Distribution of Arthropod Predators and their Responses to Euxesta spp. (Diptera: Ulidiidae) in the Laboratory and in Corn Fields in South Florida

Injury caused by picture-winged flies or corn silk flies (Diptera: Ulidiidae) is a major limiting factor of corn (Zea mays L.: Poales: Poaceae) yields in Florida. Growers have relied heavily on chemical insecticides for control of these pests. However, we are exploring other methods, such as the use of biological control by predatory arthropods, which may be factors in an integrated pest management (IPM) program. Thus, information on the distribution of the flies and their predators and responses of the predators to the flies is potentially useful. Taylor's Power Law, Iwao's Patchiness Regression, and the Index of Dispersion were used to study distribution patterns of arthropods found on sweet corn ears in 2010. Arthropod groups included eggs and larvae of Euxesta stigmatias (Loew), E. eluta (Loew), E. annonae F. (Diptera: Ulidiidae), nymphs and adults of Orius insidiosus (Say) (Hemiptera: Anthocoridae), and larvae of Anotylus insignitus (Gravenhorst) (Coleoptera: Staphylinidae). In each season in the R1, R2, and/or R3 corn stages, ulidiid eggs and larvae generally had aggregated distributions in corn ears (b, β, & ID > 1; P < 0.05). Orius insidiosus had aggregated distributions on most sampling dates except for random or regular distributions (b, β, & ID ≤ 1) in the R3 stages of the spring and fall. The distribution of A. insignitus larvae was measured only in the summer R3 and was aggregated. In the laboratory, O. insidiosus had a Type III functional response to eggs of E. stigmatias, E. eluta, and E. annonae, and the combination of these species with similar handling times (0.43–0.45 h) and attack constants (0.03–0.05h⁻¹) for the different prey species. These results for O. insidiosus may be compared to those of Zelus longipes (L.) (Hemiptera: Reduviidae) and other predators, which may help elucidate the effectiveness of these predators in controlling ulidiid flies.