Sterile oat (Avena sterilis L.) cross-resistance profile to ACCase-inhibiting herbicides in Greece Aristeidis P. Papapanagiotou a , Nikolaos S. Kaloumenos b , Ilias G. Eleftherohorinos b, * a Department of Greenhouse Crops and Floriculture, Faculty of Agricultural Technology, Technological Institute of Messolonghi, 302 00 Messolonghi, Greece b Laboratory of Agronomy, School of Agriculture, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece article info Article history: Received 29 March 2011 Received in revised form 12 July 2011 Accepted 2 August 2011 Keywords: Clodinafop-propargyl Diclofop-methyl Fenoxaprop-p-ethyl Imazamox Iodosulfuron methyl-sodium Mesosulfuron-methyl Pinoxaden Tralkoxydim ACCase Herbicide resistance Avena sterilis L. abstract Sterile oat (Avena sterilis) is the most widely distributed, abundant and harmful weed in the winter cereals grown in Greece. Its effective control has relied for the past three decades upon the ACCase- inhibiting herbicides. However, recently many growers in northern and central Greece have experi- enced reduced sterile oat control after the application of fenoxaprop-p-ethyl or clodinafop-propargyl. Preliminary screening indicated that less than 80% of the treated plants in 36 and 43 out of 125 sterile oat accessions were killed (R, resistant) by the application of the four times the recommended dose of fenoxaprop-p-ethyl (R-Fx) or clodinafop-propargyl (ReCd), whereas less than 80% of the treated plants in 29 of them were killed by both herbicides applied at four times the recommended dose. Also, more than 80% of the treated plants in 42 and 35 accessions were killed by the four times the recommended dose (r, partially resistant) of fenoxaprop-p-ethyl (r-Fx) or clodinafop-propargyl (r-Cd), respectively. Finally, more than 80% of the treated plants in 47 and 47 accessions were killed (S, susceptible) by the recommended dose of fenoxaprop-p-ethyl (S-Fx) or clodinafop-propargyl (S-Cd), respectively, whereas more than 80% of the treated plants in 36 of these accessions were killed by the recommended dose of both herbicides. The whole-plant dose-response method used to evaluate 17 R-Fx and five S-Fx accessions showed that 16, 17, 11, and two R-Fx accessions were cross-resistant to clodinafop-propargyl, diclofop-methyl, tral- koxydim, and pinoxaden, respectively. In particular, more than 50% of the treated plants in 12,12,17, and three accessions survived the respective application of the four times the recommended dose of fenoxaprop-p-ethyl, clodinafop-propargyl, diclofop-methyl, and tralkoxydim. Regarding pinoxaden, 3, 17 and 20% of the treated plants in three accessions survived its application at four times the recommended dose. All R and the S accessions were effectively controlled by the recommended dose of imazamox and mesosulfuron-methyl þ iodosulfuron methyl-sodium. These results strongly suggest that cross- resistance to ACCase-inhibiting herbicides has been developed for sterile oat. Therefore, measures should be taken for crop rotation when possible or rotational use of the available ALS- and ACCase- inhibiting herbicides in order to reduce the potential for development of sterile oat multiple resis- tance. Regarding the accessions with cross-resistance to APP, CHD and PPZ, these could be effectively controlled by the application of mesosulfuron-methyl þ iodosulfuron methyl-sodium. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Sterile oat (Avena sterilis L.) is the most important and frequently encountered annual grass weed infesting winter cereals in Greece (Damanakis, 1982). In a recent study (Travlos et al., 2008), sterile oat was observed in 83e91% of the wheat (Triticum aestivum L., T. turgidum L. subsp. durum) fields at the time of crop maturation, whereas wild oat (Avena fatua L.) was found to coexist in small patches and lower densities in 11e 15% of the surveyed fields. Sterile oat is also one of the most widely distributed and abundant weeds in Spain and other Mediterranean environments and causes substantial losses in cereal crops (Gonzales-Andujar et al., 2010). Estimated yield losses of wheat caused by sterile oat infestations range between 17% and 62% (Balyan et al., 1991), whereas yield reduction in barley (Hordeum vulgare L.) varies between 8% and 67% (Dhima et al., 2000). According to Kadioglou et al. (1998), sterile oat is very competitive and the economic threshold is four wild oat plants m 2 . Effective sterile and wild oat control in winter cereal crops grown worldwide relies upon the selective post-emergence applied herbicides, which belong to aryloxyphenoxypropionates (APPs), * Corresponding author. Tel.: þ30 2310998629. E-mail address: eleftero@agro.auth.gr (I.G. Eleftherohorinos). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro 0261-2194/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2011.08.001 Crop Protection xxx (2011) 1e9 Please cite this article in press as: Papapanagiotou, A.P., et al., Sterile oat (Avena sterilis L.) cross-resistance profile to ACCase-inhibiting herbicides in Greece, Crop Protection (2011), doi:10.1016/j.cropro.2011.08.001