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Dispersal of Botrytis cinerea conidia in raspberry fields

Odile Carisse: Agric & Agri-Food Canada

<div>Raspberry fruit rot, caused by <em>Botrytis cinerea </em>Pers. ex Pers., is one of the most important fruit diseases of raspberry. Currently, the disease is controlled with applications of fungicides. The improvement of cultural methods for disease management should lessen this dependence on fungicides. However, such improvements would not be possible without knowledge of inoculum sources and dispersal of the pathogen. Dispersal of airborne conidia and incidence of Botrytis fruit rot were monitored at two raspberry plantings during three successive years with meteorological data. The concentrations of conidia were monitored using a 7-day volumetric sampler and rotating-arms samplers.The number of <em>B. cinerea</em> conidia in air samples was determined with a real-time qPCR assay. Dispersal of airborne conidia was assessed at 0.5, 1.0, 1.5, 2.0, 4, and 8 m from a fixed point source of inoculum with rotating-arms samplers placed at 0.45, 0.90, and 1.35 m from the ground. Each year, the experiment was conducted four times. The coefficient of correlation between the volumetric and rotating-arms samplers placed at 45, 90, and 135 cm from the ground was significant; and a diurnal pattern of conidial release was observed. During the pre-bloom and bloom period, conidia dispersal gradient (log (conidia/m<sup>3</sup>) vs distance in m) showed significant flattering at a distance of more than 2 m from the inoculum source. However, near or at harvest no significant dispersal gradients were observed.</div>