Fruits tree is prone to a variety of diseases that can harm the tree, reduces the yields or in certain case tree dies. Fortunately, orchardist can avoid most of the diseases by taking chemical and non-chemical measures. Here we have listed the most common fruit tree diseases.
Small sunken brown small holes develop on the surface of the fruit and the flesh beneath the pits is discolored and dry initially it is light brown slowly or with fruit maturity it turns into dark coloured. In severe cases, brown dots area of tissue are scattered throughout the fruit flesh of an infected apple and it takes on an unpleasant, bitter taste or sponge like taste. This can appear from when the fruits are about half developed until they are harvested.
It is more common on young, vigorously-growing trees; especially those fed heavily with nitrogenous fertilizers; but it can also develop on fairly old trees.
Correct nutrients and irrigation to maintain steady growth throughout the fruit season is the key to reducing problem of dark spots / bitter pit. Use a general-purpose, balanced fertilizer and nitrogenous (such as sulphate of ammonia) or potassium-rich (such as sulphate of potash) fertilizers, excessive use of these should be avoided. Moisture through regular irrigation should be there. Summer pruning helps to rescue the leave area of apple trees which helps to control the strength of trees and redirects calcium to fruits instead of vegetation, as well as foliage.
Foliar sprays of calcium nitrate can be applied between May to June to give the required calcium to the fruit also avoid heavy pruning. Proper spraying intervals should be followed as per the chemicals/organics used and never mix with fungicides or insecticides this can react and can damage the fruits. Add a wetting agent or a few drops soap to help products adhere to leaves. Only spray when a temperature is below 21°C and only in the evening to avoid ‘russeting’ (where apple skins develop rough, brownish patches)
Foliar calcium sprays before harvest and dipping fruits in calcium before storage control the occurrence of bitter pit. The plants should be sprayed 60 days prior to harvest followed by a repeat spray after 30 days, for better result, read the manufacturing instructions.
Measures :Proper nutrient management, especially boron and calcium helps in preventing this disorder foliar spray of calcium and fertilizers can help to prevent it.
Circumstances range from a small spot of brown flesh to entire browning of flesh with a margin of healthy white flesh remaining just below the skin, it develop early in storage and may increase in severity with extended storage time.
Harvesting of over mature fruits should be avoided, if harvested should be properly stored. The fruits should be immediately harvested when it ripe. The CO concentrations should be reduced to avoid development of brown heart.
One of the suggested methods of control is to avoid sudden exposure of fruit to intense heat or direct sun light. Summer pruning must be carefully done to avoid sunburn. Heavily pruned orchards or orchards with less leaves should be regularly irrigated to reduce heat stress.
Russeting of apples in a humid environment is a major concern reason of the fruit growers. Russeting occurs shortly after petal fall and fruit is about to set. The apple cultivars, which have thin cuticle, are more susceptible to russeting. It is commonly noticed on exposed fruits than on fruits remaining in shade. Frost during the blossom or at the early fruit formation stage may also cause russeting. Russeting leads to rupture of the fruit skin and development of cracks and result in distorted shape of fruits
Selection of less susceptible clones and adequate irrigation, manuring, nutrient pest and effective management can reduce russeting.
The pre-harvest drop can be controlled by application with NAA (15 ppm) sprayed 20 days before the expected fruit drop or 20-25 days before the harvest.