Tolerance of rhizoma perennial peanut to glyphosate and triclopyr

Abstract

Rhizoma perennial peanut (RPP) is well adapted to the Gulf Coast region of the U.S., but its varietal tolerance to glyphosate and triclopyr is not well defined. The research was conducted to determine the effect of various rates of glyphosate and triclopyr on established RPP, and the response of common RPP varieties to these herbicides. The RPP sward was approximately 7 year younger at Zolfo Springs than at Ona location. RPP showed moderate tolerance to glyphosate and triclopyr application, and injury level did not differ with the age of RPP sward. However, the biomass production was negatively influenced by the age of the RPP sward. Overall, injury from glyphosate applications did not exceed 40% for both sites. The glyphosate rate for 20% biomass reduction was predicted to be 0.53 and 2.17 kg ae ha-1 at Zolfo Springs and Ona, respectively. RPP injury from triclopyr was greater in Zolfo Springs than at Ona, and the triclopyr rate predicted to result in a 20% biomass reduction was 0.45 and 0.99 kg ae ha-1 at Zolfo Springs and Ona, respectively. There was a difference on RPP varieties response to glyphosate and triclopyr application. ‘Florigraze’ and ‘Ona 33’ were less tolerant to glyphosate compared to ‘UF-Tito’ and ‘Ecoturf’ at 30 DAT. Likewise, UF-Tito’ and ‘Florigraze’ were less tolerant to triclopyr compared to Ona 33 and Ecoturf. Overall, Florigraze showed highest injury and at least 2-fold reduction on biomass compared to the other three varieties from glyphosate or triclopyr application. Results from this research indicates that glyphosate and triclopyr appear to be safe to apply to long-established RPP stands, but herbicide rate and RPP varieties should be considered if stands are <5 yr old.