of the cotton area, are escaping the weed management practices and rapidly becoming the major weed problem in many fields. Diplachne fusca is a major weed on irrigation channels and is not controlled by the registered herbicides. Trifluralin, diuron and fluometuron herbicides are used in cotton by over 60% of cotton growers. Glyphosate is used by 59% of growers in fallows prior to cotton, and atrazine, diuron and glyphosate are used on irrigation channels by over 60% of growers. Generally, cotton growers are dissatisfied with t h e high cost of weed control and the ineffectiveness of control of some problem weeds such as Cyperus spp.