Spatial Pattern of Verticillium Wilt in Commercial Mint Fields

Area of Science:

• Plant Pathology
• Agricultural Science
• Spatial Statistics

Background:

• Verticillium wilt, caused by Verticillium dahliae, is a significant disease affecting commercial mint production.
• Understanding the spatial distribution of Verticillium wilt is crucial for effective disease management strategies.

Purpose of the Study:

• To characterize the spatial patterns of Verticillium wilt in commercial mint fields using advanced spatial analysis techniques.
• To quantify disease aggregation, focus size, and spread over time within perennial mint crops.

Main Methods:

• Spatial analysis methods, including variance-to-mean ratio, doublets, and runs analyses, were applied to data from 10 commercial mint fields in Washington.
• Disease incidence was assessed using 0.76-by-0.76-m quadrats within randomly selected field sections.
• Proximity index was used to evaluate the compactness of disease foci.

Main Results:

• The variance-to-mean ratio indicated aggregation of diseased stems within quadrats, with clustering generally higher within than across mint rows.
• Total number of wilt foci and their mean size increased over successive years in a repeatedly sampled field.
• Mean focus size was larger within crop rows compared to across rows in most sampling occasions, with a proximity index indicating highly compacted disease foci.

Conclusions:

• Spatial analysis methods effectively described and quantified Verticillium wilt patterns in commercial mint.
• Verticillium wilt spreads during the perennial mint crop cycle, with secondary spread likely originating from sources other than pre-plant soil inoculum or infected rhizomes.