Influence of day/night humidity and cation ratios and concentration in the nutrient solution on incidence of Didymella bryoniae in glasshouse cucumbers.

Abstract

The incidence of the disease on plants and fruits decreased with a lower 24 h av. RH in the range 80-87%. An increase in the electrical conductivity (EC) level of the nutrient solution from 2.5-5.0 dS/m (25 degrees C) decreased the number of diseased leaf axils at a Ca concn of 1.5 mmol/litre by 41%, but had no effect at a Ca concn of 4.5 mmol/litre. An increase in Ca concn from 1.5-4.5 mmol/litre decreased the number of diseased leaf axils at an EC level of 2.5 dS/m by 26%, but had no effect at an EC level of 5.0 dS/m. Changes in EC and Ca concn had no effect on the number of fruits with internal rot. It is concluded that to optimize disease control, high RH, low EC level and low Ca concn in the nutrient solution should be avoided. (Abstract retrieved from CAB Abstracts by CABI’s permission)