Preparation and application of compound Bacillus sp. water dispersible granules with disease resistance and growth promoting activity

Abstract:

[Background] Common biological agents such as emulsifiable concentrate (EC), wettablepowders (WP), dustpowder (DP) and other biological agents contain benzene and derivatives as organic solvents and dust, which could cause pollution to the environment. Water dispersible granule is considered as one of the most promising dosage forms owing to its environmental friendliness, high added value, and large market potential. However, there are few studies on the compound Bacillus sp. water dispersible granules. [Objective] To prepare a compound water dispersible granule using Bacillus amyloliquefaciens BZ6-1 and Bacillus pumilus SC-12, and evaluate its antimicrobial effects on suppression against bacterial wilt in pepper. [Methods] The effects of different carriers and auxiliaries on the spores of two kinds of Bacillus were investigated in a biocompatibility experiment to select optimal carriers and additives. The effects of different sieve diameter, drying temperature, drying time on the quality of water dispersible granules investigated in a quality inspection experiment to optimize the granulation conditions. Field pepper experiment was conducted by spraying different dosage after planting to field. [Results] The best formula included 4% sodium dodecyl sulfate (wetting agent), 6% sodium carboxymethyl cellulose (dispersant), 4% ammonium sulfate (disintegrating agent), 4% polyethylene glycol (binder), and 82% diatomite (carrier). The optimum conditions for granulation were mesh size 0.8 mm, drying temperature of 40 °C, drying time of 45 min. The optimal water dispersible granule, which meets the national standards for wetting powder, was developed with bacteria content of 2.52×108 cfu/g, suspension rate of 79.3%, pH 6.8, water content of 4.5%, wetting time of 19.6 s, disintegration time of 86.4 s, and moderate particle strength. [Conclusion] Compound Bacillus sp. water dispersible granules effectively controlled pepper bacterial wilt and improved the yield and quality of pepper. The most suitable application rates of as-prepared dispersible granules were recommended to be 3.0 kg/hm2.