Prevention of Phytophthora root rot in Gerbera by increasing copper ion concentration in the nutrient solution

Abstract

Increased copper concentration in the nutrient solution was used as a means for reducing the severity of root rot caused by Phytophthora cryptogea in Gerbera jamesonii in three experiments. Plants were grown in pots on ebb-and-flow benches with separate systems for recirculating nutrient solutions. Eight nutrient solutions with two concentrations of copper ions (0.07 and 0.28 ppm), two electrical conductivity values (1.5 and 2.2 mScm-1), and two iron sources (FeHEEDTA or FeSO4) were combined in a factorial design. Plants were inoculated with zoospores of P. cryptogea via the recirculating nutrient solution. Disease incidence was significantly reduced in inoculated plants grown on nutrient solution with 0.28 ppm copper compared with 0.07 ppm copper, when FeSO4was introduced as the iron source. No effects of increased copper concentration was observed when iron was added as FeHEEDTA. The change in electrical conductivity from 1.5 to 2.2 mScm-1 without changing the Cu2+ concentration did not influence the disease severity in these experiments. The results suggest that increased copper ion concentration in the nutrient solution could be a component of disease management strategy for ebb-and-flow systems. Possible management of the cupric ion concentration in the nutrient solutions is discussed.