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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Plant Pathology Research » Research » Publications at this Location » Publication #331457
Title: Analysis of the spatial pattern of strawberry angular leaf spot in California nursery production

Author
item GIGOT, CHRISTOPHE - University Of California
item Turechek, William
item MCROBERTS, NEIL - University Of California

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2017
Publication Date: 7/16/2017
Citation: Gigot, C., Turechek, W., McRoberts, N. 2017. Analysis of the spatial pattern of strawberry angular leaf spot in California nursery production. Phytopathology. 107:1243-1255. https://doi.org/10.1094/Phyto-07-16-0275-R.
DOI: https://doi.org/10.1094/Phyto-07-16-0275-R

Interpretive Summary: Angular leaf spot (ALS) is a common bacterial disease of strawberry. It is a major concern for nurseries that export plants to Europe. The spatial pattern of disease is an ecological property whose characteristics offer insight into pathogen source, mode(s) of dissemination, and how crop management practices affect epidemic development. An understanding of the spatial pattern of ALS would allow nursery growers to make informed decisions in disease management. The spatial pattern of ALS was characterized over two growing seasons at several locations in California. ALS exhibited a high degree of aggregation, particularly between plants within the same planting row. This suggests that recurrent crop operations during the growing season play a significant role in ALS spread, and that these recurrent practices may need to be altered to improve disease control.

Technical Abstract: Xanthomonas fragariae is a bacterium that causes angular leaf spot of strawberry. In California, angular leaf spot (ALS) is a common disease in strawberry nursery production, and a major concern for nurseries wishing to export plants. The spatial pattern of disease is an ecological property whose characteristics offer insight into pathogen source, mode(s) of dissemination, and how crop management or husbandry practices affect epidemic development. An understanding of the spatial pattern of ALS would allow nursery growers to make informed decisions in disease management. Ninety seven field assessments of disease incidence were performed at different nursery locations in 2014 and 2015 to quantify ALS spatial pattern under commercial conditions. Both point-pattern and geostatistical statistical procedures were used to analyze the data. The spatial pattern of ALS was characterized by a high degree of heterogeneity, as indicated by high median values of the beta-binomial distribution's theta parameter, 0.643, and the index of dispersion of 4.218. The binary power law provided a robust description of the data with estimated slope and intercept parameters significantly (P < 0.001) greater than 1 and 0, respectively. Spatial Analysis by Distance IndicEs (SADIE) detected significant nonrandom spatial arrangements for 64% of the data sets. Analysis of directional disease spread showed a strong spatial association between sampling units along the same planting row. This suggests that recurrent crop operations during the growing season would play a significant role in ALS spread that should be taken into account to improve disease control.