Seasonal Timing, Abundance, and Predatory Status of Arthropods Associated with Corn Infested by Picture-Winged Flies (Diptera: Ulidiidae) in South Florida

Since the 1960s, the USA has led all other countries in the production of sweet corn (Zeamays L.), and Florida has often led the nation, such as from 2004 to 2009. Picture-winged flies, or corn silk flies, including Euxesta stigmatias Loew, E. eluta Loew, E. annonae F., and Chaetopsis massyla Walker (Diptera: Ulidiidae), are serious pests of field and sweet corn in southern Florida. Control has focused on the use of chemical insecticides, but efforts have begun to explore other control methods, such as using predatory arthropods. We studied the timing, abundance, identification, and predatory status of ulidiids and other arthropod species associated with corn ears growing in the field in the spring, summer, and fall of 2010. Predators of ulidiids included Orius insidiosus Say (Hemiptera: Anthocoridae), Anotylus insignitus (Gravenhorst) (Coleoptera: Staphylinidae), Chrysoperla carnea Smith (Neuroptera: Chrysopidae), Zelus longipes (L.) (Hemiptera: Reduviidae), and potentially other arthropod species. Larvae of A. insignitus, C. carnea, and nymphs and adults of O. insidiosus consumed eggs and larvae of ulidiids in laboratory no-choice tests. Other than ulidiid eggs and/or larvae, O. insidiosus was the most abundant arthropod species in the silking (R1) stage of corn in all 3 seasons. Sap beetle larvae or adults (Coleoptera: Nitidulidae) were the most abundant arthropod groups in the spring blister stage (R2) and in milk stages (R3) of the spring and fall. The most abundant groups in the summer R2 and R3 stages included A. insignitus larvae and sap beetle larvae and adults, and in the summer R2, also O. insidiosus. The most abundant groups in the fall R2 were O. insidiosus, sap beetle adults, Thrips sp. (Thysanoptera: Thripidae), and mites. Chrysoperla carnea was found only in the summer, and Z. longipes only in the fall. In all 3 seasons, ulidiid eggs were more abundant than larvae in the R1 stage, but larvae usually outnumbered eggs in the R2 and R3 stages. Each of the groups, O. insidiosus and eggs and larvae of ulidiids, were most abundant in the summer followed by the fall and least abundant in the spring. These findings may help in determining spatial distributions and functional responses of these predators to further evaluate their potential to control ulidiid flies.