American Journal of Plant Sciences, 2014, 5, 153-157 Published Online January 2014 (http://www.scirp.org/journal/ajps ) http://dx.doi.org/10.4236/ajps.2014.51020 Weed Management in Spring Planted Cereals with Mesotrione Nader Soltani, Christy Shropshire, Todd Cowan, Peter H. Sikkema University of Guelph Ridgetown Campus, Ridgetown, Canada. Email: soltanin@uoguelph.ca Received October 16 th , 2013; revised December 18 th , 2013; accepted January 7 th , 2014 Copyright © 2014 Nader Soltani et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In accor- dance of the Creative Commons Attribution License all Copyrights © 2014 are reserved for SCIRP and the owner of the intellectual property Nader Soltani et al. All Copyright © 2014 are guarded by law and by SCIRP as a guardian. ABSTRACT There is little information on the efficacy of mesotrione for the control of broadleaved weeds in spring planted cereals under Ontario environmental conditions. A total of eight studies were conducted in Ontario over a two- year period (2010 to 2011) to evaluate cereal tolerance and weed control efficacy of mesotrione applied preemer- gence (PRE) at 25, 50, 100, 140, and 280 g ai ha −1 in spring planted barley, durum wheat, oats, and wheat. Meso- trione, applied preemergence at the rates evaluated, caused no injury in either year in spring planted barley, durum wheat, oats, or wheat evaluated at 1, 2 and 4 week after emergence (WAE). The predicted mesotrione rate required to give adequate control of AMBEL, CHEAL, POLCO and SINAR was generally greater than 280 g ai ha −1 . The average yield of the weedy check was 81% of the weed-free check. According to the exponential to maximum regression, the mesotrione rates required to give 90%, 95% and 98% of the weed-free check were 15, 30 and 45 g ai ha −1 , respectively. To provide yield equivalent to the standard treatment of bromoxynil/MCPA, 36 g ai ha −1 of mesotrione was needed. Based on these results, mesotrione applied preemergence at 25, 50, 100, 140, and 280 g ai ha −1 can be safely used in spring planted barley, durum wheat, oats, and wheat. However, greater than 280 g ai ha −1 of mesotrione was needed to adequately control AMBEL, CHEAL, POLCO and SINAR. KEYWORDS Barley; Durum Wheat; Height; Herbicide Sensitivity; Oats; Tolerance; Yield; Wheat 1. Introduction In recent years, cereal production has increased in On- tario because of new, improved cultivars, reduced-till production systems and increased prices. Cereals includ- ing spring planted barley (Hordeum vulgare L.), durum wheat [Triticum turgidum subsp. durum (Desf.) Husn.], oats (Avena sativa L.) and wheat (Triticum aestivum L.) are also ideal crops to include in the rotation as they help to maintain soil structure and break weed cycles. One of the most significant aspects of spring cereal production is weed management [1]. Herbicides registered in cereals have not changed appreciably in the past 20 years in On- tario [2]. Postemergence (POST) herbicides such as 2,4-D, MCPA, bromoxynil/MCPA, dicamba/MCPA/ mecoprop, dichlorprop/2,4-D and thifensulfuron-methyl/ tribenuron-methyl are still being used, either alone or in combination for the control of broadleaved weeds in cereals [2,3]. There have been reports of crop sensitivity in cereals with some of these herbicides in cereals [4]. Currently, there are no soil applied residual herbicides available for annual grass and broadleaved weed control in spring planted barley, durum wheat, oats and wheat in Ontario. More research is needed to determine tolerance and weed control efficacy of spring planted cereals to recently developed herbicides with a novel mode of ac- tion. Mesotrione is a triketone that inhibits the p-hydroxy- phenylpyruvate dioxygenase (HPPD) enzyme responsi- ble for catalyzing the conversion of tyrosine to plasto- quinone and α-tycopherol [5-7]. Mesotrione can be ab- sorbed by the germinating seed, emerging root and shoot and is translocated in the xylem and phloem [8]. Meso- trione controls broadleaved weeds including Amaranthus OPEN ACCESS AJPS