This is mainly a physiological disorder and is largely attributed to high atmospheric humidity following heavy rains or heavy irrigation during hot weather. Two types of splitting, namely radial and transverse have been noticed. Radial cracking is more common than transverse one. Partial splitting is more prevalent while splitting down to inner core is rather rare. Often the cracked surface of the fruit gets infected by disease causing organisms such as Aspergillus, Aalternaria, Fusarium, and Penicillum which lead to partial rotting and early fruit dropping from trees.
Control: The disease can be minimized by frequent and light irritations during the dry and hot periods and early picking of fruits soon after maturity.
The causes attributed to fruit drop in citrus are lack of fertilization, mechanical shock, insects,disease, high temperature, rainfall, and defective irrational practices. The most pronounced stages of fruit drop occurs when the fruits are at marble stage. It lasts for a month after full bloom.On the onset of hot summer weather during May-June the second wave of intense fruit drop occurs while pre-harvest drop occurs during ripening period, which lasts from August-January.
Control : The method of control depends upon the causes of the drop and the variety of the fruit. In order to reduce the pre-harvest drop, NAA (10 ppm) is sprayed from August till October at monthly interval.
Citrus die back or orchard decline is a gradual deterioration process exhibiting loss of vigor, death of twigs and branches, reduction in yield and ultimate death.Many factors such as unsuitable soils, drought, lack of systematic manuring, general neglect, use of infected bud wood and field incidence of vector-bore virus disease contribute to this declining condition singly or in combination. There is no external remedy to check viruses. It is, therefore, absolutely essential to manage the citrus orchards with utmost care.
Control: Adopting a package of practices such as selection of proper site and soil, raising of genuine and healthy plants from certified bud wood, use of proper root stock, judicious irrigation and manuring and scientific spray schedule against insect pests and diseases can successfully control the disease.
It is caused by rind oil release when oil cells get ruptured during harvesting or during handling from the field to the pack house. It is more common in crop taken in 'Mrig' bahar and harvested during February March. Careful harvesting and handling reduces incidence of oleocellosis. Rind oil from ruptured cells discolors the skin making the fruit unmarketable.
Control: Best way to reduce its incidence is to cure the fruit overnight at a temperature of 18-20 C for 12-24 hrs, before the fruit is moved from the field to the pack house.