Nitrogen, Phosphorus, Potassium Impotrance

Plants make most of their food by photosynthesis. But  they also need mineralsto be healthy. Plants cannot make minerals. They get them from the soil. Some of the minerals they need include the following:

Nitrates

Nitrates provide nitrogen. Nitrogen helps plants grow. All living cells contain nitrogen. Nitrogen is also part of chlorophyll, the pigmentthat traps sunlight. No nitrogen means no photosynthesis. You can tell if a plant does not have enough nitrogen. It will be small. Its older leaves will be yellow.

 Phosphorus

Phosphorus is important for photosynthesis, respiration, and growth. It encourages roots to grow well. You can tell if a plant does not have enough phosphorus. Its roots will be stunted. Its younger leaves will be purple.

Potassium

Potassium helps chemicals called enzymes to work. Enzymes are needed in photosynthesis and respiration. Potassium can also protect a plant from disease. You can tell if a plant does not have enough potassium. Its leaves will be yellow. They will have dead parts on them.

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Mango Diseases and Management

Mango

Diseases

Powdery Mildew (Oidium mangiferae)

Powdery mildew is one of the most serious diseases of mango affecting almost all the varieties. The  characteristic symptom of the disease is the white superficial powdery fungal growth on leaves, stalk of  panicles, flowers and young fruits. The affected flowers and fruits drop pre-maturely reducing the crop load considerably or might even prevent the fruit set. Rains or mists accompanied by cooler nights during flowering are congenial for the disease spread.

Control : Alternate spraying of Wettable sulphur 0.2 per cent (2 g Sulfex/litre), Tridemorph O.1 per cent  (1 ml Calixin/litre) and Bavistin @ 0.1 % at 15 days interval are recommended for effective control of  the disease. The first spray is to be given at panicle emergence stage.

Anthracnose (Colletotrichum gloeosporioides) :

It is of widespread occurrence in the field and in storage. The disease causes  serious losses to young shoots, flowers and fruits under favorable climatic  conditions (high humidity, frequent rains and the temperature range of 24-32°C). The disease produces leaf spot, blossom blight, withered tip, twig blight and fruit rot symptoms. Tender shoots and foliage are easily affected which ultimately cause die back of young branches. Older twigs may also be infected through wounds, which in severe cases may be fatal. Black spots develop on panicles. Severe infection destroys the entire inflorescence resulting in failure  of fruit setting. Young infected fruits develop black spots, shrivel and drop off.  Fruits infected at mature stage carry the fungus into storage and cause considerable loss during storage, transit and marketing.

Control : The diseased twigs should be pruned and burnt along with fallen leaves. Spraying twice with  Carbendazirn (Bavistin 0.1%) at 15 days interval during flowering controls blossom infection. Spraying  of copper fungicides (0.3%) is recommended for the control of foliar infection. Postharvest disease of mango caused by anthracnose could be controlled by dip treatment of fruits in Carbendazim (0.1%) in hot water at 52 C for 15 minutes.

Die Back (Botryodiplodia (Lasiodiplodia) theobromae) :

Die back is one of the serious diseases of mango. The disease on the tree may be noticed at any time of the year but it is most conspicuous during October-November. The disease is characterized by  drying of twigs and branches followed by complete defoliation, which gives the tree an appearance of  scorching by fire. Initially it is evident by discoloration and darkening of the bark. The dark area  advances and extends outward along the veins of leaves. The affected leaf turns brown and its  margins roll upwards. At this stage, the twig or branch dies, shrivels and leaf falls. This may be  accompanied by exudation of yellowish brown gum.

Control : Pruning of the diseased twigs 2-3 inches below the affected portion and spraying Copper  Oxychloride (0.3%) on infected trees controls the disease. The cut ends of the pruned twigs are pasted  with Copper Oxychloride (0.3%).

Phoma Blight (Phoma glomerata) :

The symptoms of the disease are observed only on old leaves. Initially, the lesions are angular, minute,  irregular, yellow to light brown, scattered over leaf lamina. As the lesions enlarge, their colour changes  from brown to cinnamon and they become almost irregular. In case of severe infection such spots  coalesce forming patches resulting in complete withering and defoliation of infected leaves.

Control : The disease is controlled by spraying Benomyl (0.2%) just after the appearance of the  disease followed by 0.3% Miltox (Copper Oxychloride + Zineb) at 20 day interval.

Bacterial Canker (Xanthomonas campestrispv. mangiferaeindicae) :

Canker is a serious disease in India. The disease causes fruit drop (10-70%), yield loss (10-85%) and  storage rot (5-100%). Many commercial cultivars of mango including Langra, Dashehari, Arnrapali,  Mallika and Totapuri are susceptible to this disease. The disease is found on leaves, petioles, twigs,  branches and fruits. The disease first appears as minute water soaked irregular lesions on any part of  leaf or leaf lamina. Several lesions coalesce to form irregular necrotic cankerous patches. In severe  infections the leaves turn yellow and drop off. Cankerous lesions also appear on petioles, twigs and  young fruits. The water soaked lesions also develop on fruits which later turn dark brown to black. They  often burst open, releasing highly contagious gummy ooze containing bacterial cells.

Control :Three sprays of Streptocycline (0.01%) or Agrimycin-100 (0.01%) after first visual symptom  at 10 day intervals and monthly sprays of Carbendazim (Bavistin 0.1%) or Copper Oxychloride (0.3%)  are effective in controlling the disease.

Red Rust (Cepbaleuros virescens) :

The disease attack causes reduction in photosynthetic activity and defoliation of leaves thereby  reducing the vitality of the host plant. The disease is evident by the rusty red spots mainly on leaves and  sometimes on petioles and bark of young twigs. . The spots are greenish grey in colour and velvety in  texture. Later, they turn reddish brown. The circular and slightly elevated spots sometimes coalesce to  form larger and irregular spots. The affected portion of stem cracks. In case of severe infection, the  bark becomes thick, twigs get enlarged but remain stunted and the foliage finally dries up.

Control : Two to three sprays of Copper Oxychloride (0.3%) is effective in controlling the disease.

Sooty Mould (Meliola mangiferae) :

The disease is common in the orchards where mealy bug, scale insects and hoppers are not controlled  efficiently. The disease in the field is recognized by the presence of a black sooty mould on the leaf  surface. In severe cases, the trees turn completely black due to the presence of mould over the entire  surface of twigs and leaves. The severity of infection depends on the honey dew secretion of the above  insects. Honey dews secretions from insects stick to the leaf surface and provide necessary medium  for fungal growth. Although the fungus causes no direct damage, the photosynthetic activity of the leaf  is adversely affected.

Control :Pruning of affected branches and their prompt destruction followed by spraying of Wettasulf  (0.2% )+ Metacid (0.1 %)+ gum acacia (0.3%) helps to control the disease.

Diplodia Stem-end Rot(Lasiodiplodia theobromae) :

The fungus enters through mechanically injured areas on the stem or  skin. The fungus grows from the pedicel into a circular black lesion  around the pedicel.

Control : Careful handling to minimize mechanical injuries. Postharvest dip of fruits in Carbendazirn (0.1%) in hot water at 52 ± 1°C for 15 minutes controls the disease in storage and transit.

 

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