Influence of formulation additives on the desiccation tolerance and storage stability of blastospores of the entomopathogenic fungus Paecilomyces fumosoroseus (Deuteromycotina: Hyphomycetes)

Abstract

Blastospores of the entomopathogenic fungus Paecilomyces fumosoroseus were formulated with 10% lactose/1% bovine serum albumin (BSA) or various compositions of Fantesk™, a starch–oil composite prepared by jet-cooking an aqueous dispersion of starch and oil. Storage stability studies with wet blastospore formulations showed that maximum blastospore survival was achieved during low-temperature storage at −20°C with lactose/BSA formulations or starch–oil formulations supplemented with sucrose, zein protein, and whole milk. Under conditions of wet storage at −20°C, the addition of whole milk to starch–oil formulations significantly improved blastospore stability while the addition of sucrose or zein protein had no effect. In freeze-drying studies, no significant differences were seen in blastospore desiccation tolerance or in stability during storage at either 4 or −20°C when blastospores of P. fumosoroseus were formulated with lactose/BSA or starch–oil formulations with sucrose, zein protein, and whole milk. Freeze-dried blastospore formulations stored at 4°C showed no loss in blastospore viability after 3 months storage and blastospore formulations stored at −20°C showed no loss in viability during the entire 12-month study. For freeze-dried, starch–oil formulations, sucrose was shown to improve blastospore survival during the freeze-drying process. The addition of whole milk to starch–oil formulations significantly improved the stability of freeze-dried blastospores stored at 4°C. Compared to unformulated blastospore suspensions that showed blastospore settling after 30 min, suspensions of blastospores formulated with lactose/BSA or starch–oil composites remained stable for up to 2 h after mixing.

Keywords:

• Paecilomyces fumosoroseus
• blastospores
• formulation
• Fantesk™
• storage stability
• fermentation
• bioinsecticide
• biocontrol

¹ The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned.

¹ The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned.

Acknowledgments

The authors express their gratitude to Angela Payne and Connie Vealand for their excellent technical assistance throughout this study. We also thank Stephen Wraight for his generous assistance in the analysis of the insect mortality data after the passing of Tad Poprawski and Debra Palmquist for her guidance in the statistical analysis of data.

Notes

¹ The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned.

Additional information

Notes on contributors

Selim Erhan*

* Present address: Georgia-Pacific Corporation, Bedford Park, IL, USA

Tadeusz J. Poprawski†

† Deceased