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New Zealand Plant Protection 63 (2010): 284

Preformulation characterisation of zeolite core materials in biocontrol products

C.R. Bunt, S.A. Stelting, D.A. Wright and J. Swaminathan


Bioshield™ is a unique biocontrol agent that is used for control of the New Zealand grass grub (Costelytra zealandica). It consists of a core of zeolite with a biopolymer coating containing the bacterium Serratia entomophila. Assessments of various zeolites (Z1-BC, Z1-BDW, Z1-CG and Z1-BI from New Zealand (NZZs) and AU-FM 4/1 and AU-ZB from Australia (AZs)) were carried out prior to formulation. Physical characteristics, such as friability and water absorption and sorption, were measured and success of bacterial coating was assessed by light microscopy and differential staining, scanning electron microscopy (SEM) and cell loading (cfu/g). Friability assessment of NZZs found approximately 5% mass loss while AZs did not lose any mass. NZZs absorbed approximately 30% w / w while AZs 10% w / w water. Water sorption to zeolites appeared to monolayer in nature, although NZZs and AZs monolayer adsorption isotherms appear to differ, being type II and type I respectively. SEM analysis showed the surface of NZZs to be porous and populated by colloidal particles while AZs appeared very smooth and lacking in surface features. Success of coating S. entomophila onto NZZs and AZs was confirmed by SEM, enumeration and live-dead staining.

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