PLANT-GWSS INTERACTIONS: PHYSIOLOGICAL AND BIOCHEMICAL MECHANISMS INVOLVED IN HOST PLANT SELECTION WITH PARTICULAR REFERENCE TO LEMON AND ORANGE TREES

• Author(s): Castle, Steven; Toscano, Jian;
• Abstract: The glassy-winged sharpshooter (GWSS) Homalodisca coagulata is an exotic insect in California and is an important vector of Xylella fastidiosa that causes Pierces disease (PD) in grapes. Citrus is a favored host of GWSS throughout the year, and it has been well documented from studies of the Temecula PD epidemic that the proximity of citrus groves to vineyards has influenced the incidence and severity of PD in grapes. It is imperative that effective control strategies be implemented to curb the spread of the vector-vital to this would be establishing the host plant range of the GWSS and determining the physiological and biochemical mechanisms for host selection. One of the key factors contributing to the successful establishment of the GWSS in California has been its ability to utilize more breeding habitats and plant hosts than native PD vectors. Although a comprehensive list of suitable hosts has been identified, comprising 75 plant species in 35 families, little is known about the physiological and biochemical mechanisms involved in host selection of GWSS in California. Elucidation of the physiological and biochemical mechanisms may be usable for developing host plant resistance as a sustainable component of integrated pest management program. Dietary nitrogen and carbohydrates are important nutritional indices impacting survival, growth and reproduction of phytophagous insects. These nutrients are particularly limited for xylophagous insects, such as GWSS, because xylem fluid consists of over 95% water and is the most dilute food source for herbivores. There are two ways in which the GWSS could compensate for the poor nutrient quality of the xylem fluid. Firstly, they could feed for extended periods of time. This is, in fact, known to be the case, as those of us who have witnessed the sharpshooter rain at first hand will attest. Indeed, it has been estimated that GWSS can process up to 10 ml of xylem fluid per day. Secondly, efficient assimilation of available nutrients during prolonged feeding periods would enhance the nutritional value of xylem. Different host plants may contain different levels of dietary nitrogen and carbohydrate during the year and the differences could play a role in GWSS host selection.
• Publication Date: Dec 2002
• Journal: 2002 Pierce's Disease Research Symposium