Date of Award

5-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Entomology

Advisor

Eric P. Benson

Committee Member

Patricia A. Zungoli

Committee Member

Patrick Gerard

Committee Member

Simon W. Scott

Abstract

Linepithema humile (Mayr), the Argentine ant, is an invasive ant species and a significant pest in natural and managed habitats of the southeastern United States. In the natural sites of Lake Greenwood State Park (LGSP) in the Piedmont region of South Carolina, L. humile has invaded. Although park personnel treat problem areas with liquid insecticides, control of L. humile through the park areas is minimal. The primary objectives of this study were to determine the optimal foraging distance of L. humile, evaluate over-wintering nest temperatures and foraging activity of L. humile, and evaluate liquid bait placement to control L. humile. A Double Antibody-Sandwich Enzyme-Linked Immunosorbent Assay (DAS-ELISA) procedure was used to detect individual ants that had consumed rabbit Immunoglobin (IgG) protein (Sigma Chemical Co., St. Louis, MO) for marking and tracking. In this study, the optimal concentration of IgG in an individual ant necessary for detection was determined to be 0.01mg/ml. In both lab and field conditions, there was a significant difference in the detection of IgG in ants fed the protein marker mixed with sugar water compared to ants only fed sugar water. Additional field studies found that an individual ant could retain detectable levels of the protein marker for 3 d and that ants feeding IgG containing bait could be significantly detected up to15 m from the original bait source. In a field at LGSP, Greenwood, SC, bait stations containing 300ml of 30% sugar-water with 0.01 mg/ml of IgG protein were placed in a grid pattern with nine stations placed at 10 m apart and were compared to nine stations in a grid pattern place at 20 m apart. This study was replicated three times. When the distance between the two bait station placements was compared, the amount of IgG detected in L. humile was significantly higher in ants foraging at stations 10 m apart compared to ants foraging at stations at 20 m apart. However, IgG could be detected in ants foraging to stations 20 m. To be cost effective for the amount of bait needed, stations needed and time for labor, 20 m was selected for a later field trial to control L. humile. The over-wintering habitat study showed that mean L. humile nest temperatures were less variable than mean ambient temperatures. From January to March, 2012, the range from lowest to highest temperature was 12.4°C in the nests and 21.7°C in the ambient environment. During this period, the lowest mean temperature recorded in the ambient environment was 8.27°C and 10.01°C in the nests. The highest mean temperature was 30.0°C in the ambient environment and 22.5°C in the nests. Even though ambient and nest temperature fluctuated, the mean foraging activity of L. humile increased from 12 February to 29 February. After 16 March, both the mean ambient temperatures and the nest temperatures continued to be over 15°C. At this temperature, L. humile began to actively forage. This result suggested the optimal bait placement date for control of L. humile was after 16 March due to temperature (ambient and nest) and ant foraging activity. A bait study was conducted in natural areas of LGSP to determine early season control of L. humile using the 20 m bait placement discovered in the earlier study. When temperatures were continuously above 15°C in 2012, three treatment areas were established. These areas included a natural control area with no bait placement, a bait control area with stations containing 200 ml of 25% sugar water, and a bait treatment area with stations filled with 180 ml of 25% sugar water mixed with 20 ml Maxforce Quantum Ant Bait (0.03% imidacloprid). In each area, 10 trees with active L. humile trails were selected to assess foraging activity. The ant trail with the greatest number of individuals on each tree was counted weekly. Liquid bait stations were placed in three rows at 20 m apart. Bait was replaced weekly for three months. The mean number of L. humile was recorded from spring to fall in 2012 and from spring to early summer in 2013. No bait was used after June 2012. Liquid ant bait decreased the L. humile population in the treatment area after one season of baiting as compared with the control areas. It was conclude that early season liquid baiting (mid-March), with a specific placement distance (20 m), was an effective method for controlling L. humile in a natural park habitat in South Carolina.

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