Early-season applications of chlorimuron for weed control in peanut: Are the benefits worth the risk?

Authors: Johnson, Wiley - Carroll

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/12/2009
Publication Date: 3/4/2009
Citation: Johnson, W.C. 2009. Early-season applications of chlorimuron for weed control in peanut: Are the benefits worth the risk? Weed Science Society of America. Meeting Abstract 49:505

Interpretive Summary:

Technical Abstract: Chlorimuron is applied mid-season to control Florida beggarweed in peanut. Chlorimuron can be applied from 60 days after emergence (DAE) until 45 days prior to harvest. Applications are restricted to this time interval since peanut is more tolerant of chlorimuron applied mid-season than when applied early-season. However, Florida beggarweed are often too large for consistent control once peanut are old enough for treatment. Trials were conducted from 2006 to 2008 to determine if the benefit of controlling smaller Florida beggarweed with chlorimuron applied earlier in the season compensates for the risk of significant peanut injury. Main plots were chlorimuron (9 g ai/ha) applied at 21, 35, 49, 63, 77, and 91 (DAE). Additionally, flumioxazin (0.094 kg ai/ha) PRE was included as a standard treatment for Florida beggarweed, along with a nontreated control. Main plots were split into subplots; weed-free and weeds present. The only herbicide treatment that effectively controlled Florida beggarweed was flumioxazin PRE. While chlorimuron is registered on peanut specifically for Florida beggarweed control, visual control ratings ranged from 38 to 67%. Chlorimuron applied at 21 and 35 DAE was more efficacious than chlorimuron applied at later dates. In plots with weeds present, peanut treated with chlorimuron at any time of application yielded less than peanut treated with the standard of flumioxazin PRE. In plots that were maintained weed free, peanut treated with chlorimuron at any of the times of application yielded less than peanut treated with the standard of flumioxazin PRE. These data indicate that chlorimuron can be applied earlier than 60 DAE and provide better Florida beggarweed control with greater peanut yields than when applied at the recommended time intervals. However, Florida beggarweed control and peanut yields from any of the chlorimuron treatments were consistently less than the standard of flumioxazin PRE.