Chilling injury and residue uptake in cold-stored 'Star Ruby' grapefruit following thiabendazole and imazalil dip treatments at 20 and 50°C

'Star Ruby' grapefruit (Citrus paradisi Macf.) were harvested from November through June and subjected to a 3-min dip in water at room temperature (20 degrees C) with or without 1200 or 200 mg/l imazalil (IMZ) or thiabendazole (TBZ) at 50 degrees C. Fruit were then stored at 2 degrees C and 90-95% relative humidity (RH) for 6 weeks and 1 additional week at 20 degrees C and approximately 80% RH to simulate a marketing period (SMP). Fruit harvested in April and June and treated with 1200 mg/l TBZ at room temperature or with 200 mg/l at 50 degrees C contained higher levels of TBZ residue than fruit picked in November and January. Fruit uptake of IMZ was not affected by harvest date. Within each date, conventional treatments with IMZ or TBZ fungicides at room temperature and treatment at 50 degrees C produced similar levels of residues in most samples. Susceptibility to chilling injury (CI) was highest in fruit harvested in November and January, lower in April and negligible in June. Water dips at 50 degrees C significantly reduced Ct, the extent depending on harvest date and storage duration. The influence of 1200 mg/l IMZ dips at 20 degrees C on CI control was not significant in most samples. Treatments with 200 mg/l IMZ at 50 degrees C produced effects in CI control similar to that of water dips at 50 degrees C. Beneficial effects were also achieved after treatment with 1200 mg/l TBZ at 20 degrees C, although its efficacy in reducing CI was markedly improved with reduced doses (200 mg/l) at 50 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.