Factors affecting detection of red imported fire ant, Solemopsis invicta Buren, mounds with aerial photography

Abstract

Studies conducted in the Texas coastal plains during the period July 1971 through May 1974 demonstrated that mounds of the red imported dire ant, Solenopsis invictaBuren, can be detected on natural color (NC), color infrared (CIR) and black and white infrared (BWIR) with aerial photographs of ant-infested land. Analysis of aerial photographs taken with a modified Fairchild K-37 camera and a Hasselblad camera indicated that up to 90% of the total fire ant mounds resent in research plots could be visually detected on photographs having scales of 1:2500. Photographic scales between 1:2000 and 1:3000 appear to be the ones best suited for obtaining a high level of mound detection accuracy while maintaining the maximum amount of land surface area per frame possible. CIR and BWIR film types appear to be superior to NC film enabling a person to visually detect fire ant mounds on resulting photographs. Also, visual mound detection capabilities of the interpreter on photographs seemed to be least affected by seasonal changes in the environment when CIR film was used. The period from late winter to early spring proved to be the optimum time for detecting red fire ant mounds in typical pastureland sites. The optimum period for detecting fire ant mounds on CIR photographs of rice management areas of the Texas coastal plains is just prior to the first killing freeze during the winter and in early spring when lush vegetation begins to grow on the mound surfaces. In general mounds greater than 3 in in height and 13 in in diameter, and having 0-20 or over 60% vegetative mound cover were detected more readily by the photointerpreter than mounds in other categories. The appearances of ant mounds varied in accordance with the film type used and the season of the year when photographs were taken..