Wound infection of plum fruit by airborne conidia of Monilinia laxa

Abstract

Infection of non-wounded and freshly wounded detached plum fruit by airborne Monilinia laxa conidia on dry, humid and wet plum fruit surfaces, and by conidia and germlings that had been established on fruits under these wetness regimes, was investigated. Plum fruit (cv. Laetitia) were dusted with dry conidia in a settling tower at pit hardening, 2 weeks before harvest, at harvest and after 28 days cold storage. Non-wounded immature and mature fruit remained mostly asymptomatic, whereas non-wounded cold-stored fruit decayed readily. Wounding drastically increased infection by airborne conidia. Immature fruitswere less susceptible to wound infection by airborne conidia than mature fruits. Conidia that were dispersed freshly were more successful in infecting fresh wounds than conidia that were deposited, or germlings that established, on fruits 4 days prior to wounding. This decrease in infectivity was especially pronounced on humid-incubated fruit and on wet-incubated fruit. This study clearly showed that in order to reduce the incidence of brown rot, inoculum levels on fruit approaching maturity should be reduced by sanitary practices and fungicides. Furthermore, it is essential to protect fruit, especially near-mature fruit, from being wounded.