Weed Management Practices and Needs in Arkansas and Mississippi Rice

Abstract

Crop consultants in Arkansas and Mississippi were sent a direct-mail survey in fall of 2011 with questions concerning weed management in rice. The goal of the survey was to document the extent of imidazoline-resistant rice hectares, the herbicides most commonly recommended in rice, the weeds perceived to be most troublesome in rice including those resistant to herbicides, and suggested areas of research and educational focus that would improve weed management in rice. When appropriate, results from this survey were compared to a similar survey conducted in 2006. Completed rice surveys were returned by 43 consultants, accounting for 179,500 ha of scouted rice or 38% of the rice hectarage in Arkansas and Mississippi. Imidazolinone-resistant rice was grown on 64% of the hectares, and this technology was used continually for the past 5 yr on 11% of the rice hectares. Of the area planted to imidazolinone-resistant rice, 42% of this hectarage was treated solely with an acetolactate synthase (ALS)-inhibiting herbicide. Consultants listed improved control options for barnyardgrass and Palmer amaranth as the most important research and educational need in rice. The top five weeds in order of importance were (1) barnyardgrass, (2) sprangletops, (3) red rice, (4) northern jointvetch, and (5) Palmer amaranth. From a predetermined list of research and educational topics, consultants gave the highest ratings of importance to (1) control of herbicide-resistant weeds, (2) strategies to reduce the occurrence and spread of herbicide-resistant weeds, and (3) development of new economical herbicide-resistant rice varieties which was comparable to economical weed control options. Findings from this survey point to the overuse of imidazolinone-resistant rice and a lack of preemptive resistance management strategies such as crop rotation and use of multiple effective herbicide modes of action by some growers, which has likely contributed to selection for the ALS-resistant barnyardgrass and rice flatsedge recently confirmed in Arkansas and Mississippi rice.

Acetolactate Synthase–Inhibitor Resistance in Yellow Nutsedge (Cyperus esculentus): II—Physiognomy and Photoperiodic Response

“…The moist soil conditions commonly associated with rice culture in Arkansas would likely aid germination and establishment of this weed from seed, albeit flooding effects on yellow nutsedge seed germination are not known. Another fact that must be considered is that clomazone is the most widely used PRE herbicide in Arkansas rice today (Norsworthy et al 2013). Clomazone has no activity on sedges, which could further aid establishment of the Res biotype.…”

“…It is a tuber-forming sedge endemic in Eurasia and reported to be naturalized within the United States by 1850s (Bartlett 1889). Yellow nutsedge is an invasive and a persistent weed in well-irrigated agricultural and horticultural crops (Ransom et al 2009;Webster 2005), and a noxious weed in Arkansas rice-soybean rotations (Norsworthy et al 2013). Chemical control, particularly with acetolactate synthase (ALS)-inhibiting herbicides, in comparison to cultural and mechanical control, has been the most effective means for managing this weed species.…”

Evaluation of Quizalofop-Resistant Rice for Arkansas Rice Production Systems

“…Most of the rice grown is produced in a drill seeded, delayed flooding system, with only around 5% annually produced using a waterseeded system [3]. Hence, an effective weed control program in Arkansas begins with a preemergence residual herbicide followed by postemergence herbicide applications [4]. One of the main challenges to rice production is the ever increasing herbicide resistance found in multiple common rice weeds.…”

Acetolactate Synthase–Inhibitor–Resistant Yellow Nutsedge (Cyperus esculentus): I—Phenotypic Differences

“…In rice-soybean [Glycine max (L.) Merr.] production systems of the Mississippi Delta region, yellow nutsedge is often regarded as a difficult-to-control weed, with practitioners frequently requesting improved management options (Norsworthy et al 2013). The dominance of yellow nutsedge can be attributed to its biology.…”