Identification and control of pathogenic fungi in neotropical valued orchids (Laelia spp.)

Laelia species are valued orchids for ornamental and ritual uses. Since their natural populations are at risk, a suitable alternative is cultivation. However, the fungi affecting orchid cultivars are largely unknown. In this study, pathogenic fungi of Laelia autumnalis, L. rubescens, and L. speciosa in cultures of Morelia city orchid collections were identified using molecular and morphological methods. Pathogenicity tests were conducted using in vitro L. speciosa seedlings and a bioassay with three fungicides. Thirty-nine strains belonging to 10 taxa were isolated: Aspergillus fumigatus, Colletotrichum boninense, C. karstii, Fusarium bactridioides, F. oxysporum, F. proliferatum, F. solani, Fusarium sp., Xylaria feejeensis, and an Ascomycete strain. The most common pathogens in adult plants were F. proliferatum and A. fumigatus . The most aggressive fungus was F. solani . The Ascomycete, A. fumigatus and X. feejeensis, are reported herein as opportunistic orchid pathogens for the first time under in vitro conditions. The fungicide thiabendazole significantly inhibited the growth of F. proliferatum and F. solani , while benomyl inhibited the growth of A. fumigatus and F. bactridioides after five days. All tested fungicides did not inhibit the growth of C. boninense, F. oxysporum, Fusarium sp ., and the Ascomycete strain. Our results will be useful to improve management recommendations for these endangered orchid species.