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United States Department of Agriculture

Agricultural Research Service

Title: Epidemiology of Pierce's Disease in the Central San Joaquin Valley of California: Factors Affecting Pathogen Distribution and Movement

Authors
item Groves, Russell
item Chen, Jianchi

Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: December 1, 2004
Publication Date: December 7, 2004
Citation: Groves, R.L., Chen, J. 2004. Epidemiology of Pierce's Disease in the Central San Joaquin Valley of California: Factors affecting pathogen distribution and movement. Proceedings of the 2004 Pierce's Disease Research Symposium. p. 103-105.

Interpretive Summary: This research addresses the seasonal abundance, dispersal, and overwintering biology of the glassy-winged sharpshooter (GWSS), a primary vector of the bacterium, Xylella fastidiosa (Xf), the pathogen responsible for Pierce's disease in grapevines and almond leaf scorch disease. The goal of this research was to identify where the vector(s) acquire the pathogen, to determine when vectors move into vineyards and transmit the pathogen to grapes, and to characterize the populations of pathogen carried by GWSS. Based on results in our study through the winter of 2003-04, we conclude that host plant species can significantly influence GWSS population biology. GWSS adult, nymph, and egg mass densities varied among sweet cherry, navel, lemon, olive, avocado, peach, plum, pomegranate, pistachio, and grape. Adult GWSS were found in a wide range of crops with the largest populations observed in citrus (lemon and navel) and pomegranate, similar to our findings in 2003. Adult GWSS were also regularly observed feeding upon annual weeds surrounding orchard crops. Juvenile insects were not always present on the same perennial tree crops. Overwintering adult GWSS were found on citrus, pomegranate, avocado, plum, peach, and non-crop annual weed species. Adult GWSS dispersed into citrus and pomegranate much farther than the remaining crop species examined. The presence of the bacteria in insects collected from different crops and weeds is underway using a molecular tests.

Technical Abstract: The primary objective of this research was to characterize the seasonal abundance, dispersal, and overwintering biology of the glassy-winged sharpshooter (GWSS), a primary vector of Xylella fastidiosa (Xf). Moreover, to identify where the vector(s) acquire the pathogen, to determine when vectors move into vineyards and transmit the pathogen to grapes, and to genetically characterize the populations of Xf isolated from GWSS collected in different perennial cultivated and non-cultivated plant species. Based on results of seasonal plant utilization by GWSS in our study through the winter of 2003-04 and into the subsequent growing season, we conclude that host plant species can significantly influence GWSS population biology. GWSS adult, nymph, and egg mass densities varied among perennial, cultivated crop plant species and non-cultivated weed species examined in this study. Perennial crop species examined included sweet cherry, navel, lemon, olive, avocado, peach, plum, pomegranate, pistachio, and grape. Adult GWSS dispersed into and fed upon a wide range of these crop species with the largest dispersing populations observed in citrus (lemon and navel) and pomegranate, similar to our findings in 2003. Adult GWSS were also regularly collected from and observed feeding upon a wide range of non-crop weed species within and surrounding experimental orchard crops. Nymph populations were not equally represented across all perennial tree crops with increased populations collected from citrus, pomegranate, and also non-crop annual weed species. Overwintering adult GWSS were consistently collected in relatively low population densities on citrus, pomegranate, avocado, plum, peach, and non-crop annual weed species. Patterns of adult GWSS capture among the distances sampled along linear transects extending into perennial crops were dissimilar among perennial crops. The presence of Xf in a subsample of vectors collected from different perennial crops and on non-crop species is underway using a multiplex PCR protocol to differentiate genomic populations.

Last Modified: 9/2/2014
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