Effect of Xenorhabdus and Photorhabdus bacteria and their exudates on Moniliophthora roreri

Abstract

Frosty pod rot or moniliasis is a very destructive disease of cocoa plantations in Latin America. The conventional methods to control this disease such as the use of chemical pesticides have failed or are too expensive for smallholders. Nowadays, biological alternatives are being investigated to improve yields and to keep moniliasis controlled. Xenorhabdus and Photorhabdus bacteria and their exudates were evaluated against Moniliophthora roreri. All bacteria demonstrated antifungal action reaching up to 97% after 13 days of exposure, whereas some exudates demonstrated more than 70%. Moniliophthora roreri did not sporulate in bacteria presence and sporulation was reduced by their exudates in 70%. The bacteria and exudates were compared with a commercial fungicide used by Venezuelan farmers; better performance of the bacteria and exudates was found and the fungicide was unable to control M. roreri. These experiments showed promising results of Xenorhabdus and Photorhabdus as biocontrol agents for being included in the integrated disease management programmes in Venezuela.

Keywords:

• biological control
• cocoa
• frosty pod
• Theobroma cacao
• entomopathogenic bacteria

Acknowledgements

This project was financially supported by Ministerio del Poder Popular para Ciencias, Tecnología e Innovación de la República Bolivariana de Venezuela under the project number: LOCTI-2011000358. The authors also are grateful to Dr. Simon Gowen and Mrs. Barbara Pembroke for providing us with some of the nematodes species from the University of Reading and Dr. Steve Edgington from CABI for valuable comments and suggestions.