Solar Heating by Polyethylene Mulching for the Control of Diseases Caused by Soil-Borne Pathogens

Irrigated soils in the hot Bet-Shean and Jordan Valley regions were mulched with transparent 0.03-mm polyethylene sheets during the months of July or August, and soil temperatures were thereby increased. Different types of inocula of Verticillium dahliae and Fusarium oxysporum f. sp. lycopersici were buried in mulched and nonmulched soils at various depths, recovered after certain time intervals, and their populations were estimated. After two weeks under polyethylene sheets, V. dahliae was eliminated at depths of 0 to 25 cm. The population of F. oxysporum f. sp. lycopersici at the depth of 5 cm was reduced by 94 to 100%; at 15 cm, 68 to 100%; and at 25 cm, 54 to 63%. Maximal temperatures in the mulched soils were 49 to 52 C and 42 C at depths of 5 and 15 cm, respectively. At 50 C, soil fungistasis to Fusarium was partially nullified. Two field experiments with eggplant and one with tomato showed, that mulching with polyethylene sheets prior to planting reduced Verticillium wilt by 25 to 95%, controlled weeds, improved plant growth and stand, and increased yield. This method of control using plastic material is less costly than fumigation, is nonhazardous, and leaves no residues. It is suggested that biological as well as thermal control may take place during soil mulching.