Survival of plant pathogens under structural solarization

Structural solarization of greenhouses is a nonchemical sanitation procedure. The method involves dry heating, since maximal temperatures may exceed 60°C and consequent relative humidity (r.h.) is low (ca 15%), under fluctuating temperature and r.h. regimes. Thirty-five structural solarization experiments were performed over 7 years, testing one bacterial and five fungal plant pathogens. Various aspects of pathogen thermal inactivation under this method were studied. Thermal inactivation of the various pathogens differed according to the organism and inoculum form. Sensitivity to heat was highest with Clavibacter michiganensis subsp. michiganensis and lowest with Fusarium oxysporum f.sp. radicis-lycopersici inoculum in dry infected tomato stems, with ED₈₀ values of 7 and 47 days, respectively; intermediate values were obtained for Pythium sp., F. oxysporum f.sp. melonis, F. oxysporum f.sp. basilici and Sclerotium rolfsii. The maximal ambient temperatures were in the range of 28.2° to 33.1°C. Structural solarization for sanitation can be a useful component of integrated pest management in greenhouses.