Preparation of Spray-Dried Wettable Powder Formulations of Bacillus thuringiensis-Based Biopesticides

Authors: Teera-Arunsiri, Aroonrat; Suphantharika, Manop; Ketunuti, Uthai

Source: Journal of Economic Entomology, Volume 96, Number 2, April 2003 , pp. 292-299(8)

Publisher: Entomological Society of America

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Abstract:

Bacillus thuringiensis is the most widely used biopesticide among many methods available to control insects. To make a saleable product, B. thuringiensis must be substantially concentrated by removal of water and formulated to improve longevity, efficacy, and ease of transport of the product. B. thuringiensis subsp. aizawai culture broth as an active ingredient was mixed with various adjuvants and then spray dried. The optimum conditions for spray drying were found to be an outlet temperature of 60–85°C and an inlet temperature of 120–180°C. Various adjuvants had different effects on physical and biological properties of the dried product. Gelatinized tapioca starch and milk powder improved suspensibility but adversely affected wettability of the dried formulated product. Vegetable oil and Tween 20 enhanced wettability but resulted in poor suspensibility. Silica fume was used to enhance flowability because it reduced clumping and caking of the powder resulting from the addition of vegetable oil. Formulation containing 10% wt:wt B. thuringiensis, 10% wt:wt gelatinized tapioca starch, 10% wt:wt sucrose, 38% wt:wt tapioca starch, 20% wt:wt milk powder, 10% wt:wt silica fume, 2% wt:wt polyvinyl alcohol, 5% vol:vol Tween 20, 1% vol:vol refined rice bran oil, and 1% vol:vol antifoam solution was found to be optimum in terms of the physical and biological properties of the dried product. This formulation had 55% suspensibility, 24 s for wetting time, and 5.69 × 104 CFU/ml of LC50 value against Spodoptera exigua larvae.

Keywords: B. thuringiensis; biopesticides; formulation; spray drying; suspensibility; wettability

Document Type: Research Article

DOI: http://dx.doi.org/10.1603/0022-0493-96.2.292

Publication date: April 1, 2003

More about this publication?
  • Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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