Greenhouse atmospheric environment and grey mould (Botrytis cinerea) of forest nursery seedlings
Date
1986
Authors
Peterson, Michael James
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Abstract
Microclimatic data were collected in the vicinity of Douglas-fir seedlings grown in polyethylene and fibreglass-covered greenhouses operated by Canadian International Paper at Saanichton on southern Vancouver Island. Coinciding with these observations, airborne Botrytis cinerea spores were trapped above each seedling canopy. Environmental parameters observed above and below the canopy in each greenhouse included light intensity and spectral quality, air temperature, humidity and vapour pressure deficit.
Light intensity in all wavelengths was highest in the polyethylene-covered greenhouse. Beneath each seedling canopy, light intensities in wavelengths that stimulate (300-420 nm) or inhibit (430-490 nm) B. cinerea sporulation, were too low to be effective.
A diurnal periodicity of increased spore concentrations between 04:00 and 20 :00 was observed in each greenhouse. Airborne spore concentrations were significantly higher in the fibreglass greenhouse following an outbreak of grey mould.
Greenhouse covering had a minimal direct effect on grey mould of container- grown Douglas-fir seedlings. Restricted air movement created by a denser seedling canopy in the fibreglass-covered greenhouse contributed to increased humidities and the presence of longer intervals when conditions were ideal for spore germination. This is considered to be the most important control of the occurrence of grey mould on Douglas-fir seedlings.
After its establishment, grey mould intensified within the fibreglass greenhouse . Increased airborne spore densities coincided with the application of overhead irrigation water. Multiple regression analysis was made using LOG10 of spore density versus climatic elements in the fibreglass greenhouse for September and October during those times the irrigation water was on. Canopy humidity and ambient vapour pressure deficit were included in the model. Ambient vapour pressure deficit was the most influential factor with regard to increased spore density.