Thermotherapy of Strawberry Transplants as a Possible Tool for <i>Neopestalotiopsis</i> sp. Management

The introduction of transplants cryptically infected with causal agents of major diseases represents an acute challenge to strawberry growers. Neopestalotiopsis sp., responsible for Pestalotia leaf spot (PLS) and Pestalotia fruit rot (PFR), was first introduced in Florida during the 2017 to 2018 strawberry season through infected nursery material. In this study, we demonstrated that Neopestalotiopsis sp. spores did not survive temperatures of 44, 48, 52, and 56°C after 240, 60, 10, and 5 min of exposure, respectively. The thermotherapy protocol effectively reduced the inoculum of Neopestalotiopsis sp. on naturally infected and artificially inoculated strawberry transplants. Before planting, naturally infected plants and inoculated and noninoculated transplants were exposed to the thermotherapy protocol. A standard area diagram set was developed and validated to estimate the severity of PLS, improving the accuracy, precision, and reliability of ratings. On naturally infected plants, thermotherapy reduced disease incidence and severity by 49.7 to 68.8% and 82.2 to 94.6%, respectively. On artificially inoculated plants, incidence was not different between treatments, but it was reduced by 52.5% on the heat-treated, inoculated transplants. Disease severity was reduced during both seasons by 82.2 to 94.6% and 50.3 to 86.8% on heat-treated transplants that were naturally infected and inoculated, respectively. Additionally, fruit were evaluated weekly from December to mid-January for early-season yield and PFR incidence. No significant differences were observed among treatments for incidence on fruit nor for early-season yield. Thermotherapy reduced the Neopestalotiopsis sp. inoculum and could be integrated into disease management programs to reduce cryptic infections in strawberry transplants for commercial production. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .