Mark A. Brinkman

A survey of ground-dwelling ants (Hymenoptera: Formicidae) in Georgia

Abstract Ground-dwelling ants (Hymenoptera: Formicidae) were sampled at 29 sites in 26 counties in Georgia with pitfall traps, leaf litter extraction, visual searching, and bait stations. We found 96 ant taxa including nine species not previously reported from Georgia: Myrmica americana Weber, M. pinetorum Wheeler, M. punctiventris Roger, M. spatulata Smith, Pyramica wrayi (Brown), Stenamma brevicorne (Mayr), S. diecki Emery, S. impar Forel, and S. schmitti Wheeler, as well as three apparently undescribed species (Myrmica sp. and two Stenamma spp.). Combined with previous published records and museum records, we increased the total number of ground-dwelling ants known from Georgia to 144 taxa.

Distribution of the fire ant (Hymenoptera: Formicidae) hybrid in Georgia.

The red imported fire ant, Solenopsis invicta Buren, and the black imported fire ant, S. richteri Forel, are reproductively isolated in their native South America even where their ranges overlap (Ross and Shoemaker 2005, Mol. Ecol. 14: 3,419-38). Yet, these invasive ant species readily hybridize in their expanded ranges in North America. Vander Meer and Lofgren (1988, Florida Entomol. 71: 232-32) determined that hybridization occurred in south Alabama soon after the invasion of these ant species. Hybrid ants are morphologically similar to S. richteri and S. invicta, and chemical analysis of ant venom and cuticular hydrocarbons or genetic characterization are required to distinguish hybrid ants from the parent species (Vander Meer et al. 1985, Florida Entomol. 68: 501-06; Ross et al. 1987, Evol. 41: 280-93). Drees et al. (2006, Texas Coop. Ext. B-6043) recently showed S. richteri distributed in only 8 counties in northern Mississippi and 10 counties in west central Tennessee. The S. richteri x S. invicta hybrid, however, is more widely distributed in southern Tennessee, the western tip of North Carolina, and northern areas of Mississippi, Alabama, and Georgia. Although hybridization occurred upon arrival of these two species in North America, S. invicta now occupies the remaining quarantined areas in North America (see http://aphis.usda.gOV) owing to its apparent displacement of S. richteri and the hybrid in this expanded range. Diffie et al. (1988, J. Entomol. Sd. 23: 187-91) initially reported the discovery of the hybrid ant in Alabama and Georgia and mapped its known distribution in Georgia, Alabama and Mississippi. Their survey included ants collected from 20 counties in Alabama and 11 counties in Georgia. The survey reported herein expands those

Effect of Red Imported Fire Ant (Hymenoptera: Formicidae) on Rhinocyllus conicus (Coleoptera: Curculionidae), a Biological Control Agent of Musk Thistle

Abstract The effect of the red imported fire ant, Solenopsis invicta Buren, on Rhinocyllus conicus Froelich in a musk thistle, Carduus nutans L., biological control program was evaluated in laboratory and field trials in pastures in middle Georgia in 1999 and 2000. In the laboratory, 30 thistle heads containing eggs and larvae were kept as controls and 30 heads were exposed to fire ant colonies. Foraging by fire ants for 72 h did not reduce the number of R. conicus eggs or larvae on musk thistle heads. Foraging by fire ant workers on musk thistle in pasture plots was nearly eliminated following treatment with Amdro bait (hydramethylnon). However, there were no noticeable differences in R. conicus egg, larva, or adult counts for thistle heads in treated and untreated plots. Results suggest R. conicus is largely unaffected by red imported fire ant activity on musk thistle.

Red Imported Fire Ant (Hymenoptera: Formicidae) Mortality Following Exposure to Sodium Hydrogen Carbonate (NaHCO3)

Red imported fire ant, Solenopsis invicta Buren, worker responses to sodium hydrogen carbonate (NaHCO3) placed on surfaces and in liquid food were evaluated in laboratory bioassays. The median leth...

MORTALITY OF ANT (HYMENOPTERA: FORMICIDAE) PEST SPECIES EXPOSED TO SODIUM HYDROGEN CARBONATE

Abstract Laboratory bioassays enabled us to determine the mortality of Argentine ant (Linepithema humile [Mayr]) workers, and red imported fire ant (Solenopsis invicta Buren) workers exposed to sodium hydrogen carbonate (NaHCO3, sodium bicarbonate). The median lethal concentration (LC50) of NaHCO3 for Argentine ants was 5.64 mg per cm2 after 5 d exposure and 3.96 mg per cm2 after 6 d. Cumulative mortality for Argentine ants exposed to 28 mg NaHCO3 per cm2 was 89.5% on day 6. Workers of both species were exposed to concentrations of 9.92, 17.70, or 152.00 mg NaHCO3 per cm2 in separate tests. Mortality of Argentine ants was significantly higher than that of fire ants following exposure to 9.92 mg NaHCO3 per cm2, while mortality for the two species did not differ following exposure to the two higher concentrations. Mortality of both species treated with the highest concentration exceeded 99% at 6 d. In tests with equivalent amounts of sodium in NaHCO3 and NaCl treatments, mortality for fire ants exposed to NaHCO3 was about 46% after 6 d. Mortality for fire ants exposed to NaCl was about 15% and was similar to that for untreated ants. Argentine ants were provided sugar water baits containing a range of NaHCO3 concentrations. Argentine ant mortality after 6 d exposure to 5% NaHCO3-sugar water treatment was about 50%. Mortality was not higher for workers exposed to higher concentrations of NaHCO3 in sugar water baits. Enzymatic dysfunction caused by unfavorable increases in internal pH is the most likely explanation for worker mortality following exposure to NaHCO3.

Argentine Worker Ant (Hymenoptera: Formicidae) Mortality Response to Sodium Salicylate and Sodium Cinnamate

Abstract The mortality response of Argentine worker ants, Linepithema humile (Mayr), following exposure to four phenolic compounds (sodium salicylate, sodium cinnamate, p-coumaric acid, caffeic acid) known to serve in plant defense mechanisms, boric acid, and sodium bicarbonate was assayed in laboratory testing. Argentine ant mortality after 3 days of exposure to sodium salicylate powder was significantly (F = 129.69; df = 3,2; P < 0.0001) higher than ant mortality in the untreated controls and in treatments with boric acid and sodium bicarbonate powders. Worker ant mortality after 3 days exposure to either sodium salicylate or cinnamic acid powder was significantly (F = 124.56, df =4,2, P < 0.0001) higher than mortality of worker ants in control, p-coumaric acid, and caffeic acid treatments. Assays with a range of concentrations (0,0.625, 1.25, 2.5, and 5.0%) of either sodium salicylate or sodium cinnamate dissolved in 10% sucrose solution showed significantly higher mortality with 5% sodium salicylate (F = 15.03; df = 4,2; P < 0.0001) and 5% sodium cinnamate (F = 30.14; df = 4,2; P < 0.0001) than the lower concentrations tested. In summary, salicylic acid and cinnamic acid, both in powder forms and liquid sucrose baits caused a higher Argentine worker ant mortality than either boric acid or sodium bicarbonate. Both appear to be promising candidates for further development as Argentine ant control products.

Bait Preferences of Ground-Dwelling Ants (Hymenoptera: Formicidae) in Central Georgia

Active searching, pitfall trapping, leaf litter sampling, and food baiting are commonly used together for capturing ground-dwelling workers of ant species (Ipser et al. 2004, Florida Entomol. 87: 253 260). Palm oil (Berghoff et al. 2003, Trop. Zool. 16: 153 163), ground meat (Apperson and Powell 1984, Florida Entomol. 67:383 393), grape jelly (Stein et al. 1990, Florida Entomol. 73: 117 123), and peanut butter (Oi et al. 1994, Florida Entomol. 77: 85 91) have been used as baits, but there is no standard. Brinkman et al. (2001, J. Entomol. Sci. 36: 461 463) found that tuna in oil attracted a greater diversity of ant species and numbers of workers for each species than 3 other foods tested. It is not known if combining different baits might attract more ant species and individuals than the individual baits alone. Thus, our objective was to compare the relative attractiveness of tuna in oil, sucrose, and a combination of the two to ground-dwelling ants. The 3 types of bait stations were prepared in the laboratory and transported to the study sites. Each tuna bait station was prepared by placing 2.5 g of tuna in oil on a 5-cm2 square of Parafilm®. The tuna and parafilm were then placed in a clear plastic 30-ml vial (Sarstedt AG & Co., Numbrecht, Germany) which served as the bait station. Each sucrose station was prepared by saturating a cotton ball (triple size, CVS Pharmacy Inc., Woonsocket Rl) in 20% (w/v) solution, placing the saturated cotton ball on a 5-cm2 square of parafilm, and then placing in a 30-ml vial that served as the station. The combination food bait station contained 1.25 g of tuna in oil and 1/2 of a sucrosesaturated cotton ball, together placed on a 5-cm2 square of parafilm in a 30-ml vial. Vials remained covered until they were placed at the study sites. The baits were compared at 2 sites in central Georgia. The first was in a wooded area, primarily Pinus taeda L., on the Gordon College campus (Lamar Co.). The other was at the Dauset Trails Nature Center (Butts Co.) with mixed pine and hardwood species. At each site, 8 locations were randomly selected so that the distance between

Red Imported Fire Ant (Hymenoptera: Formicidae) Control in Nursery Pots Treated with Beauveria bassiana and Bifenthrin

Beauveria bassiana (Balsamo) Vuillemin GHA strain was tested alone and in combination with different rates of bifenthrin for control of red imported fire ant, Solenopsis invicta Buren, in potted nursery medium. The fungus killed fire ant workers in the potting medium, but was not effective at eliminating infestations in all containers. Bifenthrin at a rate of 1.18 kg Talstar™ (nursery granular, 0.2% Al) per m3 soil alone performed better than B. bassiana alone; however, bifenthrin was also inconsistent in eliminating fire ants from all pots over the 4 yrs of the study. When B. bassiana was combined with reduced rates (1/4 and 1/2) of bifenthrin in 2001, infestations were eliminated from treated pots within 96 h each time workers were added to the pots for the 7-wk test period. The number of infested bifenthrin + B. bassiana-treated pots was significantly lower than the number of infested untreated pots on all 19 sampling dates in 2001. Use of bifenthrin + B. bassiana was as effective or more effective tha...

Genetic Variation in Aphthona nigriscutis Foudras (Coleoptera: Chrysomelidae) Populations Introduced into the United States to Biologically Control Leafy Spurge

Cellulose acetate electrophoresis was used to examine the levels and distribution of genetic diversity in Aphthona nigriscutis Foudras populations 5 to 9 yrs following their introduction to sites i...