2000), and PCR-based vacuum extraction ( Bextine et al. fastidiosa in natural and experimental environments including transmission ( Purcell and Finlay 1980), insect head culture ( Almeida and Purcell 2003), plant tissue culture ( Hill and Purcell 1995), chloroform/phenol extraction ( Frohme et al. Many methods have been developed to detect X. fastidiosa ( Almeida and Purcell 2006), but there is little data on naturally occurring infectivity ( Daane et al. Greenhouse studies suggest that between 10% and 20% of H. Additionally, the grape and almond strains were unable to cause disease symptoms in oleander. fastidiosa are host specific and in transmission studies, the strain that causes disease symptoms in oleander will not cause disease symptoms in grape or almond. 1976), and oleander leaf scorch ( Purcell 1999). 1993 Pooler and Hartung 1995), almond leaf scorch ( Mircetich et al. fastidiosa, resulting in a multitude of plant diseases such as citrus variegated chlorosis ( Chang et al. Many economically important plants include-ing citrus, almond and oleander are affected by separate strains of X. 1997), grapevines showing characteristic symptoms must be uprooted and replanted, usually resulting in a two or three year loss of individual plant productivity. As there is currently no cure for Pierce’s disease ( Pooler et al. fastidiosa can cause systemic failure of a grapevine within one to five years of initial infection, and previous studies have shown that as few as 100 cells can initiate an infection ( Hill and Purcell 1995). In the grapevine ( Vitis sp.), Pierce’s disease symptoms include marginal leaf scorch, chlorosis, necrosis, stunted growth, leaf loss, and dieback, all of which result from occlusion of the xylem tissue by polymeric matrix enclosed bacterial aggregates attached to the inner xylem wall ( Hopkins 1989). fastidiosa infection in grapevines may result in Pierce’s disease, which has caused major losses in both wine and table grape production in the USA ( Davis et al. Indirectly, plant damage is done by the transmission of the xylem-limited bacterium, Xylella fastidiosa Wells (Xanthomonadales: Xanthomonadaceae). vitripennis feeding can impact plant health directly by depriving the plant of nutrients and damaging the xylem sufficiently to preclude vascular flow. They have been reported to feed on host plants from at least 35 families, including both woody and herbaceous types ( Hoddle et al. vitripennis have the ability to ingest in excess of 100 times their weight in xylem fluid in a single day ( Purcell 1999). vitripennis can spread quickly once established and have recently been found in French Polynesia, Tahiti, and Hawaii ( Hoddle et al. With the ability to travel long distances, H. vitripennis have established populations in southern California and have negatively affected the wine grape industry (Founier et al. Without naturally occurring forms of biological control, H. The glassy-winged sharpshooter, Homalodisca vitripeninis Germar (Hemiptera: Cicadellidae), is an insect pest that is present in most of the southern region of the USA and is an endemic pest throughout most regions of Texas ( Young 1958 Turner and Pollard 1959). fastidiosa homologous to known Pierce's disease strains, signifying them as a risk factor for new X. Furthermore, all three insects were determined, by DNA sequencing, to be carrying a strain of X. vitripennis collected from vineyards with no history of Pierce’s disease tested negative for the presence of the pathogen, three individual insects tested positive. vitripennis from vineyards known to have Pierce’s disease routinely tested positive for the presence of X. fastidiosa and have the potential to transmit this pathogen. vitripennis within each population that harbor X. The foregut contents were vacuum extracted and analyzed using RT-PCR to determine the percentage of H. vitripennis collected during 20 over the months of May, June, and July from eight vineyards in different regions of Texas were recovered from yellow sticky traps and tested for the presence of X. To that end, the USDA-APHIS has developed a program to sample vineyards across Texas to monitor populations of H. fastidiosa into Pierce’s-disease-free areas is critical for developing a management program for Pierce’s disease. vitripennis populations capable of transmitting X. vitripennis is the main vector of Xylella fastidiosa Wells (Xanthomonadales: Xantho-monadaceae), the bacterium that causes Pierce’s disease of grapevine and can travel long distances putting much of Texas grape production at risk. The glassy-winged sharpshooter, Homalodisca vitripeninis Germar (Hemiptera: Cicadellidae), is a xylophagous insect that is an endemic pest of several economically important plants in Texas.
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