ARS | Publication request: Phenology of Xylella fastidiosa and Draeculocephala minerva in California almond nurseries: an assessment of plant vulnerability to almond leaf scorch disease

Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: November 2, 2011
Publication Date: December 13, 2011
Citation: Krugner, R. 2011. Phenology of Xylella fastidiosa and Draeculocephala minerva in California almond nurseries: an assessment of plant vulnerability to almond leaf scorch disease. CDFA Pierce's Disease Control Program Research Symposium, Dec 15-18, 2011, Sacramento, California. p.29.

Technical Abstract: Management of a plant disease requires knowledge of all possible infection pathways. Almond leaf scorch disease (ALSD) is caused by the xylem-limited bacterium Xylella fastidiosa, which is transmitted by several species of leafhoppers. The objectives of this research were to elucidate the fate of bacterial inoculations in almond nursery plants; to elucidate patterns of insect vector population dynamics and movement relative to host plant assemblages in habitats surrounding commercial nurseries; and to investigate the temporal distribution of X. fastidiosa-infected plants in those habitats. In an experimental nursery, disease incidence was markedly affected by rootstock type. Prior to budding, nursery plants were immune from bacterial infection if using Nemaguard roostock. After budding with a susceptible scion, plants were vulnerable to infection regardless of the rootstock type. Surveys in commercial nurseries revealed that only habitats with permanent grass cover sustained vector populations throughout the season. A total 87 plant samples tested positive for X. fastidiosa (6.3%) using ELISA, with a higher number of X. fastidiosa-infected plants found in weedy alfalfa fields than in other habitat types. Among X. fastidiosa-positive plants, 33% were winter annuals, 45% were biannuals or perennials, 22% were summer annuals. Collectively, these findings identified an infection pathway other than primary spread that may occur in established orchards.