Journal of Phytopathology. 2020;00:1–9. wileyonlinelibrary.com/journal/jph | 1 © 2020 Blackwell Verlag GmbH 1 | INTRODUCTION Penicillium digitatum causes green mould, which is the main postharvest rot in citrus, damaging the fruits and causing major economic losses. P. digitatum infects the fruits through wounds caused by insects, during harvest and postharvest processes, and transport (Perez et al., 2017). The infection begins as a watery spot on the fruit rind, and after that, under appropriate tempera- ture and humidity conditions, this spot turns into a white mycelium covered with olive-coloured spores (Costa et al., 2019, Erasmus et al., 2015). The green mould in postharvest citrus has been mainly managed using a synthetic fungicide. Currently, the most effective fungicide registered for controlling green mould is imazalil (Erasmus et al., 2015), but its intensive use caused resistant isolates to develop. Moreover, the risks for human and environmental health and pub- lic concern about chemical toxicity amplified the necessity to de- velop alternatives for controlling postharvest rots (Costa et al., 2019; Received: 9 December 2019 | Revised: 28 June 2020 | Accepted: 29 June 2020 DOI: 10.1111/jph.12932 ORIGINAL ARTICLE Chitosan and hot water treatments reduce postharvest green mould in ‘Murcott’ tangor Yasmim Cristina Rodrigues Da Silva 1 | Raysa Maduro Alves 1 | Bárbara Marçon Pereira da Silva 2 | Ilana Urbano Bron 3 | Patrícia Cia 3 1 Agricultural Engineering Post Graduation Program, Universidade Estadual de Campinas, Campinas, Brazil 2 Tropical and Subtropical Agriculture Post Graduation Program, Instituto Agronômico, Campinas, Brazil 3 Ecophysiology and Biophysics Center, Instituto Agronômico, Campinas, Brazil Correspondence Patrícia Cia, Instituto Agronômico, Av. Barão de Itapura, 1.481, Campinas, SP 13020-902, Brazil. Email: pcia@iac.sp.gov.br Abstract This study aims to evaluate the efficacy of hot water and chitosan treatments to control green mould caused by Penicillium digitatum in 'Murcott' tangor. P. digitatum conidial germination and mycelial growth were evaluated in assays in vitro to verify whether chitosan (0.5, 1 and 2%) or hot water (45, 50, and 55°C, for 30 s, 1, 2, and 5 min) acts directly on fungus development. In vivo assays consisted of inoculat- ing the fruit with P. digitatum (10 5 conidia ml −1 ) 4 hr before the chitosan and hot water treatments. Subsequently, green mould incidence and severity were evaluated in fruits stored at 25°C/80% RH for 4 days. Also, treatments combining chitosan and hot water were investigated for controlling green mould and the effect on post- harvest quality of fruit stored at 5°C/90% RH. The results showed that P. digitatum conidia germination and mycelial growth were significantly reduced by the hot water treatments especially at 50°C/5 min and 55°C/2 or 5 min in the first case and 50 and 55°C/5 min in the second. These two treatments, when applied alone, 1 min dip- ping in 2% chitosan or hot water at 50°C/5 min, significantly reduced green mould development in fruit kept at 25°C/80% RH or refrigerated. However, the hot water dip combined with chitosan did not improve green mould control on ‘Murcott’ tangor at room temperature or under refrigeration. Besides, chitosan and hot water did not impair fruit quality. Thus, chitosan and hot water could be an alternative to synthetic fungicides to control green mould in citrus while also contributing to a decrease in the postharvest losses of ‘Murcott’ tangor. KEYWORDS alternative control, Citrus, fruit quality, Penicillium digitatum