INFLUENCE OF VENTILATION TEMPERATURE AND LOW VENTILATION RATES ON INCIDENCE OF DIDYMELLA BRYONIAE IN GLASSHOUSE CUCUMBERS

Depending on whether the plants were inoculated or not and on the period after inoculation the number of lesions on the main stem was 0.5 to 3 times higher at a ventilation temperature of 26°C than at one of 23°C when the heating temperature was set at 19/21°C (night/ day). Internal fruit rot occurred two to three times more frequently at a ventilation temperature of 26°C than at one of 23°C. In another year when heating temperature was 19°C (night and day) disease incidence on the main stem did not differ at a ventilation temperature of 23°C and one of 26°C, but internal fruit rot occurred three to four times more frequently at a ventilation temperature of 26°C.

The use of a fan during 2 h in the early morning at a ventilation temperature of 26°C did not or hardly decrease the disease incidence on plants and fruits. The use of a fan during daylight at a ventilation temperature of 26°C sometimes reduced plant infection but fruit infection occurred even more frequently in one experiment.

Inoculation of the plants reduced fruit production by 0 to 20%, depending on growing and climatic conditions.

The influence of the ventilation regimes on the development of a natural infection of Botrytis cinerea was about the same as it was on the development of D. bryoniae on plants not inoculated with D. bryoniae.

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