Insecticidal Properties and Microbial Contaminants in a Spodoptera exigua Multiple Nucleopolyhedrovirus (Baculoviridae) Formulation Stored at Different Temperatures
Authors: Lasa, Rodrigo; Williams, Trevor; Caballero, Primitivo
Source: Journal of Economic Entomology, Volume 101, Number 1, February 2008 , pp. 42-49(8)
Publisher: Entomological Society of America
Abstract:The Spodoptera exigua (Hübner) multiple nucleopolyhedrovirus (SeMNPV) is currently being tested as a biological insecticide for use in greenhouse crops in southern Spain. We performed a study in which semipurified SeMNPV occlusion bodies (OBs) were formulated in phosphate-buffered saline, pH 6.5, with 5% (vol:vol) glycerol and 0.15% (wt:vol) sorbic acid, and they were stored at −20, 4, or 25°C during 18 mo. Initial aerobic counts (±SE) averaged 1.4 (±0.17) × 107 colony-forming units/ml after 17-h incubation at 37°C. Aerobic counts of microorganisms that contaminated OB formulations stored at 25°C decreased markedly over the period of the study, whereas only small decreases were observed in counts from OBs stored at 4 or −20°C. The principal microbial contaminants of OB suspensions were Enterococcus spp., Enterobacteriaceae, and yeasts. Potential human pathogens (Salmonella, Shigella, and Vibrio species) were not detected, and populations of Staphylococcus aureus and Bacillus cereus were extremely low. Compared with newly formulated OBs, the estimated LD50 values of OBs stored at 25°C increased by >16,666-fold over the 18 mo of storage, whereas LD50 values were not greatly affected by storage at 4 or −20°C. Significant changes over time in OB concentrations were only observed in the 25°C treatment. Complete degradation of viral DNA was observed at 25°C but not in refrigerated or frozen OBs. We conclude that OB formulation with bacteriostatic or antioxidant additives, together with storage and distribution in refrigerated conditions, will likely result in an SeMNPV biopesticide shelf life that exceeds 18 mo.
Document Type: Research Article
Publication date: February 2008
- Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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