Abstract
Baiting tests were conducted to evaluate the effect of increasing Solenopsis invicta virus 3 (SINV-3) dose on fire ant colonies. Actively growing early-stage fire ant (Solenopsis invicta Buren) laboratory colonies were pulse-exposed for 24 hours to six concentrations of SINV-3 (101, 103, 105, 107, 109 genome equivalents/μl) in 1 ml of a 10 % sucrose bait and monitored regularly for two months. SINV-3 concentration had a significant effect on colony health. Brood rating (proportion of brood to worker ants) began to depart from the control group at 19 days for the 109 concentration and 26 days for the 107 concentration. At 60 days, brood rating was significantly lower among colonies treated with 109, 107, and 105 SINV-3 concentrations. The intermediate concentration, 105, appeared to cause a chronic, low-level infection with one colony (n = 9) supporting virus replication. Newly synthesized virus was not detected in any fire ant colonies treated at the 101 concentration, indicating that active infections failed to be established at this level of exposure. The highest bait concentration chosen, 109, appeared most effective from a control aspect; mean colony brood rating at this concentration (1.1 ± 0.9 at the 60 day time point) indicated poor colony health with minimal brood production. No clear relationship was observed between the quantity of plus genome strand detected and brood rating. Conversely, there was a strong relationship between the presence of the replicative genome strand and declining brood rating, which may serve as a predictor of disease severity. Recommendations for field treatment levels to control fire ants with SINV-3 are discussed.



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Acknowledgments
We thank Drs. J. J. Becnel and R. Nagoshi (USDA-ARS, Gainesville, FL) for critical reviews of the manuscript, and C. A. Strong and D. Hall for technical assistance. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the United States Department of Agriculture or the Agricultural Research Service of any product or service to the exclusion of others that may be suitable.
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Valles, S.M., Porter, S.D. Dose response of red imported fire ant colonies to Solenopsis invicta virus 3. Arch Virol 160, 2407–2413 (2015). https://doi.org/10.1007/s00705-015-2520-1
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DOI: https://doi.org/10.1007/s00705-015-2520-1


