Effects of High Tunnel Soil Solarization on <i>Sclerotinia sclerotiorum</i> in the Temperate Climate of Central Kentucky

Diseases caused by <i>Sclerotinia</i> spp. can affect a wide range of plants, including vegetables, with yield losses ranging from 10 to 50%. Sclerotinia diseases can be especially problematic in high tunnels in which high-value vegetable crops are planted in early spring to extend the growing season, achieve earlier harvest, and bring higher profits. Fungicide applications and crop rotations are limited because of product application restrictions and constraints on time, crop resistance, and profitability. Soil solarization is a cultural management method that uses transparent polyethylene to raise soil temperatures via solar irradiation to kill pathogens, pests, and weeds. A 2-year study was conducted in a Kentucky high tunnel to determine the maximum temperature potential of solarization at various soil depths at different durations during different seasons and to identify temperatures at which <i>S. sclerotiorum</i> sclerotia lose viability. The experiment included solarization treatments of 2, 4, and 6 weeks and a nonsolarized control implemented in spring, summer, and fall. Sclerotia and temperature data loggers were buried at 5.1-, 10.2-, and 15.2-cm soil depths. The number of hours at which soil temperatures reached ≥40°C was greatest in summer in both years, followed by fall, and then spring. The highest average daily maximum soil temperature reached was 48.9°C, which occurred during the summer 6-week solarization in Year 1. The viability of buried sclerotia was overall lower in solarized treatments compared with nonsolarized treatments in both years. In general, the 2-week solarization treatment had a significantly higher percentage of sclerotial germination than the 4-week and 6-week treatments, which were not significantly different from one another. The viability of sclerotia was progressively higher with burial depth. In both years, sclerotial germination was significantly lower in summer compared with spring and fall.