EVALUATION OF SOIL SOLAR HEATING FOR CONTROL OF DAMPING-OFF FUNGI IN 2 FOREST NURSERIES IN FRANCE

Field experiments were carried out at two different forest nurseries d uring the summer of 1994 to examine the efficacy of soil solarization for the control of damping-off. Both soils hosted Pythium spp., Fusari um spp. and Rhizoctonia solani as damping-off agents. Soil samples fro m solarized, steamed, fumigated and untreated plots were periodically collected and assayed for soil infectivity. Solarization with a double layer of polyethylene film was as effective as steaming or fumigation in reducing soil infectivity in the uppermost layer. During July the temperature of covered beds rose as high as 50 degrees C at a soil dep th of 5 cm. The method achieved good control of Pythium spp., the main cause of damping-off at both nurseries, whereas Fusarium spp. were mo re tolerant. The association of Trichoderma spp. with a reduction of s oil infectivity at the last sampling date strongly suggested that bioc ontrol processes were induced after solarization. Soil solarization pr ovides a suitable method for control of damping-off.