The Occurrence of Xylella fastidiosa and Its Sharpshooter Vectors in Selected Alabama Orchards and Vineyards

Abstract

Although the bacterium Xylella fastidiosa (Xf) has been confirmed to cause economic losses to numerous fruit crop species in the southeastern U.S. since 1933, no science-based information is available on the occurrence of infection in economic fruit crops grown in Alabama, as well as the presence of effective Xf vectors in the state. Our investigation aimed to determine the spread of Xf infection in selected major fruit crops, and to identify the sharpshooter (Hemiptera: Cicadellidae) fauna in selected orchards and vineyards grown at three distinct chilling zones in Alabama. Our study confirmed the occurrence of Xf in all six fruit crops grown throughout the three chilling zones in Alabama, and the highest disease pressure was found in the Gulf Coast area. The following sharpshooter species were recorded in Alabama: Homalodisca vitripennis (Germar), H. insolita (Walker), Oncometopia orbona (Fabricius), Paraulacizes irrorata (Fabricius), Graphocephala coccinea (Forster), G. versuta (Say), and Draeculacephala spp. H. vitripennis was the most abundant species in the Gulf Coast area, whereas G. versuta was the dominant species in Central and North Alabama. The preliminary data obtained from our study could be further utilized to develop a degree-day model to predict sharpshooter emergence in various Alabama locations and aid fruit growers in their management practices.