आम के 9 प्रमुख रोग व उनका निदान कैसे करें
The mango (Mangifera indica) is an evergreen fruit tree. It is national fruit of India. It is a juicy stony fruit belonging to family anacardiaceae. The mango is native to South Asia. India accounting 42 % sharing in total world mango production. Mango is a rich source of vitamin C. dried mango skin and its seeds are also used in ayurvedic medicins. Mango leaves are used to decorate archways and doors in Indian houses. Mango also used for achar making, amchoor and for vegetable. Mango suffers from several diseases at all stages of its life. The major diseases of economic importance in India are:
1. Powdery Mildew (Oidium mangiferae)
The symptoms can be noticed on the inflorescence, stalk of inflorescence, leaves and young fruits. The characteristics symptoms of disease are white superficial powdery growth of the fungus on these parts. The effective flowers may fall prematurely and young fruits may remain on the tree until they reach up the marble size and then drop prematurely. Dropping of unfertilized infected flowers and young fruits leads to serious crop loss (20-80%).
- Pruning of diseased leaves and malformed panicles reduces primary inoculums.
- Three sprays of systemic fungicides during flowering season are recommended at 12-15 days intervals. 1st spray is recommended when there is 25% flowers opening.
2. Anthracnose/ Blossom Blight (Colletotrichum gloeosporioides)
Anthracnose manifests on different parts of mango tree. On the inflorescence, the earliest symptoms of the disease are the production of blackish brown specks on peduncles and flowers. Small black spots appear on the panicles and open flowers, which gradually enlarge and cause death of flowers. The infected flowers fall off, leaving the more persistence spikes on the peduncles, this leads to serious crop loss (10-90%). In leafy anthracnose Characteristics symptoms appear as oval or irregular brown to deep brown spot of various sizes scattered all over the leaf surface. Under damp conditions, the fungus grows rapidly. Young leaves are more prone to attract than the older ones. Insect attack may facilitate the entry of pathogen resulting into heavy incidence of disease.
- Diseased leaves, flowers, twigs and fruits lying on the floor of the orchard should be collected and all infected twigs from the tree should be pruned and burnt.
- Blossom infection can be controlled effectively by two to three sprays of contact or systemic fungicides during spring season at 12-15 days interval.
3. Mango malformation (Fusarium mangiferae)
Malformation is a serious threat to the mango growing areas of Pakistan as it causes crop loss upto 70%. Recent findings have demonstrated that the disease may be of fungal origin. Two distinct types of symptoms described by the workers are vegetative malformation (MV) and floral malformation (MF). Vegetative malformation is more pronounced in young seedlings as well as seedling trees than in the grafted plants. The affected seedlings developed excessive vegetative branches, which are of limited growth, swollen and have very short internodes. Malformation of inflorescence (MF) is a disease of inflorescence. The most characteristic symptoms of (MF) are the reduction and compact of internodes giving malformation a broom like appearance.
At present, no definite control measures for mango malformation can be advocated. However the following may reduce the incidence of malformation
- It is advisable to avoid scion stick from trees bearing malformed inflorescence for propagation.
- Only certified saplings should be used for propagation.
iii. As soon as the disease symptoms are well expressed, the affected terminals should be pruned along with the contiguous 15-20cm apparently healthy portion and burnt.
4. Alternaria leaf spot (Alternaria alternata)
Symptoms first appear as small, brownish circular spots on the surface of leaves. Later on, high concentration of brown black spots occurs evenly over the leaf lamina. Symptoms are more prominent on the lower side of the leaves. The tender leaves are found to be more susceptible than mature ones.
- The disease can be controlled by regular field spray program including copper based fungicides.
5. Bacterial Canker (Xanthomonas mangiferae)
On leaves, minute water soaked irregular to angular raised lesions is usually crowded at the apex. On young leaves halos are larger and distinct, while on older leaves, they are narrow could be observed only against light. Under severe infections, the leaf turns yellow and drop off.
- Regular inspection of orchards, sanitation and seedling certification are recommended as preventive measures against the disease.
- Spray of copper based fungicides has been found effective in controlling bacterial canker.
6. Stem End Rot (Lasiodiplodia theobromae, Phomospsis mangiferae, Dothiorella doninicana)
The fruit while ripening suddenly becomes brown to black typically at stem end. Within two three days whole fruit becomes a black and disease progress downwards, thus involving half of the area of the fruits. Though the flush of the whole fruit often wrinkles are also observed. Affected skin remains firm but decay sets into the pulp below and emits unpleasant odour.
- Prompt and proper handling of the fruit can minimize disease incidence.
- Fruit should be harvested with 10mm stalk.
- Pre-harvest sprays of any systemic fungicides or copper based fungicides reduce the incidence of SER.
- Post harvest dip of fruit in hot water supplemented with carbendazim or thiophanate methyl (0.05%) for 15 minutes at 52±1oC control the disease.
7. Die back (Lasiodiplodia theobromae, Natrassia mangiferae)
The disease is noticeable throughout the year but it is most conspicuous during October and November. It is characterized by drying up of twigs from top to downward particularly in the older trees followed by drying up of leaves which gives an appearance of fire scorch. The upper leaves lose their color and gradually dry. Drying of the whole leaf is accompanied by upward rolling of the margin. Such leaves shrivel, fall off within a month leaving the shriveled twigs all together bare, which is the characteristic symptom in the advance stage of the disease.
- Pruning of affected twigs (3’’ below the infection site) followed by spraying of copper based fungicides is the most effective method for the control of disease.
- In severe cases, the soil amendment with the removal of soil up to 9 inches deep under the canopy of the diseased tree and refilling with the canal silt, recommended doses of chemical fertilizers and FYM with pruning of affected twigs followed by three consecutive sprays of copper based fungicides at 15 days interval is also recommended.
8. Gummosis (Lasiodiplodia theobromae)
About 30-40% of young mango trees are affected by the gummosis especially when the mango tree is planted in sandy soil but its prevalence has also been noticed in other mango growing soils. The diseases is characterized by the presence of profuse oozing of gum on the surface of affected wood, bark of the trunk and also on larger branches but more common on the crack branches. In severe cases, droplets of gum trickle down on stem and bark turns dark brown with longitudinal cracks.
- The disease can be controlled with the regular sprays of copper based fungicides.
- The diseased bark / portion should be removed, cleaned and covered with copper based fungicides paste.
- Application of copper sulphate 500g in the sandy soil around the tree trunk is also advocated.
9 Root rot (Rhizoctonia )
Infection occurs at/or below the ground level the circular to irregular water socked patches. These patches enlarge and ultimately girdle the entire base of the stem. On account of rotting, the diseased tissues become soft, dark brown or black.
- Soil treatment with Thiophanate methyl, carbendazim or copper oxychloride @ 2g/ft2 is recommended.
- During the growing period any copper based fungicide should be sprayed on the plants.
Jitendra Sharma, Dr. G.S. Rathore, Richhapal Kumawat and Rajendra Jangid
Sri Karan Narendra Agriculture University, Jobner-303329