Isolation and Preliminary Evaluation of Mycoparasites as Biocontrol Agents of Crown Rot of Banana

Thirty mycoparasites were detected using plates precolonized with pathogens of the crown-rot disease complex:Colletotrichum musae(6 strains),Fusarium moniliformevar.subglutinans(2 strains),F. moniliforme,Fusarium pallidoroseum, Botryodiplodia theobromae, andNigrospora sphaerica(1 strain each). Dry leaves, dry flower residues, green leaves, and green peel were compared as mycoparasite sources. Dry leaves were the most prolific source, whereas green material collected in the canopy yielded the least number of isolates. Host species differed significantly in their suitability as bait for mycoparasites.C. musaewas the best host for the isolation of most mycoparasites; fusaria were least colonized. No difference between strains of the same host species was detected during isolation. In contrast, in dual culture, differentC. musaestrains exhibited significant differences in susceptibility to mycoparasitism. The consequence of this finding for practical biocontrol is discussed. Thirteen aggressive antagonists, includingPythiumsp.,Trichodermasp.,Gliocladiumsp., andVerticilliumsp., were selected for further evaluation. Preliminary efficacy, host range, aggressiveness against survival structures (conidia and haustoria), and tolerance to fungicides presently used for crown-rot control were investigated. Eight mycoparasites had a reasonable number of desirable traits, but no single strain exhibited all features required for consistent biocontrol. It is suggested that future studies should consider combining two or three strains and/or to apply them with a reduced rate of a fungicide combined into the inoculum.