Defining Optimum Herbicide Rates and Timing for Wild Oat (Avena fatua) Control in Spring Wheat (Triticum aestivum)¹

Abstract

Knowledge of optimal combinations of graminicide rate and stage of application could improve the effectiveness and net benefit of commonly used graminicides. A study was conducted at two locations in Saskatchewan, Canada, from 1994 to 1997. Factorial combinations of five graminicides (CGA 184927, fenoxaprop-p-ethyl, ICIA 0604, imazamethabenz, and flamprop-methyl), three graminicide rates (full, two-thirds, and one-third recommended label rate), and three leaf stages of wild oat (Avena fatua; two-, four-, and six-leaf) were compared to determine their effect on wild oat fresh weight, wheat (Triticum aestivum) seed yield, and net return. Wild oat fresh weight increased and wheat seed yield decreased to a greater extent at Saskatoon (median wild oat fresh weight of 56 g/m2) than at Scott (median wild oat fresh weight of 85 g/m2) when graminicide rate was reduced from the recommended label rate. Net return consistently decreased at both locations and among all graminicides when application rate was reduced from two-thirds to one-third of the recommended label rate. Imazamethabenz applied at progressively later growth stages caused greater wild oat fresh weight at both locations and reduced wheat yield and net return. Applying other graminicides at the earliest (two-leaf) stage of wild oat generally resulted in more or similar levels of wild oat fresh weight compared with delayed applications, especially at Saskatoon. With the exception of imazamethabenz, crop yield and net return were unaffected by leaf stage at both locations. The optimal graminicide rate is mostly dependent on the level of wild oat infestation, and the best time to control wild oat is dependent mostly on the particular graminicide.

Antagonismo das associações de clodinafop-propargyl com metsulfuron-methyl e 2,4-D no controle de azevém (Lolium multiflorum)

“…espécies cultivadas, é observada com freqüên-cia na literatura (Olson & Nalejawa, 1981;Deschamps et al, 1990;Holshouser & Coble, 1990;Vidrine et al, 1995;Burke et al, 2004;Scherder et al, 2005). Nos Estados Unidos, Minton et al (1989) demonstraram que a associação de clodinafop-propargyl com herbicidas inibidores da ALS comprometeu o controle de Echinochloa crus-galli em taxas que variaram de 5 a 45%.…”

“…Já em dicotiledôneas essa tolerância se dá pela insensibilidade da ACCase (Vidal & Merotto Jr., 2001). A seletividade de trigo a clodinafop-propargyl pode ser ampliada com a mistura do protetor (safener ) clo quinto cet-me xyl, que pro teg e efi cientemente o trigo e parcialmente a cevada, mas não possui efeitos sobre a aveia e o azevém (Vencill, 2002 Deschamps et al, 1990;Holshouser & Coble, 1990;Vidrine et al, 1995;Brommer et al, 2000;Burke et al, 2002;Scherder et al, 2005).…”

“…O antagonismo pode ocorrer em função da redução da absorção (Culpepper et al, 1999;Brommer et al, 2000) ou da absorção e translocaç ão dos grami nic ida s pel os lat ifo lic ida s (Holshouser & Coble, 1990). Outra possibilidade seria a redução de atividades metabólicas, como da divisão celular e do fornecimento de lipí-dios para formação da membrana, o que comprometer ia a at iv idade dos in ibidores de ACCase (Minton et al, 1989).…”

Integrated weed management systems with herbicide-tolerant crops in the European Union: lessons learnt from home and abroad

“…[35,43] Several studies have demonstrated that this tactic can maintain effective weed control and sustain economically acceptable crop yields. [44,45] Conflicting results regarding success in using reduced herbicide rates may be due to a variety of factors such as spray volume, droplet size, adjuvants, temperature, humidity, light quality, soil moisture content, weed size and weed species. [44,46] Despite its potential effectiveness, legal factors present practical challenges to the implementation of reduced herbicide rates, as a person or organization recommending reduced rates may be held liable for problems arising from their use.…”

Strategies and tactics for herbicide use reduction in field crops in Canada: A review

“…Efficacy of post-emergent herbicides is influenced by spray volume, droplet size, adjuvants, temperature, humidity, light quality, soil moisture content, weed size and weed species Holm et al 2000). More importantly, reduced rates are more likely to be consistently effective when weed densities are low, which will only occur with any regularity if the cropping system is managed to achieve this .…”