Field Edge and Field-to-Field Ecotone-Type Influences on Two Cotton Herbivores: Cotton Fleahopper, Pseudatomoscelis seriatus (Hemiptera: Miridae), and Verde Plant Bug, Creontiades signatus

In the United States, the average field size has roughly doubled from the 1980s to the mid-2000s, while average cropland has stayed the same. This will likely influence how semi-natural habitats and edges affect local patterns and processes such as natural pest control or pest densities. We hypothesized that densities of two cotton pests, cotton fleahopper (Pseudatomoscelis seriatus) and verde plant bug (Creontiades signatus) (Hemiptera: Miridae), and corresponding cotton injury in a cotton agroecosystem were affected by field edge, ecotone type (described by the neighboring habitat), and the influence of ecotone type on edge effects. Studies over 2 yr using transect and random point sampling indicated that densities of both insects declined significantly and in a linear fashion from the cotton field boundary (0 m) to field interior (200–300 m from field edge). The decline was influenced by ecotone type for cotton fleahopper. Pest densities in cotton at the interface with semi-natural habitat were higher but declined at a greater rate into the cotton field interior compared to densities seen at the interfaces with sorghum or another cotton field. These effects were also observed for verde plant bug and the cotton boll injury it causes. Regardless of the pest densities near the field edge and the rate of decline into the field interior, densities beyond 100 m into the field were up to 70% less than field edges for both insect species and for boll injury. Potential for land managers to improve sampling efficiency when scouting is apparent. For example, pest species may be at economic threshold in certain parts of the field but not others, leading to different management decisions in larger fields. Therefore, for cotton fleahopper and verde plant bug, edges should be the focus of initial pest detection and sampling, and interior field sampling may only be required when edges are above the economic threshold.