Screening of fungicides effective against tomato Nectria blight and determination of their optimal application timing

Abstract

To establish an effective strategy for the chemical control of tomato Nectria blight, caused by Haematonectria ipomoeae, we evaluated the efficacy and timing of fungicide application to suppress infection through leaf-scar wounds. In vitro assays, seedling tests, and field trials showed that fludioxonil, pyribencarb, mandestrobin, ipflufenoquin, and a pyraclostrobin–boscalid mixture provided high control efficacy, with a protective value exceeding 70 (70% disease suppression compared with the untreated control) under field conditions. Infection markedly decreased when plants were inoculated ≥3 days after leaf removal, suggesting that wound healing at leaf scars restricted pathogen entry. These findings indicate that fungicide application within about 3 days after leaf removal effectively prevents initial infection and contributes to improved control of tomato Nectria blight.