In vitro evaluation of antagonistic microorganisms and fungicides against Colletotrichum theobromicola Delacr, causal agent of anthracnose on soursop (Annona muricata L.) inflorescences

The objective of this study was to evaluate the in vitro antagonism of six strains of microorganisms on Colletotrichum theobromicola Delacr, the causal agent of anthracnose in soursop (Annona muricata L.) inflorescences in Nayarit, Mexico. Three strains of Trichoderma (T asperellum, T harzianum and T. longibrachiatum), three strains of Streptomyces [Streptomyces sp. (A7), S. tubercidicus (A19), and S. viridochromogenes (A27)] and seven commercial fungicides Maxtrobyn (R) (azoxystrobin SC), ExCitrus (R) (Citric extract + quercetin), Canelys (R) (Cinnamomum zeylanicum extract), Hidrocu (R)) PH (Copper hydroxide), Pull75WG (R) (cuprous oxide), Score (R) 250 EC (Difenoconazole) and Switch (R) 62.5 WG (cyprodinil + fludioxonil) were used. The fungicides doses were: D1 (half of the recommended dose), D2 (recommended dose), and D3 (recommended dose plus half of it), according to the doses recommended by the manufacturer. The six antagonists showed more than 80 % of radial growth inhibition, the genus Streptomyces was the most efficient inhibiting up to a 90 % the growth of C. theobromicola. Strain A27 completely inhibited the fungi (100 %), followed by strains A19 (96.18 %) and A7 (90.4 %). SCORE (R) 250 EC, Canelys (R) and Hidrocu (R) PH fungicides showed a 100 % in vitro inhibition of C. theobromicola with the three doses analyzed. The results of this study demonstrate the potential of Streptomyces spp. strains and commercial fungicides for the control of C. theobromicola, which can be further used in the integrated management for controlling anthracnose in soursop.