Corn-infesting picture-winged flies: Distribution in field by time and space

Four species of picture-winged flies, Euxesta annonae (F.), E. eluta Loew, E. stigmatias Loew, and Chaetopsis massyla (Walker) damage corn ears in Florida. Studies were conducted to determine the distribution of these flies in commercial and experimental sweet corn fields in southern Florida during Fall 2007 through Summer 2010. Adults were sampled using yellow sticky cards placed in fields during the reproductive stage. Cards were examined for adult flies every 1 to 5 days depending on the REI of treated fields. Corn ears were sampled for immature stages of flies at harvest. Distributions were studied in relation to insecticide applications and plant age. Flies were present throughout fields and throughout the periods between silking and harvesting. The flies distributed themselves in an aggregated manner in commercial fields but in a uniform manner in small scale fields. It was also found that the flies were present the next day after spraying the insecticide. Species distribution of adults will be presented in relation to larvae-infested ears. Information on spatial and temporal distribution is critical for the development of sampling plans and economic thresholds for these flies.