Send Orders of Reprints at reprints@benthamscience.net 24 The Open Plant Science Journal, 2013, 7, 24-30 1874-2947/13 2013 Bentham Open Open Access Weed Control in White Bean with Pendimethalin Applied Preplant Followed by Postemergence Broadleaved Herbicides N. Soltani* ,1 , R.E. Nurse 2 , C. Shropshire 1 and P.H. Sikkema 1 1 University of Guelph Ridgetown Campus, Ridgetown, Ontario, Canada, N0P 2C0; 2 Agriculture and Agri-Food Canada, Harrow, Ontario, Canada, N0R 1G0 Abstract: Field trials were conducted over a three-year period (2009 to 2011) to evaluate the efficacy of pendimethalin preplant-incorporated (PPI), bentazon, fomesafen, bentazon plus fomesafen, or halosulfuron applied postemergence (POST) and the sequential application of pendimethalin applied PPI followed by bentazon, fomesafen, bentazon plus fo- mesafen or halosulfuron applied POST in white bean in Ontario. There was minimal effect on seed moisture content of white bean with the herbicides evaluated. Pendimethalin provided 97% control of A. retroflexus, 9% of A. artemisiifolia, 90% of C. album, 12% of S. arvensis, and 96% of S.viridis. Bentazon, fomesafen, bentazon plus fomesafen, and halosul- furon applied POST provided as much as 93% control of A. retroflexus, 86% control of A. artemisiifolia, 72% control of C. album, 99% control of S. arvensis, and 29% control of S. viridis. The sequential application of pendimethalin applied PPI followed by bentazon, fomesafen, bentazon plus fomesafen, and halosulfuron applied POST provided 100% control of A. retroflexus, 87% control of A. artemisiifolia, 90% control of C. album, 100% control of S. arvensis, and 95% control of S .viridis, respectively. White bean yield generally reflected the level of weed control. Keywords: Bentazon; density; dry weight; fomesafen; halosulfuron; navy bean; pendimethalin; yield INTRODUCTION Canada is one of the largest white bean (Phaseolus vul- garis L.) producing countries in the world [1]. In 2010, On- tario growers produced 82,600 MT of white bean with a farm-gate value of $55 million on 34,400 hectares [2]. White bean is a short season crop with short physical stature and is not a strong competitor with weeds. Weed interference can result in as much as 70% yield losses in white bean [3,4]. Weeds also interfere with harvest operations and may stain white bean, resulting in reduced market value [5-7]. Therefore weed management is very important for profitable white bean production. Identification of weed management strategies that provide consistent effective broad spectrum weed control is needed to make white bean growers competi- tive in the global market. Pendimethalin is a dinitroaniline herbicide that controls annual grasses including barnyardgrass (Echinochloa crus- galli (L.) Beauv.), smooth crabgrass (Digitaria ischaemum (Schreb) Muhl.), large crabgrass (Digitaria sanguinalis (L.) Scop), fall panicum (Panicum dichotomiflorum Michx., giant foxtail (Setaria faberii Herrm.), S. viridis, and yellow foxtail (Setaria glauca (L.) Beauv.). Pendimethalin can also control certain annual broadleaved weeds such as common lamb’s- quarters (Chenopodium album L.) and redroot pigweed (Amaranthus retroflexus L.) including acetolactate synthase and triazine-resistant biotypes [8,9]. *Address correspondence to this author at the University of Guelph Ridge- town Campus, Ridgetown, Ontario, N0P 2C0, Canada; Tel: 519-674-1500; Fax: 519-674-1600; E-mail: soltanin@uoguelph.c Bentazon is a benzothiadiazole postemergence (POST) herbicide that can control broadleaved weeds including Che- nopodium album, purslane (Portulaca oleracea L.), wild radish (Raphanus raphanistrum), hairy galinsoga (Galinsoga ciliata), common groundsel (Senecio vulgaris), jimsonweed (Datura stramonium L.), velvetleaf (Abutilon theophrasti Medic.), ladysthumb (Polygonum persicaria L.), wild mus- tard (Sinapis arvensis L.), cocklebur (Xanthium strumarium L.), shepherdspurse (Capsella bursa-pastoris) and common chickweed (Stellaria media) including acetolactate synthase and triazine-resistant biotypes [8,9]. Fomesafen is a diphenyl ether herbicide that can control broadleaved weeds such as Sinapis arvensis, Amaranthus retroflexus, Ambrosia artemisiifolia, Polygonum persicaria, Xanthium strumarium and Solanum spp. [8,9]. Fomesafen in tank mix combination with bentazon can provide improved control of broadleaved weeds such as Amaranthus, Ambro- sia, Solanum and Polygonum convolvulus [8,9]. Halosulfuron is a sulfonylurea herbicide that controls several broadleaved weeds that occur in Ontario such as Amaranthus retroflexus, Abutilon theophrasti, Polygonum persicaria, Xanthium strumarium, Sinapis arvensis, and nut- sedge species (Cyperus spp.), including triazine resistant biotypes [9]. Combination of graminicide herbicides with broadleaved herbicides has been shown to improve the level of weed con- trol in dry bean [10]. However, there is little information on the relative efficacy of pendimethalin applied PPI followed by POST herbicides such as bentazon, fomesafen, bentazon plus fomesafen or halosulfuron in white bean under Ontario environmental conditions.