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United States Department of Agriculture

Agricultural Research Service

Research Project: IPM-BASED STRATEGIES FOR INCORPORATING MICROBIAL BIOLOGICAL CONTROL FOR MANAGEMENT OF GREENHOUSE AND NURSERY CROP PESTS

Location: Biological Integrated Pest Management Unit

Title: Application of modified atmosphere packaging (gas flushing and active packaging) for extending the shelf life of Beauveria bassiana conidia at high temperatures

Authors
item Faria, Marcos -
item Hotchkiss, Joseph -
item Wraight, Stephen

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 16, 2011
Publication Date: December 24, 2011
Citation: Faria, M., Hotchkiss, J.H., Wraight, S.P. 2011. Application of modified atmosphere packaging (gas flushing and active packaging) for extending the shelf life of Beauveria bassiana conidia at high temperatures. Biological Control. 61:78-88.

Interpretive Summary: Limited shelf life has long been a major constraint to the development of fungus-based bioinsecticides (mycoinsecticides). Fungal spores comprising the active ingredients of most products typically lose viability within a few months when stored in conventional packaging at temperatures above 85 deg F (30 deg C). Methods for improved survival at high temperatures are greatly needed, as pesticides may be exposed to extreme conditions for extended periods during transport, warehousing, or on-farm storage, especially in the tropics or subtropics. In this study, we investigated the potential for use of commercially available moisture- and/or oxygen-absorbing sachets to increase the high-temperature shelf lives of spore powders of the common insect biocontrol fungus Beauveria bassiana. Maximum longevity was observed when spores were stored in airtight packages (aluminum-lined plastic bags) with sachets that absorbed both moisture and oxygen. Spores stored at 104 deg F (40 deg C) for 16 months retained approximately 70 percent viability, spores stored at 122 deg F (50 deg C) for 3 months remained 65 percent viable. To our knowledge, these are the longest high-temperature survival times yet recorded for B. bassiana spore powders. Technologies that improve shelf life of insect pathogenic fungi ensure that pest managers receive high-quality products, which translates to greater commercial development potential for these microbial biocontrol agents.

Technical Abstract: Limited shelf life has long been a major constraint to the development of fungus-based bioinsecticides (mycoinsecticides). Fungal spores comprising the active ingredients of most products typically lose viability within a few months when stored in conventional packaging at temperatures >30 deg C. Methods for improved survival at high temperatures are greatly needed, as pesticides may be exposed to extreme conditions for extended periods during transport, warehousing, or on-farm storage, especially in the tropics or subtropics. In this study, we investigated effects of modified-atmosphere packaging (MAP) on longevity of conidia of Beauveria bassiana (Bb) strain GHA. Similar rates of conidial survival (49–51% viability) were observed after 60 days of storage at 50 deg C in atmospheres of pure CO2, N2, H2, or He, but few conidia (=2%) survived storage in O2-rich atmospheres. Viability of conidia stored in an atmosphere of 20% CO2/80% N2 decreased to <80% within 180 days at 40 deg C and within 30 days at 50 deg C but remained high (87%) after a 16-month storage period at 25 deg C. Residual O2 in the storage containers ranged from 0.3% at the start to as high as 12.4% at the end of the experiments. When active packaging (hermetically sealed packages with O2/moisture scavengers) was employed, shelf lives increased substantially. Viabilities in the 80-89% range were consistently recorded after six months at 40 deg C or 2 months at 50 deg C when a dual O2/moisture absorber or a combination of sachets (dual O2absorber/CO2generator + desiccant) were used. Most favorable water activities (aw) were = 0.030, suggesting that optimal aw for long-term storage under anaerobic conditions is lower than determined in previous studies of storage in the presence of O2. Additionally, we have shown that actively packaged conidia with higher than desirable initial aw should be allowed an equilibration period at a moderate temperature before exposure to high ambient temperatures. Active packaging of dried conidia (aw = 0.032) preserved ca. 70% viability for 16 months at 40 deg C, and close to 65% for 3 months at 50 deg C. To our knowledge, these are the longest survival times yet reported for Bb conidia under high-temperature conditions.

Last Modified: 10/1/2014
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