[ Abhimanyu Chaturvedi & Narendra Kumar ]
Orange is an economically important fruit crop in Arunachal Pradesh for its highly nutritive and commercial value. The Siang belt, besides Lohit and East Kameng districts are prominent, while Namsai, Changlang, Tirap, etc, are average production belts.
Premature fruit drop is a severe problem everywhere. Some fruits’ dropping at a certain stage of development is normal, but an excessive drop of older fruits could indicate a number of problems.
In cause of normal fruit drop, orange trees normally drop some of their young fruits as a means to thin the fruit out and devote resources to the development of the fruits that remain. Beginning soon after blossom drop, and ending when the fruit has a diameter of about 1/2 inch, it is normal if approximately 80 to 90 percent of the fruits falls off the tree.
A small number of fruits may continue to drop as they grow.
A number of nutrient deficiencies can contribute to excessive fruit drop, and identifying the exact nutrient deficiency means that you can apply the right fertiliser to correct the deficiency. A nitrogen deficiency appears first as a yellowing of older leaves, while a magnesium deficiency appears as a yellowing between veins on older leaves and leaf drop. Inadequate zinc causes young leaves to be abnormally small and have yellow blotches between veins, particularly on the south-facing side of the canopy. A citrus tree lacking manganese has leaves that turn a lighter green between leaf veins.
In heavy fruiting years, low potassium levels can impact fruit drop. Good water management is crucial to avoid excessive fruit drop and other citrus tree problems. Excessive watering, poorly drained soils, or drought stress can lead to fruit drop. As a general rule, citrus trees prefer slow, deep watering every five to 14 days during dry, hot weather, depending on the citrus tree’s age, and every 14 to 30 days during cool, wet weather, or whenever the soil 6 inches below the surface near the tree feels dry to the touch.
Sudden changes in temperature, particularly when high temperatures occur at or shortly after fruit set, can cause fruit drop.
The following points should be followed by orange growers:
- Smearing of orange trunk up to one metre from the ground level with a mixture of monocrotophos insecticide + agricultural lime + water (1 litre + 10 kg + 100 litre). This is a very important operation to check the attack of stem/trunk borers which cause heavy damage to the crop. This is the right time for smearing because the female insect of borer lays eggs around the stem of orange (during current period of time) and maggots cause damage.
- Application of agricultural lime @ 2 kg/plant (for > 3 years old orange plants) is necessary because lime balances the soil reaction, which favours availability of nutrients in sufficient amounts from soil. The lime can be mixed with farmyard manures (5 kg/plant) and should be apply around the trunk in basin form.
- Spraying of 0.2 percent solution of micronutrient mixture is beneficial to prevent fruit drop as well as better growth and development of fruits. (The writers are members of Deomali-based Krishi Vigyan Kendra, Tirap.)
