Control Methods for Three Major Physiological Diseases in Navel Orange Cultivation

For fruit cracking disease, the first step is to select varieties (lines) with strong cracking resistance. Generally, varieties (lines) with oval fruit shape, small navel or closed navel have better cracking resistance, such as Newhall and others; second, scientific management should be strengthened to enhance tree vigor. Especially during the dry period after the plum rain season and before the autumn rains arrive, water management must be done particularly well, with timely irrigation or watering (spraying) to keep the soil moist and promote normal fruit growth and development. Third, during the rapid fruit expansion period, spray foliar potassium fertilizer 2 to 3 times consecutively.

For sunburn disease, covering the orchard with straw and other materials to preserve soil moisture is the foundation for preventing sunburn disease; planting forage grass or interplanting green manure in the orchard can reduce sunburn disease; during high-temperature seasons, do not spray pesticides such as machine oil emulsion and lime sulfur mixture, so as not to aggravate the occurrence of sunburn disease. In the early stage of sunburn disease, paste white paper onto the surface of sunburned fruit, and pull branches and leaves to shade the fruit, so as to reduce direct sunlight exposure.

For navel yellow disease, first start with cultivating vigorous tree vigor, appropriately increase nitrogen fertilizer application, and improve the tree's nutritional level and nitrogen metabolism function; second, before flowering, pull strong autumn shoots into a drooping or horizontal state, so that most flowers face downward when opening, reducing sun-facing fruit and preventing the occurrence of navel yellow; from late July to late August, apply 600-times “Yi Huang Zhi” solution to coat and spray the navel part of the fruit, in order to suppress the occurrence and spread of navel yellow disease.