Major problem in citri culture

a) Citrus decline/Dieback

Causes

• Soil factor
• Nutritional factor
• Orchard management
• Insect’s pests
• Nematodes
• Diseases

b) Granulation

• It is the physiological disorder of the juice sacs of citrus fruits where they become comparatively hard, assumes a grayish color and become some what enlarged.

Factors affecting granulation

• Climate: humid climate
• Species and cultivars: sweet orange
• Mineral nutrition: boron and zinc deficiency
• Enzymes and plant growth regulator: Higher level of auxins, cytokines and abscissic acid and low gibberellins
• Crop load: heavy load
• Three spray of 25 ppm Boric acid, 1% Potassium nitrate and 2% Calcium hydroxide at monthly intervals starting from 10 September reduced granulation.

c) Fruit drop:

• Post setting drop: a drop after fruit set.- due to over population and lack of pollination and fertilization.
• Summer or June drop- this occurs in late spring or early summer when the temperature is high and air and soil are dry.
• Pre harvest drop- drop of mature fruit due to auxins and gibberellins deficiency.

Physiological cause of fruit drop

• Lack of pollination and fertilization.
• Hormonal imbalance.
• A very hot or dry speel for a long period.
• Lack of adequate moisture in a soil.
• Insects pests like citrus bud mite, mealy bug, fruit flies and diseases

Control: Spray 10 ppm of 2,4-D in September about 2 months before harvesting.