Resistance in Maize to Euxesta stigmatias Loew (Diptera: Otitidae)2

Abstract

The corn silk fly, Euxesta stigmatias Loew (Diptera: Otitidae), and related otitid species can cause severe crop losses to sweet corn, Zea mays L., grown in tropical and subtropical regions. In Florida, the fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), and E. stigmatias are two debilitating insect pests on the sweet corn ear that are considered the most costly and difficult to control. Our purpose was to search for resistance to the corn silk fly in a diverse set of maize germplasm that included sweet, floury, field and popcorn, and to determine if any empirical relationship existed between E. stigmatias damage and S. frugiperda infestation in corn ears. The overall means across two sites, 3 yrs and 16 genotypes was 1.77 for corn silk fly damage, rated on a 0 to 4 prototype scale, and 30.1% for fall armyworm infestation. Clear differences existed between the sweet and popcorn types when compared to the field and floury types. The field and floury corns sustained significantly less damage by the corn silk fly than the sweet and popcorn types (0.91 vs 3.33). Five of these genotypes, CEW-R58, DDSB, GT-RI4, Mp704 and ‘Zapalote Chico 2451’, had both lower corn silk fly damage ratings and lower levels of fall armyworm infestation. Across this broad germplasm base no statistical relationship was identified between corn silk fly damage and fall armyworm infestation, suggesting that each insect species responds independently to different maize genotypes. Husk extension was partly related to reduced S. frugiperda infestation, and tip tightness was partly related to reduced E. stigmatias damage. These results indicate that field corn could possibly serve as source of resistance to the corn silk fly for the improvement of sweet corn.