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

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. esctdentus showed sensitivity to temperatures above 34degreesC, indicating HWT could be used as a practical way of destroying tuber-borne inoculum of this pathogen. Temperatures from 43degreesC to 64degreesC for three periods of time (10, 20 or 30 min) were applied to healthy tubers. These tubers tolerated temperatures of 55degreesC 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 55degreesC for 10, 20 or 30 min. Two field trials, applying a HWT at 53degreesC for 25 min and 55degreesC 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 53-55degreesC for 25-30 min has been recommended to control tuber-borne inoculum. (C) 2004 Elsevier Ltd. All rights reserved.