Spatial pattern analysis of strawberry leaf blight in perennial production systems

Area of Science:

• Plant Pathology
• Agricultural Science
• Spatial Statistics

Background:

• Strawberry leaf blight, caused by Phomopsis obscurans, is a significant disease affecting commercial strawberry production.
• Understanding the spatial patterns of disease incidence is crucial for effective disease management strategies.

Purpose of the Study:

• To quantify the spatial pattern of Phomopsis leaf blight incidence in commercial strawberry fields.
• To analyze the heterogeneity and spatial correlation of disease at leaflet and leaf levels.
• To evaluate different statistical methods for analyzing disease spatial patterns.

Main Methods:

• Sampling of leaflets and leaves in commercial strawberry fields in Ohio over two years.
• Application of beta-binomial distribution and heterogeneity indices (index of dispersion, C(alpha) test, theta parameter).
• Analysis of spatial association using autocorrelation coefficients, runs analysis, and spatial analysis by distance indices (SADIE).

Main Results:

• Overdispersion was detected in approximately 94% of data sets at the leaflet level and 36% at the leaf level.
• Disease heterogeneity was a function of incidence, with minimal influence from cultivar, time, or location.
• Significant nonrandom spatial arrangements were found in 9-22% of data sets, characterized by small, loosely aggregated clusters.

Conclusions:

• Phomopsis leaf blight incidence is primarily characterized by small, aggregated clusters of diseased leaflets within sampling units.
• The beta-binomial distribution and SADIE analysis are effective tools for analyzing disease spatial patterns.
• Effective disease management may require strategies that address localized disease hotspots.