Controlling weeds early in cotton is important because of the impact they can have on the crop. Competition with weed growth can reduce fiber quality, crop yield, and irrigation efficiency, and weeds can serve as hosts for insects, disease-causing pathogens, and nematodes, and increase overall production costs. During the first 8 to 10 weeks after cotton planting, weeds can out-compete cotton seedlings and cause a reduction in cotton growth and development. As weed density in cotton fields increases, the potential damage to fiber yield and quality increases. Weeds can compete for light, nutrients, and water, and in some cases release allelopathic (growth-suppressing) chemicals.1
Integrated pest management strategies that involve preventative, cultural, mechanical, biological, and chemical methods can help reduce the impact weeds have on cotton. Each strategy employs different techniques that may include crop rotation, use of cover crops, tillage, and the use of herbicides.
Weed identification is an important first step for any weed management program. Proper identification can help define the best management strategy. If herbicides are determined to be the best method, burndown, and preplant applications may be involved. Herbicide labels MUST be read to determine if timing restrictions between application and cotton planting date exist. The full recommended herbicide rate and proper application timing should be used for the toughest-to-control weed species in the field.
Weeds can germinate and emerge at different times. Therefore, it is highly recommended that a residual herbicide be used along with a burndown herbicide to provide for extended weed control. The herbicides should have different sites of action. Existing spring-time weeds should be sprayed when they are less than 4 inches in height. In addition to starting with a clean field, removing weeds after planting when weeds are less than 4 inches tall is necessary to help preserve yield potential. Sequential herbicide applications combining different sites of action, and foliar and residual activity provide the most effective weed management plans.
XtendiMax® herbicide with VaporGrip® Technology, a Restricted Use Pesticide (RUP), is labeled for burndown and preplant applications in cotton in some geographical areas (Table 1). The herbicide label and individual state notifications MUST be read and followed. XtendiMax with VaporGrip Technology applications MUST be made by dicamba-trained certified applicators. Visit XtendiMaxApplicationRequirements.com for additional information.
XtendiMax with VaporGrip Technology is a low-volatility dicamba (Group 4) formulation approved for in-crop use in cotton with XtendFlex® Technology. XtendFlex Technology is available in Bollgard II® XtendFlex® cotton technology and Bollgard® 3 XtendFlex® cotton technology, which are part of the Roundup Ready® Xtend Crop System. These two cotton technologies provide tolerance to dicamba, glyphosate and glufosinate herbicides. Tolerance to these three herbicides, each with a different site of action, provides for a weed management system that is flexible for herbicide selection and tank-mixing. Additionally, Bollgard II® XtendFlex® cotton technology provides two unique Bacillus thuringiensis (B.t.) proteins and Bollgard® 3 XtendFlex® cotton technology provides three unique B.t. proteins to protect cotton bolls from Lepidopteran insect pests.
XtendiMax with VaporGrip Technology can be used as a burndown in fields to be planted with conventional cotton at a maximum rate of 11 fl oz/acre (Table 2). There should be a minimum accumulation of 1 inch of rainfall or overhead irrigation following the application and a minimum of 21 days should occur between the application and planting of conventional cotton. The maximum combined amount of this product is 44 fl oz/acre.
1Ashigh, J., Mohseni-Moghadam, M., Idowu, J., and Hamilton, C. 2012. Weed management in cotton. Guide A-239. New Mexico State University.