Risks for infection of strawberry plants with an aerosolized inoculum of Xanthomonas fragariae

J.M. van der Wolf*, A. Evenhuis, P. Kastelein, M.C. Krijger, V.Z. Funke, W. van den Berg, A.F. Moene

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Xanthomonas fragariae is the causative agent of angular leaf spot of strawberry, a quarantine organism in plant propagation material in the European Union. Field experiments were conducted to assess the risks for infection of strawberry plants through dispersal of an aerosolized inoculum. In practice, pathogen aerosols can be formed during mowing of an infected crop or by water splashing on symptomatic plants during overhead irrigation or rain. In our experiments, aerosols were generated by spraying suspensions of X. fragariae with a density of 108 cfu ml−1 or water under pressure vertically up into the air. In strawberry plants (cv Elsanta) placed at 1.3, 5 and 10 m distance downwind from the spray boom, infections were found, as evidenced with a combination of dilution–plating and molecular techniques, but more frequently in plants wetted prior to inoculation than in plants kept dry. A logarithmic decrease in infection incidence was found with the distance to the inoculum source. Symptomatic plants were found up to 5 m distance from the inoculum source. No infected plants were found in plants placed 4 m upwind or treated with water. In glasshouse studies, it was shown that under conditions favorable for disease development, spray-inoculation of strawberry plants with estimated densities of X. fragariae as low as 2000 cfu per plant were able to cause symptoms both in cv Elsanta and cv Sonata. Results indicate that there is a considerable risk on infections of strawberry plants exposed to aerosolized inoculum.

Original languageEnglish
Pages (from-to) 711–722
JournalEuropean Journal of Plant Pathology
Volume152
Issue number3
Early online date31 May 2018
DOIs
Publication statusPublished - Nov 2018

Keywords

  • Air sampling
  • Angular leaf spot
  • Fragaria x ananasa
  • Infection thresholds
  • Particle counters
  • TaqMan assay

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