Corn and Rice Response to Simulated Drift of Imazethapyr Plus Imazapyr

Abstract

Field research was conducted for 2 yr to evaluate response of corn and rice to simulated drift rates of a commercial premix of imazethapyr plus imazapyr [3:1 (w/w)]. Drift rates of the imazethapyr plus imazapyr premix represented 0.8, 1.6, 3.2, 6.3, and 12.5% of the usage rate of 63 g ai/ha (0.5, 1, 2, 4, and 7.9 g/ha, respectively). The imazethapyr plus imazapyr premix applied to six-leaf corn at 7.9 g/ha reduced height 11% compared with the nontreated control 7 days after treatment (DAT) but did not affect corn height 14 and 28 DAT. Corn yield was equivalent regardless of imazethapyr plus imazapyr rate and ranged from 10,200 to 11,500 kg/ha. At 28 DAT, rice height was reduced 12% when 7.9 g/ha of the imazethapyr plus imazapyr premix was applied early postemergence (EPOST) at two- to three-leaf and 14 and 5% when the imazethapyr plus imazapyr premix at 7.9 and 4 g/ha, respectively, was applied late postemergence (LPOST) at panicle differentiation. Reductions in mature rice height of 11 and 6% were observed when the imazethapyr plus imazapyr premix was applied LPOST at 7.9 and 4 g/ha, respectively, and a 5% reduction was observed for 7.9 g/ha of the imazethapyr plus imazapyr premix applied EPOST. Application of the imazethapyr plus imazapyr premix EPOST at 7.9 g/ha delayed heading in only 1 yr, but heading was delayed both years when applied LPOST. Rice yield was reduced 39 and 16% when the imazethapyr plus imazapyr premix was applied LPOST at 7.9 and 4 g/ha, respectively, compared with a 9% yield reduction for 7.9 g/ha applied EPOST.

Tolerância de cultivares de arroz irrigado (Oryza sativa) ao herbicida nicosulfuron e à mistura formulada de imazethapyr + imazapic

“…Esses resultados podem ser explicados pelo fato de o cultivar IRGA 422CL ser derivado de uma linhagem mutada e possuir a característica de tolerância às imidazolinonas (imazethapyr + imazapic), sendo tolerante também ao grupo das sulfoniluréias (nicosulfuron), confirmando os resultados obtidos por Webster & Masson (2001). A fitotoxicidade observada no cultivar IRGA 417 demonstrou sua suscetibilidade a esses herbicidas, como foi relatado em estudos de deriva simulada na cultura do arroz (Bond et al, 2006;Kurtz & Street, 2003).…”

“…O efeito do incremento da dose herbicida resultando em aumento na fitotoxicidade foi reportado em outros estudos, tanto para cultivares de arroz tolerantes como para cultivares sensíveis (Bond et al, 2006;Kurtz & Street, 2003;Levy Jr. et al, 2006;Ottis et al, 2003;Steele et al, 2002).…”

“…) ocasionaram redução no crescimento, que levou a perdas na produtividade do arroz (Bond et al, 2006).…”

Field and laboratory assessments of sugarcane mutants selected in vitro for resistance to imazapyr herbicide

“…This suggests that the slight depression for Mut1 and Mut6, and the continued decline in activity for control N12 in the untreated area may have been due to herbicide drift from the adjacent treated plots. Eberlein and Guttieri (1994) reported that amounts as small as 1/50th of the normal agricultural imazapyr rate reduced potato yields by two-thirds and Bond et al (2006) showed that a simulated drift rate of only 8 g a.i. ha -1 could reduce rice yield by 40%.…”

Controle de arroz-vermelho (Oryza sp.) com o herbicida nicosulfuron ou a mistura formulada de imazethapyr + imazapic

“…Essa redução foi mais evidente para o herbicida imazethapyr + imazapic, que resultou em menor estatura de arroz-vermelho desde as menores doses estudadas, comparativamente ao nicosulfuron. O efeito de imazethapyr a partir de doses reduzidas também foi observado em estudos anteriores (Bond et al, 2006;Dal Magro, 2006). Da mesma forma que para a variável estatura, a massa seca da parte aérea sofreu redução com os tratamentos herbicidas, que foi mais evidente com o herbicida imazethapyr + imazapic, comparativamente ao nicosulfuron, exceto para as duas maiores doses (Figura 4).…”