METHODS AND RESULTS!

INFLUENCE OF SINV ON INSECTICIDE-TREATED RED IMPORTED FIRE ANT !

Chris M. Powell and Dr. Blake Bextine, Department of Biology, The University of Texas at Tyler, Tyler, Texas 75799!

INSECT COLONIES !> Colonies were collected from the UT Tyler campus, and maintained in the lab (Figure 2). !VIRUS PRESENCE ASSAY!> Presence of virus was verified by extracting total RNA with TRIzol reagent (Invitrogen, CA), the samples were

then amplified by RTPCR using virus specific primers. Presence was assessed by gel electrophoresis (Figure 5).!

VIRUS DELIVERY!> Extracted virus was encapsulated in Sodium alginate pellets delivered to the ants (Bextine et al, 2002).!ADULT INSECTICIDE TOXICITY ASSAYS!> Adult Fire Ants were taken from colonies maintained in the Department of Biology at The University of Texas

at Tyler. Fipronil was purchased from Chem Service Inc. (West Chester, PA) (Figure 6).!> Toxicity was assessed using dip assay. The insect were knocked down on ice for approximately 15 minutes

in a glass plate, and sorted by size. They were then dipped in the compound and placed in a three inch culture plate. Mortality was assessed at 1 hour (Figure 7 and Table 1)!

SUMMARY AND DISCUSSION!> Individuals from virus-positive population responded to higher concentration of Fipronil than virus-negative populations.!> This indicates that Fipronil is an less effective control method in populations infected with SINV, assessment of presence could improve effectiveness of chemical treatments.!> Future study will be focused on the physiological effects of viral infection, in regards to detoxification pathways and immune response by assessing the activity of glutathione s-transferase, general esterase, cytochrome p450, and prophenoloxidase.!> These differences may be used to choose a directed control strategy, exploiting effects of the SINV. !

REFERENCES!1.Bextine, B. R. Thorvilson, H. V. (2002) Field Applications of Bait-Formulated Beauveria bassiana Alginate

Pellets for Biological Control of the Red Imported Fire Ant. Entomological Society of America. Lubbock, Texas.!

2. Drees, B. M., C. L. Barr, D. R. Shanklin, D. K. Pollet, K. Flanders, and B. Sparks. (1999) Managing Red Imported Fire Ant in Agriculture. College Station, TX: Texas Agriculture Extension Services.!

3. Grisham, Julie. (1994) Attack of The Fire Ant. BioScience 44: 587-590!4. *Tufts, D., Hunter, W., and Bextine, B.R. 2009. Discovery of a genetically different form of the Solenopsis

invicta virus (SINV-1) in east Texas. J. Invert Path. 104: 180-185!

ACKNOWLEDGEMENTS!I thank the Office of Sponsored Research at The University of Texas at Tyler for the generous awards to support this research. I thank Danielle Tufts for her previous work with isolation and classification of SINV TX-5, Henry Schreiber and Damon Hall for help troubleshooting molecular procedures, and Dr. Eric Lucas for his work optimizing S. invicta cell culture. Finally I would like to thank Larry LeBeau of the Nature Center – Wildlife Reagion 3 for allowing us to collect ants. This project has been presented at the ESA South Western Branch meeting and the SWAN meeting.!

INTRODUCTION!Solenopsis invicta first appeared in Mobile Alabama in the 1920ʼs; since then, the ants have pushed through out the southern United States, displacing and destroying native species (Drees et al 1999). Multiple chemical, physical, and biological control strategies are currently used to manage the S. invicta; however, cost-effective and effective management tools are still needed. Solenopsis invicta virus (SINV) causes colony collapse. SINV-TX5 can be delivered with efficiently using sodium alginate pellets (Bextine et al, 2002). SINV is specific to the Red Imported Fire Ant, making it a viable resource in the development of species selective control strategies (Tufts et al 2009). Other forms of biological control involve the introduction of a natural predator or parasite, though these species may become invasive in the future. In this study, we determined the feasibility of using common use insecticides in concert with SIN-V to enhance toxicity of current-use insecticides; therefore, reducing the volume of toxic compound needed for effective S. invicta mortality. One common use insecticide was screened; Fipronil is a Phenylpyrazole class insecticide that targets GABA-gated chloride channels causing overstimulation of the neuron, resulting in mortality. !

Figure 6. Molecular structures of Fipronil, a Phenylpyrazole insecticide.!

Figure 3. Amino acid comparison of SINV-1 and SINV-1 (TX5) illustrating 95.5% homology.!

Figure 5. 1% agarose gel of PCR product from SINV screening. !

Table 1. Effective Concentrations (EC) values for Fipronil cause knockdown in 10% (EC10), 20% (EC20), 50% (EC50), and 85% !of individuals.!

Figure 7. Effective concentrations at 10%, 20%, 50%, and 85%. 95% Confidence interval shown by error bars.

ABSTRACT!The Red Imported Fire Ant (Solenopsis invicta Buren) is a tenacious and costly pest to control. Multiple chemical, physical, and biological control strategies are currently being utilized to control the S. invicta; however, cost-effective and effective management tools are still needed. Solenopsis invicta virus (SINV) has been shown to cause colony collapse when other biotic antagonists are present, such as fungal or bacterial pathogens. A divergent strain of SINV-1, which exhibits 95.5% homology specific to Texas (SINV-TX5) has been isolated and extracted. The virus can be delivered efficiently using sodium alginate pellets. Current chemical control strategies are not selective, and indiscriminate use of insecticides can have unintentional environmental effects. SINV is specific to the Red Imported Fire Ant, making it a viable resource in the development of species selective control strategies. In this study, we determined the feasibility of using common-use insecticides in concert with SINV to enhance toxicity of current-use insecticides; therefore, reducing the volume of toxic compound needed for effective S. invicta mortality. !

NTC LNEGITIVE SAMPELS

POSITIVE SAMPELS

500 bp

Figure 1. Progression of sample colonies; yellow represents unknown infection, red represents positive, and blue shows negative. !

Figure 2. Colony members being floated for collection (top). Typical enclosure containing brood box, food source, and water (bottom).!

Figure 4. Phylogenetic tree showing the association of individual viruses within the Dicistroviridae family, accession no. shown in parentheses !

Field Collected Ant Colony!

PCR Screening!

SINV Positive!

SINV Negative!

Virus Extraction!

Colony Split!

Virus Pellets!

Control Pellets!

Toxicity Assay!

Toxicity Assay!

Virus Negative Virus Positive