Crop Protection 140 (2021) 105403 Available online 28 September 2020 0261-2194/© 2020 Elsevier Ltd. All rights reserved. Effcacy of fungicides against peanut smut in Argentina J.A. Paredes a, * , L.I. Caz´ on a, e , C. Oddino b , J.H. Monguillot a , A.M. Rago b, c , J.P. Edwards Molina d a Instituto de Patología Vegetal, UFYMA, CIAP - INTA, C´ ordoba, Argentina b Facultad de Agronomía y Veterinaria, IMICO, UNRC, C´ ordoba, Argentina c Centro de Investigaciones Agropecuarias - INTA, C´ ordoba, Argentina d Estaci´ on Experimental Agropecuaria - INTA, Balcarce, Argentina e Departamento de Fitopatologia, Universidade Federal de Viçosa, MG, Brazil A R T I C L E INFO Keywords: Thecaphora frezii Chemical control In vitro sensitivity Peanut disease Active ingredients ABSTRACT Peanut smut, caused by Thecaphora frezii, increased its incidence and prevalence in the main growing region of Argentina in the last decade becoming the main peanut disease. Despite this fact, growers continue producing peanut without any disease management strategy, which is leading to a local accumulation of T. frezii inoculum. The goal of the present study was to assess the effcacy of 12 fungicides in controlling T. frezii. For this purpose, in vitro assays, pot, and feld experiments were performed during 2014/15 and 2015/16. In vitro assays classifed the fungicides regarding their capacity to inhibit T. frezii mycelium growth as: thiophanate-methyl – not fun- gitoxic (EC50 > 100); mancozeb – moderately fungitoxic (EC50 = 6.28); difenoconazole, propiconazole, cyproconazole, tebuconazole, picoxystrobin, azoxystrobin, kresoxim-methyl, pyraclostrobin, penthiopyrad, and chlorothalonil – highly fungitoxic (EC50 < 0.1). Azoxystrobin showed the highest control levels in pot experi- ments: 58.9% (2014/15) and 92% (2015/16). The greatest control effciency in feld experiments was observed for cyproconazole in 2015 and azoxystrobin in 2016, reducing peanut smut by 47.7% and 39.5%, respectively. Based on our results, chemical control can be considered as a moderately effcient practice which may com- plement the cultivar genetic resistance and cultural practices in an integrated approach for managing peanut smut. 1. Introduction Peanut (Arachis hypogaea L.) is an important crop that is cultivated worldwide, with its center of origin in northwestern Argentina and southeastern Bolivia (Hammons et al., 2016). Argentina produces a high-quality peanut in an area of 350,000 has, concentrating more than 90% in the province of C´ ordoba located at the center region of the country. More than 95% of peanut production is exported and was previously processed in situ by the industry established in the same growing region (Agüero, 2017; Calzada and Rozadilla, 2018). Peanut smut, caused by the soil-borne fungi Thecaphora frezii Car- ranza and Lindquist, is an endemic and yield reducing disease for the main Argentine growing region (Marinelli et al., 2008, 2010; Rago et al., 2014). The pathogen is a biotrophic fungus that produces sori consisting of a powdery mass of teliospores which colonize the seed tissue partially or totally, with potential total damage of the plant pods (Astiz Gasso et al., 2008). The infection process occurs during the crop pegging stage, when fower gynophores penetrate the soil surfaceand their exudate stimulates spore germination (Marinelli et al., 2008). Currently, no management strategies for reducing T. frezii infections are adopted by Argentine growers, which is leading to inter-annual inoculum accumulation (Paredes et al., 2017). Granoleico peanut cultivar (highly susceptibility to the smut) is planted in more than 80% of the growing region (Caz´ on et al., 2018; Cignetti et al., 2010; Rago et al., 2017). Breeding programs with the aim of incorporating wild resistance genes have recently been initiated (Bressano et al., 2019). However, the simplifed peanut local system production, promoted by industry, pretends to adopt a single cultivar massively, and any intention of including new cultivars may be diffcult in the short term. Smut spores are survival structure which can remain viable for new infections up to four years (Caz´ on et al., 2016a) which implies that a short peanut crop rotation is an ineffcient practice to reduce disease * Corresponding author. Instituto de Patología Vegetal – IPAVE; Centro de Investigaciones Agropecuarias – CIAP, Av. 11 de Septiembre 4755, X5020ICA, C´ ordoba, Argentina. E-mail address: paredes.juanandres@inta.gob.ar (J.A. Paredes). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro https://doi.org/10.1016/j.cropro.2020.105403 Received 19 May 2020; Received in revised form 21 September 2020; Accepted 22 September 2020