Distribution and foraging by the leaf -cutting ant, Atta cephalotes L., in coffee plantations with different types of management and landscape contexts, and alternatives to insecticides for its control.

摘要

Atta cephalotes L., the predominant leaf-cutting ant species found in coffee farms in the Turrialba region of Costa Rica, is considered a pest of the crop because it removes coffee foliage. I applied agroecosystem and landscape level perspectives to study A. cephalotes foraging, colony distribution and dynamics in coffee agroecosystems in the Turrialba region. I also conducted field assays to assess effects of control methods on colonies of different sizes and to examine the efficacy of alternatives to insecticides.;Colony density (number of colonies/ha) and foraging of A. cephalotes were studied in different coffee agroecosystems, ranging from monoculture to highly diversified systems, and with either conventional or organic inputs. A. cephalotes colony density was higher in monocultures compared to more diversified coffee systems. The percentage of shade within the farm was directly related to A. cephalotes colony density. The proportion of coffee plant tissue being collected by A. cephalotes was highest in monocultures and lowest in farms with complex shade (more than three shade tree species present).;Number of colonies and total surface area of colonies were greater near the edges of coffee farms than closer to the interior (>30 m from edge). This effect was significantly stronger for edges adjacent to riparian forest strips than other edge types. There was only limited evidence of the influence of landscape features at greater distances from farms (up to 2000 m) on within-farm colony densities.;Sulfluramid and sodium octoborate caused the greatest mortality among 9 treatments tested in bait formulations on A. cephalotes colony activity and mortality. One of the alternative baits tested (active ingredient, propagules of Paecilomyces sp. 0484) caused significant reduction in colony activity (worker movements into and out of nest openings), but failed to cause significant colony mortality. Effects of treatments on colony activity were stronger on large (>30 m2 of nest surface area) than on medium (1.1-30 m2) and small colonies 0.03-1 m2.;Coffee farmers would benefit from reduced attack by A. cephalotes by increasing the amount of shade, planting shade species palatable to A. cephalotes but economically unimportant or capable of withstanding ant attacks.