Efficiency of Bacillus thuringiensis subsp. kurstaki in crude solid fermented matter against the coconut pest, Aceria guerreronis
Robinson Babysarojam Smitha1
1 Enzyme Technology Laboratory, Biotechnology Division, Department of Botany, University of Calicut, Kerala - 673 635, India
2 Acarology Division, Department of Zoology, University of Calicut, Kerala - 673 635, India
Bt Research, 2015, Vol. 6, No. 2 doi: 10.5376/bt.2015.06.0002
Received: 14 Dec., 2014 Accepted: 23 Feb., 2015 Published: 05 Mar., 2015
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The coconut palm appears to be virtually the only host of coconut mite, Aceria guerreronis Keifer. This serious and exponentially multiplying mite has not succumbed to any control treatments yet, due to its microscopic structure and cryptic life. For the first time, it was explored whether Bacillus thuringiensis subsp. kurstaki (Btk) could be used as an efficient bio-control agent to combat this mite. In a biphasic fermentation strategy for the overproduction of δ-endotoxin, the conventional Luria-Bertani (LB) medium was supplemented with 10% (w/v) potato flour. After initial submerged fermentation of this modified medium for 12 h, the wet and crude solid pellet (i.e., without free solution) with Btk embedded in it was incubated further up to 48 h under solid-state fermentation for obtaining crude fermented matter. A bio-assay set-up was standardized for A. guerreronis on tender coconut button. The probit value (lethal dose) of solid-fermented matter (obtained from potato flour supplemented LB) was 1.64 µg/cm2 with 18 folds more efficiency than the LB control. Preliminary field trial showed that one time application of crude solid-fermented matter in the leaf pockets of the infested coconut palms - prior to monsoon - could be efficient to combat the mite permanently, if all palms in a plantation receive a simultaneous treatment.
Aceria guerreronis; Bacillus thuringiensis; mite, solid-state fermentation; δ-endotoxin; pest biocontrol