Author
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Wiltz, Beverly |
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Submitted to: Ph D Dissertation
Publication Type: Other Publication Acceptance Date: 5/1/1996 Publication Date: N/A Citation: Wiltz, B.A. Fire Ant Re-establishment in Grass Habitats after Treatment with Insecticides. Louisiana State University. 77 pp. 1996. (Masters Thesis). Interpretive Summary: The red imported fire ant, Solenopsis invicta Buren, is an important pest throughout most of the southeastern United States, creating hazards to humans, livestock, and wildlife. Mound densities are highly variable due to a combination of factors, including the success of founding queens, ground cover, history of chemical control, competition from other ant species, and frequency of disturbance. Control tactics include the use of contact insecticides, either as a barrier, broadcast, or mound treatments, and the use of baits, which are more target specific and control ants using less toxicant. While individual mound treatments provide rapid control of colonies, ants frequently relocate following treatment. The most effective control strategies often combine multiple treatment techniques. The objectives of this study were to track the movement and re-establishment of the red imported fire ant into areas where it has been eliminated with insecticides and to develop a framework for red imported fire ant treatment thresholds. Following elimination of fire ants from plots, the diameter and coordinates of each mound in the treated circles and the 0.12 ha ring surrounding each were recorded at intervals of approximately two weeks from March – October 1994. The study was repeated using different plots at the same site in 1995. Although mound densities were lower in 1995 than 1994, there was little difference between the two years in the percentage re-establishment over time. Through regression analyses of percent re-establishment over time, treatment interval guidelines were developed for given pretreatment fire ant mound densities and treatment thresholds. The frequency of fire ant mound sizes in treated and untreated areas was significantly different in 1994 but not in 1995. The percentage change in the diameter of individual mounds through time was not significantly different between treated and untreated areas in either year. Newly located mounds contained workers of varying sizes which indicated that they were formed by budding from colonies in the surrounding area. Technical Abstract: The objectives of this study were to track the movement and re-establishment of the red imported fire ant, Solenopsis invicta Buren, into areas where it has been eliminated with insecticides and to develop a framework for red imported fire ant treatment thresholds. The study was conducted at Burden Research Plantation in Baton Rouge, Louisiana, a site containing polygyne fire ant populations. Five circular plots were treated in March of 1994 and an additional in March of 1995 to eliminate all of the fire ant colonies within the inner 0.09 ha of the plots. The diameter and coordinates of each mound in the treated circles and the 0.12 ha ring surrounding each were recorded at intervals of approximately two weeks though October 1994 and September 1995. For each plot, the number of mounds per area (ha) was calculated along with the ratio of treated mound density to untreated mound density. Although mound densities were lower in 1995 than 1994, there was little difference between the two years in the percentage re-establishment over time. Through regression analyses of percent re-establishment over time, treatment interval guidelines were developed for given pretreatment fire ant mound densities and treatment thresholds. The frequency of fire ant mound sizes was compared for the treated and untreated areas and found to be significantly different in 1994 but not in 1995. The percentage change in the diameter of individual mounds through time was not significantly different between treated and untreated areas in 1994 or 1995. Newly located mounds contained workers of varying sizes which indicated that they were formed by budding from colonies in the surrounding area. |
