Bermudagrass stem maggot: An exotic pest in the southeast USA

Since first discovered in southern Georgia in July 2010, the bermudagrass stem maggot (BSM; Atherigona reversura Villeneuve) has infested and damaged bermudagrass (Cynodon dactylon) hayfields throughout the southeastern United States but there is a paucity of information about the biology and management of this new invasive pest. Our objectives are to compare the severity of damage among selected cultivars, determine if there are phenotypic differences in the cultivars that are preferred by the BSM, and assess the fecundity of the BSM on the different varieties.  Eight Cynodon cultivars were used in this study. Flies collected from infested bermudagrass fields were introduced six times throughout the 4-wk growing period to the cultivars, which were grown in the greenhouse and contained in acetate and mesh enclosures. Every four weeks the forage was harvested and morphological characteristics analyzed. Preliminary results show that some varieties have more and a higher percentage of shoots damaged by the BSM than others. There was a trend for the more heavily damaged varieties to have finer stems. In addition, damaged plants tended to have darker leaves and a thicker stem, possibly due to a reallocation of nutrients. In this study, fly damage did not result in a significant yield reduction yet a difference in BSM fecundity among cultivars was found. Additional research is underway to better understand the lifecycle of this species; confirm and quantify the degree of preference A. reversura has for bermudagrass cultivars; and quantify the severity of damage in yield, quality, and aesthetics.