HORIZONTAL AND VERTICAL-DISTRIBUTION OF AIRBORNE CONIDIA OF BOTRYTIS-CINEREA IN A GERBERA CROP GROWN UNDER GLASS

The horizontal and vertical distribution of airborne conidia of Botrytis cinerea in a gerbera crop in two glasshouses (100 m2 and 350 m2) was studied during 18 months in 1988 and 1989. Conidia of B. cinerea were caught in simple spore traps consisting of agar in Petri dishes placed in a regular pattern at three different heights in the glasshouse and counted as colonies, after incubation. Lesions due to conidial infection were counted on gerbera petals. The horizontal and vertical distribution of conidia of B. cinerea in a gerbera crop grown under glass was fairly uniform in both distinct glasshouses. Conidia of B. cinerea trapped in a glasshouse can originate from sources inside and outside the glasshouse. No significant interaction was found between location and time for the colony counts and for the log transformed (ln(N + 1)) lesion counts. The results of this study suggest that spore trapping at one height and at a limited number of locations and dates is sufficient for efficient monitoring of B. cinerea in a glasshouse.