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United States Department of Agriculture

Agricultural Research Service

Research Project: Pesticide Application Technologies for Spray-drift Management, Maximizing In-field Deposition, and Targeted Spraying

Location: Crop Production Systems Research Unit

Title: Interaction of Water with Three Granular Biopesticide Formulations

Authors
item Lyn, Margaret
item Burnett, Dan -
item Garcia, Armando -
item Gray, Ron -

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 2009
Publication Date: January 8, 2010
Repository URL: http://hdl.handle.net/10113/41803
Citation: Lyn, M.E., Burnett, D., Garcia, A., Gray, R. 2010. Interaction of Water with Three Granular Biopesticide Formulations. Journal of Agricultural and Food Chemistry, 58(3):1804-1814.

Interpretive Summary: Shelf-life and reliable efficacy are two major requirements that continue to hinder commercialization of numerous biopesticides, pesticides in which a microorganism is used instead of a chemical as an active ingredient. These two formulation characteristics are affected by the amount of unbound or free water available to retard or enable chemical and biological processes. Prior to this study, there had not been any published investigations probing the dynamics of water activity in biopesticide delivery systems as a function of ambient relative humidity. This is of great practical concern since systems are likely to be subjected to fluctuating environmental conditions in real-world applications. The study showed that some delivery systems respond faster or slower to changes in relative humidity relative to others and presents a mechanism by which biopesticide formulations can be engineered to offer better shelf-life and reliable efficacy and a means to effectively increase the possibility of realizing new, renewable pesticide technologies.

Technical Abstract: Two major requirements that continue to hinder commercialization of numerous potential biopesticides are suitable shelf-life and reliable efficacy. Both formulation characteristics are affected by water availability; therefore investigating water-formulation interactions could provide insight into how both properties could be optimized. In the present study, three clay based biopesticides delivery systems, denoted as TRE-G, PEC-G and PESTA, were analyzed using a dynamic vapor sorption analyzer. The objective was to investigate the interaction of water with three different formulations at 25'C and to determine differences in water uptake and water loss kinetics in response to changes in ambient relative humidity over the range from 0 to 90%. All three formulations showed a similar sorption mechanism and no morphological change in response to rehydration. However, the formulations differed in water uptake capacities, rehydration and dehydration kinetics. Water vapor uptake capacity ranged from 5 to 12.5% w/w with TRE-G being the least absorptive and Pesta being the most. The Pesta formulation required 24h to rehydrate from a water activity of 0.10 to 0.70, while PEC-G and TRE-G required 12 and 14h, respectively. The time required for rehydration from a water activity =0.40 to 0.90 ranged from 8 – 32 h. The formulation response time to a decrease in relative humidity from 90 to 70% obeyed the following order: TRE-G < PEC-G < Pesta, with Pesta being the slowest. The implications of the findings as they relate to shelf-life and dew period requirements of biopesticides are discussed.

Last Modified: 7/25/2014
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