No abstract

Relation between fruit wounding. Application of wax either waxing and development of rots in citrus fruit during storage. Plant Disease 69:869-870. before or after inoculation suppressed the incidence of the mold rots (Fig. 2). Waxing of citrus fruit reduced mold rots caused by Penicillium digitatum and P. italicum and Similar results were found for Valencia increased stem-end rots and internal core rot caused by Alternaria citri, Diplodia natalensis, and

Postharvest treatments with thiabendazole (TBZ) and benomyl reduced the incidence of chilling injury (Cl) in grapefruit (Citrus paradisi, MacFadyen) as expressed by peel pitting. The effect persisted during prolonged storage at 2, 5 and 8°C. Thiabendazole was more effective than benomyl. The effectiveness of both TBZ and benomyl in water suspension increased when followed by waxing, but the greatest reduction in Cl was obtained with the chemicals incorporated in the wax coating. The effect of TBZ was enhanced by increasing concentration and residues, while the effect of benomyl did not change with concentration. Both chemicals were effective in reducing rots during cold storage. There was a marked increase in the incidence of rots during shelf-life. These rots, primarily of the mold type—Penicillium digitatum Sacc. and P. italicum Wehmer, developed mostly in pits induced by the low storage temperatures.

With the expected ban on ethylene dibromide fumigation, cold exposure remains the only quarantine treatment for citrus fruit against the Mediterranean fruit fly. Following a cold treatment, ‘Marsh’ grapefruit (Citrus paradisi Macf.) developed chilling injury (Cl), mostly in the form of slight peel pitting on 3% to 10% of the fruit depending on the season and on other factors. There was no difference in the incidence of Cl between fruit treated at 0°C for 10 days or at 2.2° for 16 days as regulations require. The cold treatment also enhanced decay development during long-term storage of the fruit at 11°. Mold rots developed on Cl peel pitting, and their incidence increased from 1.7% to 3.5% during a storage period of 12 weeks. The presence of the fungicide Thiabendazole (TBZ) in the wax coating of the fruit reduced the incidence of Cl by more than 50%. Delayed cooling, i.e., keeping the freshly harvested packed fruit for 6 days at 17°C prior to initiation of cold treatment, reduced the incidence of Cl by the same extent. By combining a TBZ treatment with delayed cooling, the susceptibility of grapefruit to Cl can be reduced, and cold treatment can be practiced with a low risk of Cl and subsequent decay development.

In recent years the incidence of Fusarium spp. isolated from Stem End Rot (SER) and Internal Core Rot (ICR) of grapefruit and oranges has increased markedly. Fusarium spp. were isolated from apparently healthy green buttons and from the tissue underneath the button of healthy fruits. Of all the SER‐ and ICR‐rotted fruit, the incidence of Fusarium spp. alone and of Fusarium spp. with Alternaria citri was between 75 and 100%. Fusarium was also found to be the single causal agent of ICR of oranges and grapefruit. Species of Fusarium isolated from Stem End Rot and Internal Core Rot of citrus fruit were F. oxysporum, F. moniliforme and recently also F. culmorum.