Study on the Causes of Resinous Latex Burnt on the Fruit Peel of 'Irwin' Mango
Chang, C. H.
A new disorder known as resinous latex burnt from lenticels of mango fruits in some orchards has been reported in Taiwan lately. The symptom caused the damage on fruit peel, and made those fruits not accepted by exporter. This experiment is attempted to explore the reason caused the resinous latex burnt on the fruit peel of Irwin mango. The surface temperature of mango fruits for and compared those are non-bagging, bagging in the open field and growing in greenhouse, were measured. It showed that the temperature both on the surfaces of fruit sunny face and shading face were no difference at night. But the day temperature for those fruits grow in greenhouse are the highest, up to 36ºC or 5ºC higher than those fruits growing in open field. Meanwhile, the resinous latex burnt rate was up to 100% on the fruits grown in the greenhouse. Those fruits sprayed with KH2PO4 0.1% before bagging caused a rate of 90% in resinous latex burnt the most serious rate of resinous latex sap and staining rate on the fruit peel when they were compare of to all the treatments, but it did not increase the fruit size, T.S.S. and improve the fruits peel color. Observed by microscope, the lenticels of Irwin mango fruit appeared at 56 days after blooming and the size up to 16 μm. Sap burnt from lenticels may begin at 77 days after blooming. But the fruits sprayed with KH2PO4 0.1% induced lenticels to appear earlier. Those lenticels size up to 250 μm and bigger than those fruits of the controls. We concluded that the temperature varied much from day to night at late development stage, or supplementary nutrient applications on the Irwin mango fruit both may seriously induce the resinous latex burnt on the fruit peel after early bagging-stage.
What is already known on this subject?
Supplementary nutrient applications by foliar sprays did not effectively increase fruit size, T.S.S. and peel color, but did increase the lenticels size. It makes the lenticels ease to burst up while the fruit grows up, and then cause the resinous latex burnt and stain on Irwin mango fruit peel.
What are the new findings?
This experiment is attempted to investigate the reason caused the resinous latex burnt on the fruit peel of Irwin mango. The result can be useful for farmers to regulate their cultivation practice to avoid resinous latex burnt.
What is the expected impact on this field?
By regulating the blooming stage or reducing the spray of what so called supplementary nutrient applications, the risks for damage on appearance of mango fruit could actually be reduced. Meanwhile, the labor and material used in cultivation also could be saved quite a lot by this way.
Key words: Mango, Lenticels, Latex, Physiological
Accepted for publication: August 31, 2016