Investigation of potential plant reservoir hosts of Xylella fastidiosa in Oklahoma

Xylella fastidiosa Wells et al. is the causative agent of many plant diseases including those of peach and plum, leaf scorch of oleander, almond, elm, oak, and sycamore, and Pierce’s disease of grapes. With recent reports of Pierce’s disease in five Oklahoma vineyards, it is important to understand the epidemiology of the bacterium in this state. We hypothesized that landscape vegetation including both weedy and ornamental plants may serve as reservoir hosts of X. fastidiosa in Oklahoma. Mechanical inoculation studies were used to determine if selected plants are able to support X. fastidiosa populations, and if so, whether they express disease symptoms. Plants selected for this study are preferred food sources of xylem fluid-feeding insect vectors and are commonly found in Oklahoma landscapes. Selected plants are sunflower (Helianthus annuus L.), morning glory (Ipomoea spp.), thistle (Cirsium spp.), ragweed (Ambrosia L.), and bermudagrass (Cynodon dactylon (L.) Pers.). Plants were mechanically inoculated with X. fastidiosa cells suspended in phosphate buffered saline (PBS). Each treatment included ten plants replicated three times. The control group was inoculated with PBS only. Plants were kept under controlled conditions for three months and monitored for symptom development. We present results of the inoculation study and discuss implications for managing insect vectors that transmit X. fastidiosa to economically important crops.