Vol.2, No.4, 451-456 (2011) doi:10.4236/as.2011.24058 Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/AS/ Agricultural Sciences Sensitivity of durum wheat (Triticum turgidum) to various postemergence herbicides Nader Soltani * , Christy Shropshire, Peter H. Sikkema University of Guelph Ridgetown Campus, Main Street East, Ridgetown, Ontario, Canada; * Corresponding Author: nsoltani@ridgetownc.uoguelph.ca Received 2 September 2011; revised 15 October 2011; accepted 25 October 2011. ABSTRACT There are a limited number of herbicide options available for durum wheat production in Ontario, Canada. Four field studies were conducted in Ontario, Canada over a three year period (2008, 2009 and 2010) to evaluate the sensitivity of spring planted durum wheat to post-emergence (POST) applications of dichlorprop/2,4-D, dicamba/ MCPA/mecoprop, clopyralid, bromoxynil/MCPA, pyrasulfotole/bromoxynil, thifensulfuron/tribe- nuron + MCPA amine, fluroxypyr + MCPA ester, tralkoxydim and fenoxaprop-p-ethyl/safener at the manufacturers’ recommended dose and twice that dose. Visible injury in durum wheat were 0 to 2.4% with dichlorprop/2,4-D, 0 to 6% with dicamba/MCPA/mecoprop, 0 to 0.4% injury with clopyralid, 0 to 1.4% injury with bromoxynil/MCPA, 0 to 3.5% with pyrasulfotole/bromoxynil, 0 to 5% with thifensulfuron/tribenuron + MCPA amine, 0 to 2.6% with fluroxypyr + MCPA ester, 0 to 5% with tralkoxydim and 0.4% to 8% with fenoxaprop-p- ethyl/safener at various evaluation dates (1, 2, 3 and 4 weeks after treatment). Durum wheat height was decreased as much as 5% with dicamba/ MCPA/mecoprop, 4% with pyrasulfotole/bromoxy- nil and 6% with fenoxaprop-pethyl/safener but was not affected with other herbicides evaluated. There was no decrease in durum wheat yield with the herbicides evaluated. Keywords: Durum Wheat; Height; Herbicide Sensitivity; Injury; Tolerance; Yield 1. INTRODUCTION Durum wheat [Triticum turgidum subsp. durum (Desf.) Husn.] is the second most important Triticum species, next to common wheat (Triticum aestivum L.) [1]. Du- rum wheat has yellow endosperm, high protein content and gluten characteristics which make it popular with processors for pasta products [1]. Globally, 30 million MT of durum wheat are produced on approximately 18 million hectares of land [2]. Most of the durum wheat produced in the world (nearly 8 million MT) is grown in European Union (mainly Italy, Spain and Greece) [2]. Canada is the second largest producer of durum wheat in the world producing nearly 4.6 million MT per year fol- lowed by Turkey and the USA which produce 4 and 3.5 million MT, respectively [2]. Most of the durum wheat in Canada is produced in the provinces of Saskatchewan, Alberta and Manitoba [1]. Currently, there is limited production of durum wheat in Ontario. Most of the commercially grown wheat in Ontario belongs to the species Triticum aestivum. As a result of the availability of improved cultivars, local demand and higher returns, there has been renewed interest in durum wheat produc- tion in Ontario. There are a limited number of grass and broadleaved herbicides registered for use in durum wheat in Ontario. Durum wheat has been shown to re- spond differently than conventional wheat to some her- bicides [3,4]. Cultivar differences in the tolerance to some herbicides have been reported within T. aestivum [5-9]. More research is needed to identify herbicide op- tions for durum wheat in Ontario. Dichlorprop plus 2,4-D ester (premix formulated), clopyralid and dicamba/MCPA/mecoprop are phenoxy herbicides that are very effective for the control of a wide spectrum of annual, biennial and perennial broad- leaf weeds including Polygonum lapathifolium (smart- weed), Polygonum convovulus (wild buckwheat), Cap- sella bursa-pastoris (shepherd’s purse), Thlaspi arvense (stinkweed), Lactuca scariola (prickly lettuce) and Tara xacum officinale (dandelion) [10,11]. These are growth regulating herbicides affecting respiration, translocation and cell division [5]. Bromoxynil plus MCPA (premix formulated) is a benzonitrile plus phenoxy herbicide that inhibits photo- synthesis and causes uncontrolled cell division and growth in sensitive weeds [11]. Bromoxynil plus MCPA can