Synergistic strategies for sustainable crop protection: harnessing soil solarization and biofumigants to combat damping-off pathogens in Solanaceous vegetable crops

Field experiments were conducted in the summers of 2019 and 2020 to study the effects of soil solarization, biofumigants derived from cauliflower leaves and combinations of those treatments on population densities of soil pathogens Pythium ultimum, Fusarium oxysporum, Rhizoctonia solani, and Sclerotium rolfsii causing damping-off disease in major solanaceous crops. Nylon mesh bags containing mass culture of P. ultimum, F. oxysporum, R. solani, and S. rolfsii were buried underneath the soil at 5 and 10 cm depth. Soil solarization was performed over a 40-day period using thin transparent polythene sheet of 25 µm (100 gauge) thickness. Maximum soil temperatures recorded at depth of 5 cm were 41.8 °C in solarized soil, respectively; this temperature was 5.4 °C higher than in corresponding non-solarized plot. These nylon sieve bags containing culture of the different pathogens were retrieved after 15, 30 and 40 days of solarization and brought to the laboratory to find out the viability of the pathogens. Integration of soil solarization with cauliflower leaves as soil amendment for the period of 40 days at 5 cm soil depth was found most effective in reducing the viability of P. ultimum, F. oxysporum, R. solani, and S. rolfsii to 5.3, 2.6, 4.6, and 3.6% in comparison with 92.6, 77.3, 83.3, and 80.3 in control, respectively. With the increase in the duration of soil solarization from 15 to 40 days, the potential of the pathogens to cause the disease reduced significantly at 5 cm soil depth and incidence of the damping-off reduced from 63.3 to 16.6% in tomato; 66.6 to 20.0% in chilli and 70.0 to 23.3% in capsicum. Through this integrated approach, the viability of soil-borne pathogens can be minimized, thereby improving the overall plant health.