Abstract
AbstractThe increased use of insecticide seed treatments in rice has raised many questions about the potential benefits of these products. In 2014 and 2015, a field experiment was conducted near Stuttgart and Lonoke, AR, to evaluate whether an insecticide seed treatment could possibly lessen injury from acetolactate synthase (ALS)–inhibiting herbicides in imidazolinone-resistant (IR) rice. Two IR cultivars were tested (a hybrid, ‘CLXL745’, and an inbred, ‘CL152’), with and without an insecticide seed treatment (thiamethoxam). Four different herbicide combinations were evaluated: a nontreated control, two applications of bispyribac-sodium (hereafter bispyribac), two applications of imazethapyr, and two applications of imazethapyr plus bispyribac. The first herbicide application was to two- to three-leaf rice, and the second immediately prior to flooding (one- to two-tiller). At both 2 and 4 wk after final treatment (WAFT), the sequential applications of imazethapyr or bispyribac plus imazethapyr were more injurious to CLXL745 than CL152. This increased injury led to decreased groundcover 3 WAFT. Rice treated with thiamethoxam was less injured than nontreated rice and had improved groundcover and greater canopy heights. Even with up to 32% injury, the rice plants recovered by the end of the growing season, and yields within a cultivar were similar with and without a thiamethoxam seed treatment across all herbicide treatments. Based on these results, thiamethoxam can partially protect rice from injury caused by ALS-inhibiting herbicides as well as increase groundcover and canopy height; that is, the injury to rice never negatively affected yield.
Highlights
IntroductionRed rice (Oryza sativa L.) is difficult to control due to herbicide resistance and can cause up to 82% yield loss as well as reductions in quality (Diarra et al 1985)
Season-long weed interference can cause significant yield loss in rice (Smith 1988)
Red rice (Oryza sativa L.) is difficult to control due to herbicide resistance and can cause up to 82% yield loss as well as reductions in quality (Diarra et al 1985)
Summary
Red rice (Oryza sativa L.) is difficult to control due to herbicide resistance and can cause up to 82% yield loss as well as reductions in quality (Diarra et al 1985). IR rice increased to 68% of total rice hectares in Arkansas in 2011; since herbicide resistance has resulted in a reduction to < 50% of planted hectares in recent years (Hardke 2016; Hardke and Wilson 2013). Since the discovery of IR rice in 1993, injury has been observed in some cultivars following application of acetolactate synthase (ALS)–inhibiting herbicides (Croughan 1994; Levy et al 2006). Imazethapyr, an ALS-inhibiting herbicide labeled for use in IR rice, can cause crop injury following treatment, especially when applied to hybrid rice. ‘CL161’, an inbred cultivar, had 6% and 5% injury when treated with imazethapyr at the one- to two-leaf and three- to four-leaf stages, respectively (Levy et al 2006)
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