Evaluation of three sampling methods for monitoring adult corn silk flies (Diptera: Ulidiidae) in sweet corn

In Florida, Euxesta stigmatias, Euxesta eluta, and Chaetopsis massyla are three picture-winged fly (Diptera: Ulidiidae) species referred to as corn silk flies. These silk flies are important pests of sweet corn, with maggots attacking the ears and making the crop unmarketable. Monitoring adult populations of silk flies is a key component of their management with insecticides. During 2019, two field experiments were conducted to compare the efficiency of adult monitoring with three sampling methods for corn silk flies. These sampling methods included the direct visual observation of adults on sweet corn plants, the use of multilure traps baited with ammonium acetate and 1,4-dimethoxybenzene, and the use of yellow sticky cards (7.6 by 12.7 cm). Corn silk fly adult observations with the three sampling methods were correlated. In addition, multilure traps captured more E. stigmatias adults than sticky cards whereas sticky cards captured more C. massyla adults than multilure traps. Results suggest that the three sampling methods assist in detecting corn silk fly adult population level fluctuations. Importantly, multilure traps perform best for E. stigmatias, which is the most challenging of the three silk fly species to manage with insecticides. Nevertheless, multilure traps have not been widely adopted because crop consultants have continued using direct plant observations for monitoring silk fly populations. Promoting the use of traps will assist stakeholders in making better pest management decisions. Future work to understand the relationship between adult corn silk fly trap captures and landscape composition are also discussed.