TY - JOUR AU - Rosa-Márquez, Evelyn AU - Rivera, Lydia I. AU - Ortiz, Carlos E. AU - Rodríguez, Arcángel PY - 2000/04/01 Y2 - 2024/03/28 TI - Fungi pathogenic to the corm of arracacha (Arracada xanthorrhiza) in Puerto Rico JF - The Journal of Agriculture of the University of Puerto Rico JA - JAUPR VL - 84 IS - 1-2 SE - Articles DO - 10.46429/jaupr.v84i1-2.3901 UR - https://revistas.upr.edu/index.php/jaupr/article/view/3901 SP - 53-64 AB - <em>Phytophthora palmivora</em>, <em>Rhizoctonia</em> sp. and two isolates of <em>Fusarium</em> spp. were identified and associated with the arracacha (<em>Arracada xanthorrhiza)</em> corm rot in pathogenicity tests conducted in vitro and in vivo. In vitro tests revealed that these fungi were pathogenic to the corm. Fungi caused lesions to the corm under greenhouse conditions. Three major symptoms were observed: necrotized roots; necrotized roots with a dry, brown, hard injury to the internal corm tissue; and wet lesions with brown shades. The highest incidence of affected corms occurred with <em>P. palmivora</em> in combination with <em>Rhizoctonia</em> sp., and the lowest was observed in corms inoculated with <em>Rhizoctonia</em> sp. alone. The most severe symptoms were caused by <em>P. palmivora</em> alone and in combination with <em>Rhizoctonia</em> sp. In vitro tests were conducted to evaluate the efficacy of metalaxyl, etridiazofe thiophanate-methyl, and fosetyl-al against the isolated fungi at doses of 5 to 200 mg ai/kg. Among the fungicides tested, etridiazole thiophanate-methyl was effective against all fungi associated with corm rot. Micelial growth of <em>P. palmivora</em> was completely inhibited with metataxyl at all doses and by etridiazole thiophanate-methyl with doses of 20 or more mg ai/kg. ER -