The distribution of peach scab lesions on the surface of diseased peaches

Abstract

The aim of the study was to quantify peach scab (Fusicladosporium carpophilum) lesion distribution relative to the point of maximum lesion number on the fruit surface, the relationship between lesion count and distance from the point of maximum lesion density, and establish whether the distribution of lesions was consistent with a splash dispersed pathogen, and to assess the effect of lesion number on fruit size. Fruit of four cultivars, Jerseyqueen, Jefferson, BY07-6428r and Dixiland were collected and the fruit (assumed spherical) sliced taking three horizontal planes across the axis from the point of maximum disease, such that each horizontal zone (Z1-Z4) had the same vertical height, and thus equal surface areas. Lesion counts were analysed using general linear modeling with a Poisson distribution and a log-link function. Zones on the fruit had different numbers of lesions (P 90° to the peduncle. This pattern of disease is consistent with observations of the splash-borne nature of conidia, with the most exposed, easily wetted, uppermost portion of fruit developing most disease.