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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #298540
Title: Influence of carrier volume and nozzle selection on Palmer amaranth control

Author
item BERGER, SARAH - University Of Florida
item DOBROW, MICHAEL - University Of Florida
item FERRELL, JASON - University Of Florida
item Webster, Theodore

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/2014
Publication Date: 7/1/2015
Citation: Berger, S., Dobrow, M., Ferrell, J., Webster, T.M. 2015. Influence of carrier volume and nozzle selection on Palmer amaranth control. Peanut Science. 41(2):120-123.

Interpretive Summary: Palmer amaranth is listed as the most troublesome weed in peanut production in Florida, Georgia, and South Carolina, with season-long competition resulting in 28% yield loss. Rapid growth rate of Palmer amaranth, when compared with other Amaranthus spp., combined with seed production of up to 1.2 billion seed ha-1, necessitate the need for effective control of this weed. In-season weed management in peanut often relies on postemergence herbicides. However, many of these do not provide season-long control of Palmer amaranth. The protoporphyrinogen oxidase (PPO) inhibiting herbicides aciflourofen and lactofen are often the only postemergence options for growers attempting to control Palmer amaranth in peanut. Spray technology has evolved toward faster moving spray equipment and lower carrier volumes in an effort to reduce fuel costs from transporting large quantities of water and the need to cover more hectarage per fill up. In an effort to reduce the drift potential of these faster moving sprayers, many growers employ the use of drift-reducing nozzles. Air induction (AI) nozzles, for example, produce larger droplets, which are less susceptible to drift, than conventional nozzles at the same pressure. Current knowledge is limited on effect of application practices on Palmer amaranth control with contact herbicides. Lactofen is a postemergence PPO inhibiting herbicide that is commonly used to control Palmer amaranth in peanut. Application at 5-10 cm Palmer amaranth with 94, 187, or 281 L ha-1provided >90% control. Applications made to 15-20cm weeds provided less control. This demonstrates the critical timing of contact herbicide application to control Palmer amaranth. Applications made to smaller weeds provided sufficient control at any carrier volume tested, while applications made to larger weeds were least effective at 94 L ha-1. Adequate coverage is essential for maximizing efficacy with contact herbicides. These data indicate that applications made at 94 L ha-1 can result in reduced control when treating 15-20 cm tall Palmer amaranth plants. But of greater importance is the fact that greater than 90% control was achieved, regardless of nozzle type or carrier volume, when 5-10 cm tall plants were targeted. Therefore, it is essential that peanut producers regularly scout fields and monitor Palmer amaranth height if contact herbicides such as lactofen are to be used.

Technical Abstract: Palmer amaranth (Amaranthus palmeri S Wats.) is largely viewed as one of the most troublesome weeds in the southeast. Effective control is essential in order to avoid reductions of crop yield. Due to wide-spread resistance to the ALS chemistry, postemergence contact herbicides are often the only in-season option to control Palmer amaranth in peanut. Lactofen is a postemergence protoporphyrinogen oxidase inhibiting herbicide that is commonly used to control Palmer amaranth in peanut. A factorial treatment structure of carrier volume (94, 187, 281 L ha-1), nozzle selection (AI Teejet® and XR Teejet®), and application timing (5-10 cm weeds and 15-20 cm weeds) was conducted in 2008 in Williston, FL and in 2012 in Tifton, GA to determine the best control strategy with this contact herbicide. Palmer amaranth control was recorded 7, 14, and 21 days after treatment (DAT). Nozzle selection was not significant as a main effect or as an interaction at any location. However, the carrier volume by application timing interaction was significant at each location. In 2008 at Williston, FL and in 2012 at Tifton, GA application at 5-10 cm Palmer amaranth with 94, 187, or 281 L ha-1provided >90% control. Applications made to 15-20cm weeds provided less control. This demonstrates the critical timing of contact herbicide application to control Palmer amaranth. Applications made to smaller weeds provided sufficient control at any carrier volume tested, while applications made to larger weeds were least effective at 94 L ha-1.