Bull. Spec. CORESTA Congress, Lisbon, 2000, p. 60, AP10
Bacillus thuringiensis as a candidate for the biocontrol of stored tobacco insect pests
Philip Morris Europe, R&D, Neuchatel, Switzerland.
The cigarette beetle, Lasioderma serricorne (F.) and the tobacco moth, Ephestia elutella (Hübner) are the major insect pests of both raw and manufactured tobacco. Post-harvest tobacco control is achieved through sanitation, insect monitoring, and fumigation with phosphine. However, insect resistance to phosphine and control failures have been recently reported, and increasing regulatory pressure is being exerted on fumigants. The integration of conventional control approaches with novel systems based on biological agents with different modes of action should offer new avenues of effective management of stored tobacco pests.The objective of our study was the evaluation of the activity of the soil bacterium Bacillus thuringiensis (Bt), the most widely used biocontrol agent worldwide, on the cigarette beetle. Bt produces insecticidal crystal proteins that become active upon ingestion and are specific for certain orders of insects. Our laboratory has conducted extensive research and worldwide surveys to evaluate the presence of Bt in stored tobacco and has confirmed previous findings indicating that Bt may be considered part of the naturally occurring phylloplane microflora. Several Bt strains were isolated from tobacco and characterized by DNA and protein profiling. The insecticidal activity of selected strains and two commercial products against the larvae of L. serricorne was determined by diet incorporation assays. Moreover, the stability of Bt spores and crystal proteins on cured tobacco leaves was assessed over a storage period of time of 30 months. The experimental results indicated that Bt has potential for the control of the cigarette beetle, although the tested strains and products did not yield satisfactory levels of mortality at the required times and doses. Cigarette prototypes were made with Bt-treated tobacco. Standard cigarette and smoke evaluation did not show any significant difference compared with the control cigarette.