Doenças pós-colheita em laranja 'Pêra' produzida em sistema orgânico e convencional e resistência de Penicillium digitatum a fungicidas

Abstract

Postharvest diseases may be responsible for significant losses to citrus growers. This study aimed to: a) characterize the postharvest diseases in 'Pêra' oranges from organic and conventional crops, with or without postharvest treatment with imazalil, marketed in CEAGESP; and b) detect the presence of Penicillium digitatum isolates resistant to fungicides in fruits with green mold. Fruits were kept in a humid chamber for 24 hours and for additional 13 days at 25°C and 85% RH. The disease incidence was visually evaluated at every 2-3 days. The presence of P. digitatum resistant to the fungicides was assessed based on mycelial growth on potato-dextrose-agar medium added of the fungicides thiabendazole (10 mg.L-1) and imazalil (1 mg.L-1). Fruits treated with imazalil had lower incidence (5.4%) of postharvest diseases, while fruits from organic crop had the highest incidence (25.2%). The main postharvest diseases were green mold in fruits produced in the conventional system and Lasiodiplodia and Phomopsis stem-end rot in organic fruits. The relative frequency of P. digitatum isolates resistant to the fungicide thiabendazole was lower in organic fruits, while the frequency of P. digitatum isolates resistant to imazalil and the mixture thiabendazole+imazalil was higher in fruits that received postharvest treatment with imazalil.