Paper presented at the 52nd CFCS Annual Meeting, Guadeloupe, July 10-16, 2016 INTEGRATED MANAGEMENT OF DISEASES IN CROP AND ANIMAL PRODUCTION
IN VITRO AND IN VIVO EVALUATION OF CONVENTIONALAND ORGANIC PESTICIDES TO MANAGE FOLIAR DISEASES OF YAM (DIOSCOREA ALATA L.) IN PUERTO RICO Yara Rosado-Rivera, Merari Feliciano-Rivera and Agenol González-Vélez Department of Agro-Environmental Sciences, University of Puerto Rico, Mayagüez Campus, Mayagüez, Puerto Rico Keywords: Yams, anthracnose, fungicides Abstract Yam (Dioscorea alata L.), a member of the Dioscoreaceae family, is one of the most demanded root crops in Puerto Rico. One of the main constraints on yam production are the losses caused by Colletotrichum gloesporioides Penz, the causal agent of anthracnose disease. On susceptible yam cultivars, the disease affects leaves, vines and tubers, resulting in vine dieback, defoliation, and tuber dry rot. Currently in Puerto Rico, Quadris® is the only registered product to manage this disease. The relative lack of research on disease management practices on yam in Puerto Rico is an issue that needs to be addressed to provide more reliable information to local farmers. Thus, the objective of this research was to investigate the potential disease control obtained with OMRI certified materials and conventional fungicides against Colletotrichum spp. in vitro and in vivo. The field research was conducted at the Agricultural Experimental Station of Isabela, Puerto Rico using a randomized complete block design with four replications and ten treatments (Non-treated plants, Quadris®, FontelisTM, Chlorothalonil 720, Trilogy®, Switch® 62.5WG, Kocide® 3000, Kphite® 7LP, and two rates of Regalia®). The same treatments were evaluated in vitro using a colorimetric assay, which uses the absorbance (OD450) of cultures in a microtiter plate to assess mycelial growth. In vitro studies showed that Chlorothalonil 720 and Switch® 62.5WG provided >50% inhibition of mycelial growth of C. alatae and C. gloesporioides at all concentrations tested. In field experiments, the most effective fungicide for managing anthracnose disease and improving the yields of yam was Switch® 62.5WG. None of the OMRI certified materials (Trilogy® and Regalia®) and conventional fungicides provided a significant reduction in disease severity. Given the limited data regarding the efficacy of disease-control products available for yam farmers, our results reported here provide an extensive evaluation of products that may have the potential for managing anthracnose disease in yam.
115