Epidemiology of Monilinia laxa, the causal agent of blossom blight in almond orchards within the Ebro Valley

Abstract

BACKGROUND: Almond blossom blight, caused by Monilinia spp., is a notable fungal disease associated with intensified cropmanagement practices. In this study, we aimed to investigate the epidemiology of Monilinia spp. on almonds in two orchardsin the Ebro Valley, with a focus on (i) primary inoculum sources through sampling of affected mummified fruiting structuresfrom trees and the ground before blooming; (ii) secondary inoculum sources postblooming; and (iii) disease dynamics through-out the season in relation to meteorological data.RESULTS: Monilinia laxa was the primary species affecting almonds in the Ebro Valley. Furthermore, early-stage mummifiedfruiting structures frequently adhered to branches (3.8 log conidia/mummified fruiting structure), whereas late-stage mummi-fied fruiting structures were predominantly found on the ground. Additionally, cankers present before blooming (6.0 × 102 and1.4 × 103 conidia/canker) served as primary inoculum sources. Inoculum incidence and concentration were significantly higherin late-stage fruits (50–100%, 8.5 × 103–2.5 × 105 conidia/plant organ) than those in flowers (20–30%, 2.0–4.0 × 103 conidia/plant organ) or those in postblooming cankers (1.0 × 102–1.8 × 10 3 conidia/canker). Infection dynamics of blossom blight inboth orchards peaked during the last third of April under favorable meteorological conditions, specifically within the 10 dayspreceding the assessments. Significant correlations were found between infections progression and meteorological parame-ters, including temperature, relative humidity, rainfall and leaf wetness.CONCLUSION: These findings provide critical insights into sustainable disease management practices and the optimal timing ofprotective measures against blossom blight.© 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.