ALTERNATIVE TREATMENTS TO CONTROL POSTHARVEST DECAY IN LATE SEASON TANGERINES

The occurrence of postharvest decay in tangerines in southern Brazil is mostly due to high inoculum pressure in orchards. Measures used to reduce the after-harvest percentage of rotted fruit include both preharvest and customary postharvest treatments. Alternative methods to control postharvest diseases are needed to address consumer demands for safe food, especially with regards to pesticide residues. At the postharvest lab of the Faculdade de Agronomia – UFRGS, several trials were conducted with two late season tangerine cultivars (‘Montenegrina’ and ‘Hada’) in which sodium bicarbonate (2%, v/v), an antagonist (Bacillus subtilis), heat treatments, chloride dioxide, or tea tree oil (Melaleuca alternifolia) in combination with and without carnauba wax were tested against a control fungicidal treatment ofimazalil (2 ml L^-1). After up to 60 days of storage at 5°C, the tangerines were analyzed for decay incidence and quality parameters. No negative impact was observed on soluble solids and titratable acidity, as well as epidermal color, after retrieval from cold storage plus 3-5 more days at room temperature. On ‘Hada’ tangerines, the tested alternatives to the fungicide treatment resulted in adequate control of decay, which remained below 5%. On ‘Montenegrina’ fruit, however, decay control using either single or combined treatments were not very effective, except for imazalil, in the reduction of Penicillium spp. incidence after 60 days of cold storage. Waxing had no effect on the impact of the treatments.