SOIL SOLARIZATION: A USEFUL TOOL FOR CONTROL OF VERTICILLIUM WILT AND WEEDS IN EGGPLANT CROPS UNDER PLASTIC IN THE PO VALLEY
G. Tamietti, D. Valentino
To develop strategies integrated with or alternative to chemicals for controlling pests, weeds and pathogens of vegetables, solarization and semi-solarization were tested in four consecutive years against Verticillium dahliae Kleb. on eggplants and weeds under plastic in the Po Valley, Piedmont, Italy. The temperature required for V. dahliae inactivation as a function of exposure time, and the number of days needed for effective solarization were also investigated. Treatment at 38- 45°C for various periods were lethal to V. dahliae microsclerotia. The time to attain LD90 was 21, 97, 275, and 324 h respectively at 45, 42, 40, and 38°C. Temperatures and times required to kill 90% of the propagules were significantly correlated (R2 = –0.9437), with a regression curve in which lethal temperature was a natural log function of exposure time. Compared with the control, semi-solarization and solarization increased the soil temperature by 8.1-10.7°C and 14.4-16.8°C respectively, at 25 cm depth. The laboratory tests suggested that in Piedmont the effective mulching period may be shorter than 45 days. Semi-solarization and solarization reduced Verticillium wilt severity by 35-48% and 89- 98%, but their effectiveness was lowered by subsequent deep tillage. Eggplant yield was consistently higher in solarized than in control soil, and intermediate in semisolarized soil. Solarization reduced weeds by 97%, whereas semi-solarization had little or only moderate herbicidal effect.