The Relationship of Goosegrass (Eleusine indica) Stage of Growth to Quinclorac Tolerance¹

Abstract

Goosegrass is considered tolerant to quinclorac. The purpose of this study was to determine whether there was a stage of growth at which it was susceptible. Stage of growth studies with goosegrass were conducted that evaluated quinclorac activity at rates of 0, 1, 2, 4, 8, and 16 kg ai/ha applied with 1% (v/v) Merge spray adjuvant. Quinclorac application stages evaluated included preemergence and one- to two-leaf, four- to five-leaf, and one- to two-tiller stage. The effects of root uptake from postemergence applications were also evaluated by comparing treatments with and without a vermiculite soil barrier. Goosegrass was more susceptible to quinclorac when applied preemergence or early postemergence at the one- to two-leaf stage than at later more mature stages. The importance of root uptake on quinclorac activity was also observed, particularly at the four- to five-leaf stage, where the dose required to reduce growth 50% (GR50) in the absence of the soil barrier was 3.4 kg/ha vs. 16 kg/ha in the presence of a barrier. At the most advanced growth stage of one to two tillers, calculated GR50 values were greater than 16 kg/ha whether a soil barrier was present or not. The lowest calculated GR50 value of 2.7 kg/ha for the one- to two-leaf stage with no soil barrier was still approximately 3.5 times higher than the maximum labeled rate for turfgrass.

Response of Four Improved Seeded Bermudagrass Cultivars to Postemergence Herbicides during Seeded Establishment1

“…According to registration recommendations (Anonymous 2002), quinclorac can be applied to newly seeded bermudagrass as long as methylated seed oil is withheld until 28 d after emergence. Quinclorac effectively controls crabgrass but not goosegrass (Zawierucha and Penner 2001). To the contrary, foramsulfuron provides little control of crabgrass sp.…”

Manejo de capim pé-de-galinha em lavouras de soja transgênica resistente ao glifosato

“…O efeito da época de aplicação de herbicidas, em capim pé-de-galinha, também foi relatado em plantas tolerantes ao herbicida quincloraque (Zawierucha & Penner, 2001). As plantas foram mais sensíveis ao quincloraque quando receberam a aplicação do herbicida em estádio de uma ou duas folhas, em comparação à aplicação no estádio de três ou quatro folhas, ou de um ou dois afilhos, o que confirma que a espécie apresenta capacidade diferencial de metabolização do herbicida de acordo com a fase de crescimento.…”

Optimizing activity of herbicides at reduced rate on Emex spinosa campd. with adjuvants

“…Herbicide rate reduction is a research priority to minimize environmental hazards and to increase the cost/benefit ratio (Woznica, 1995). Herbicides application rates can be reduced by up to 75%, usually when applications are made during early growth stages (Zawierucha & Penner, 2001b) or in combination with adjuvants (Lu et al, 2005;Zawierucha & Penner 2001a). However, successful control using reduced herbicide rate depends on the herbicide being applied and specific characteristics of the target weed (Bunting et al, 2004).…”