Control of Dematophora necatrix on Cyperus esculentus tubers by hot-water treatment

Abstract

Dematophora necatrix causes a tuber rot of cultivated Cyperus esculentus in eastern Spain. The disease is spread through infected tubers. To overcome this problem, the use of a hot-water treatment (HWT) of C. esculentus tubers was studied. Isolates of D. necatrix from C. esculentus showed sensitivity to temperatures above 34°C, indicating HWT could be used as a practical way of destroying tuber-borne inoculum of this pathogen. Temperatures from 43°C to 64°C for three periods of time (10, 20 or 30 min) were applied to healthy tubers. These tubers tolerated temperatures of 55°C from 10 to 30 min without a reduction in sprouting. Recovery of D. necatrix was not possible by isolations on potato dextrose agar +500 mg l −1 of streptomycin sulfate from internal fragments of affected tubers treated at 55°C for 10, 20 or 30 min. Two field trials, applying a HWT at 53°C for 25 min and 55°C for 25 min, respectively, on infected planting material, showed normal plant development without reduction in yield and a good control of the disease. HWT at 53–55°C for 25–30 min has been recommended to control tuber-borne inoculum.