THE EFFECT OF RELATIVE HUMIDITY ON SPORE GERMINATION OF PEAR DECAY FUNGI AND D’ANJOU PEAR DECAY

The effect of high relative humidity (RH) on conidial germination of five pear decay fungi was studied at -1.1, 10, and 20°C. At 100% RH, Mucor piriformis, Botrytis cinerea, Pezicula malicorticis, Penicillium expansum, and Phialophora malorum germinated at -1.1, 10, and 20°C. At -1.1°C, no germination occurred at 97% RH, and only B. cinerea germinated at 99% RH. At 10°C, no germination occurred at 90% RH, and only P. expansum germinated at 95% RH. At 20°C, no germination occurred at 80 or 90% RH. Days required for germination of fungal spores at -1.1°C were as follows: B. cinerea – 14, P. malorum – 21, P. malicorticis – 42, M. piriformis – 45, P. expansum – 51. When wounded d’Anjou pears were inoculated with conidia of the five fungi and placed at 97, 99, or 100% RH at -1.1°C, B. cinerea, P. expansum, and P. malicorticis caused decay at all RH levels.
M. piriformis and P. malorum decay occurred only at 100% RH. The RH in commercial bins of d’Anjou pears during storage at -1.1°C was 98 to 100% RH, and free water may be present due to fluctuating temperature.

III International Symposium on Pear Growing

R.A. Spotts, B.B. Peters

https://doi.org/10.17660/ActaHortic.1982.124.10