Quest for desirable quality of Tango Mandarin in the citrus greening era: The promise of integrated approaches

Abstract

Huanglongbing (HLB), a citrus disease, has caused >70% decline in Florida citrus production over the past decade. Fruit from HLB-affected trees are small, lopsided, uneven colored, with bitter and acidic taste, making them undesirable for the fresh market. ‘Tango’ mandarin is fairly tolerant to HLB, but achieving acceptable peel color under Florida conditions is challenging. Therefore, preharvest foliar-applied mineral nutrients (K + Ca, K + B, and Ca + B) applied to HLB-affected ‘Tango’ trees followed by postharvest degreening were evaluated for their effects on fruit quality and storage life. In addition, degreening followed by thiabendazole fungicide and storage conditions (4 ± 1 °C or 24 ± 1 °C) were evaluated. The K + B treatment resulted in fewer HLB-symptomatic fruit, as well as greater fruit weight and diameter, and better peel color development. Degreening fruit allowed marketable color to be achieved. Compression forces for both healthy and HLB-affected fruit, and peel puncture resistance forces for healthy fruit were higher in cold storage than ambient storage. Thiabendazole-treated fruit had less storage decay incidence than non-treated fruit at room temperature, and no decay was observed in cold storage. Overall, preharvest K + B spray and degreening, alone or in combination, are potent tools for achieving marketable peel color of ‘Tango’ fruit from HLB-affected trees.