Combined efficacy assessment of soil solarization and bio-fungicides for management of Sclerotinia spp. in lettuce (Lactuca sativa L.)

Abstract

White mould: Sclerotinia spp., is the lettuce main disease in the Colombian high Andes. It causes yield losses of up to 70% and is primarily managed with chemical fungicides, while alternative control strategies are poorly used. Soil solarization and a set of chemical and bio-fungicides for Sclerotinia management efficacy in lettuce, were determined. Biofungicides included different doses of Allium sativum and Matricaria recutita extracts and Trichoderma koningiopsis suspensions. The fungicide procymidone was also evaluated. Field trials included single or combined treatments application. Non-linear modelling and AUDPC were employed to determine the efficacy of management strategies. Both S. sclerotiorum and S. minor caused white mould, being S. minor the dominant species. Solarization significantly lowered Sclerotia population in the upper soil layers and consequently lowered disease incidence. Highest levels of Sclerotinia control were achieved with solarization, particularly in combination with procymidone or T. koningiopsis (79.08% and 41.50% disease reduction, respectively). Non-linear modeling of disease epidemic progress curve proved a valuable alternative to AUDPC, which allowed multiple disease development parameters estimation and indirectly the efficacy of management strategies. This work should help the advance of environmentally-sound management of Sclerotina spp. in lettuce, under the highly specific growing conditions of the high Andes.