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 Botryt is cinerea in a gerbera crop in two glasshouses (100 m2 and 350 m2) wa s studied during 18 months in 1988 and 1989. Conidia of B. cinerea wer e caught in simple spore traps consisting of agar in Petri dishes plac ed in a regular pattern at three different heights in the glasshouse a nd counted as colonies, after incubation. Lesions due to conidial infe ction were counted on gerbera petals. The horizontal and vertical dist ribution 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 suffi cient for efficient monitoring of B. cinerea in a glasshouse.