Effect of Plant Type on the Persistence of Beauveria bassiana

Abstract

Field evaluation of isolate MK 2001 of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin, revealed conidia persistence and infectivity up to 26 days on foliage of lettuce and celery, two crops with substantial plant differences. Plants were treated at a rate of 100 ml/cage at a concentration of 1×10⁸ conidia/ml. The number of colony-forming units (CFU) recovered immediately after treatments from discs sampled on lettuce and celery leaves were not significantly different, due to similar foliar coverage of conidia by application. Significant differences were observed between both host plants during the 26 days of the field trial. The number of CFUs recovered on lettuce was significantly higher than that on celery leaves. However, for each host plant, there were no significant differences either between lettuce external leaves and internal leaves or between celery canopy and bottom leaves. An in vitro pathogenicity test carried out on Lygus lineolaris adults fed with leaf discs harvested from treated cages resulted in a high pathogenicity of B. bassiana isolate MK 2001. The mortality immediately after treatment did not differ from the death counts taken every other day for 26 days. However, efficacy was significantly different between both plants. Mortality was 91% on lettuce and 78% on celery, 7 days post-treatment. This study highlighted that plant type must be taken into account in foliar application of B. bassiana.

Keywords:

• entomopathogenic fungus
• Beauveria bassiana
• pathogenicity
• biological control
• lettuce
• celery
• persistence
• plant type

Acknowledgments

We thank the Ivory Coast Government (Société Autonome des Bourses de Côte d'Ivoire), the UQAM Foundation, and the Conseil des Recherches en Pêcherie et en Agro-Alimentaire du Québec for financial support of this research. We also thank Prisme (Quebec Pest Monitoring) and Mr. Patrick van Widden for providing field plots and students Misha Price, Eve Catherine, Nicolas Legault, and Valerie Nkovet for technical assistance.