USE OF SOIL SOLARIZATION FOR CONTROLLING BACTERIAL CANKER OF TOMATO IN PLASTIC HOUSES IN GREECE

Soil solarization provided effective control of bacterial canker of tomato in plastic houses. Trials in plastic houses in Preveza County, Greece, during the period 1990-1992 showed that soil solarization (approximately 6 weeks of soil mulching with transparent polyethylene sheets) drastically reduced disease incidence throughout the cropping season. In contrast, soil fumigation with a recommended rate of methyl bromide (70 g/m(2)) was ineffective. Both wild-type and antibiotic-resistant strains of Clavibacter michiganensis subsp. michiganensis, growing on Nutrient Agar Glycerol (NAG) medium within covered and screwed vials and embedded at various soil depths (5, 15 or 25 cm) before soil solarization, were studied. Weekly sampling of bacteria during treatment showed a sharp decline of populations in the solarized soil compared to the non-treated control plots 4-6 weeks after soil tarping. Populations of marked strains infiltrated into tomato stem segments and buried in the soil decreased significantly after 5-6 weeks of solarization compared to non-treated control plots. The data presented here suggest that soil solarization is useful for the control of bacterial canker of tomato in plastic houses in Greece.