Color, pattern and background contrast affect attraction of Euxesta eluta and Chaetopsis massyla (Diptera:Ulidiidae)

Authors: Allan, Sandra - Sandy

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2023
Publication Date: 1/10/2024
Citation: Allan, S.A. 2024. Color, pattern and background contrast affect attraction of Euxesta eluta and Chaetopsis massyla (Diptera:Ulidiidae). Environmental Entomology. https://doi.org/10.1093/ee/nvad120.
DOI: https://doi.org/10.1093/ee/nvad120

Interpretive Summary: The corn silk flies, Euxesta eluta and Chaetopsis massyla, are important pests of fresh market sweet corn in Florida with significant losses yearly due to larval feeding on the ears. Control is primarily through repeated pesticide applications when fly populations threaten developing ears. Pest surveillance, used to guide control decisions, is primarily through time-consuming visual inspection, however there no standardized surveillance methods for these insects. To better understand aspects of visual attraction for these flies as a foundation for trap development, a scientists at USDA/ARS in Gainesville, FL evaluated various attributes that influenced visual responses of the flies. Using colored sticky traps, the optimal colors for attracting flies were determined with differences in preference between the species. The presence of black or white backgrounds also influenced fly response as did trap shape and complexity of pattern on traps. These attributes provide valuable insight into development of an effective surveillance technology for these flies.

Technical Abstract: Euxesta eluta Loew and Chaetopsis massyla Walker (Diptera: Ulidiidae) are primary pests of sweet corn in Florida. Attraction of adult flies to various visual stimuli were evaluated in the laboratory to provide insight in potential development of enhanced trapping strategies. In assays evaluating different colored sticky traps, more E. eluta were collected on light blue, mid blue, lime green and orange yellow traps, whereas attraction of C. massyla was greater to lime green and fluorescent green traps. In a comparison of different yellow 3-dimensional shapes, more E. eluta were collected on yellow cylinders than on spheres or cubes, however more C. massyla were collected on cylinders than cubes or spheres. When colored traps were placed against a white background, more E. eluta were collected on lime green traps compared to yellow, blue and orange traps, however when placed against a black background, attraction to the lime green trap was reduced. Attraction of C. massyla, was strongest to yellow, then lime green and orange traps followed by blue against the white background but with a black background, differences between traps collections were reduced. Addition of UV reflectance to yellow increased attraction of E. eluta but C. massyla was more attracted to yellows without UV reflection or fluorescence. Addition of black patterns on yellow traps affected attraction with E. eluta more attracted to wide stripes, a large square or many small squares, whereas C. massyla was more strongly attracted to stripes. Utilization of these visual attributes could be useful in improving surveillance for these species.