Identification of visual and olfactory stimuli for cornsilk flies (Euxesta sp) management

Abstract

Background: Maize (Zea mays L.) is the most widely cultivated cereal in the world. The introduction of the Bt gene and the development of sweet corn varieties with softer pericarp has led to the emergence of new pests in the genus Euxesta (Diptera: Ulidiidae), previously considered as secondary invaders. In Argentina, Euxesta eluta and Euxesta mazorca predominate. Some control measures are being implemented; however, no biorational control strategies have been developed to date. With aims at developing effective monitoring traps, this study investigated visual and olfactory stimuli that attract Euxesta sp. Results: Three experiments were conducted in the laboratory and the field: (i) on visual stimuli; color, tonality, shape, size, and contrast. Mature flies were attracted to blue, rectangular, large traps. Contrast did not have an effect on capture. (ii) Olfactory stimuli: intact ears and ears with lepidopteran damage were compared in a two-way stationary olfactometer. There was a higher offspring yield from damaged than intact ears. (iii) Field response to baits was evaluated: Plustrap, torula yeast, hydrolyzed protein with borax, and spinosad. Traps with hydrolyzed protein with borax captured the highest number, followed by traps with torula yeast. For these two baits, the number of females captured was higher than males. E. eluta was more abundant than E. mazorca. Conclusion: This study provides key information for the development of monitoring tools for Euxesta sp., highlighting the importance of visual and olfactory stimuli in capture. Implementing traps based on these findings can be used for management in maize.