Nutritional Deficiencies/Disorders of Coconut

Nitrogen

Nitrogen deficiency is typically caused by insufficient nitrogen in the soil. Nitrogen deficiency begins as a uniform light green discoloration / yellowing (uniform chlorosis) of the oldest leaves. Yellowing starts from tip to base of the lower leaves and will proceed up. As the deficiency progresses, younger leaves will also become discoloured. Older leaves are golden yellow colour. Growth virtually stops when N deficiency is severe and become shedding of leaves.

Correction measure: Foliar application of 2% urea thrice at fortnightly interval or soil application of 1-2 Kg urea / tree or root feeding of 1% urea 200 ml twice a year.

Phosphorus

Deficiency occurs in acid and alkaline soils. Purple coloration in leaves (in severe cases may leaves turn yellow before drying prematurely). Sluggish growth. Leaves stay upright. Premature leaf shedding. The growth, leaf size and leaf number reduced. The root growth is restricted if phosphorus deficiency is recorded.

Correction measure: Foliar spray of DAP 2% twice at fortnightly interval or soil application of FYM 5 Kg/tree. Root feeding of 1% DAP 2 ml twice a year.

Boron

Boron deficiency is caused by insufficient boron in the soil. It may be caused by soil drying and high soil pH, while temporary boron deficiency is caused by heavy leaching. Symptoms always occur on newly emerging leaves, and remain visible on these leaves as they mature and are replaced by younger leaves. One of the earliest symptoms of boron deficiency on coconut palm is leaf wrinkling and manifested as sharply bent leaflet tips, commonly called “hook leaf”. These sharp leaflet hooks are quite rigid and cannot be traightened out without tearing the leaflets. Leaves have a serrated zigzag appearance. One of the most common symptoms of boron deficiency is the failure of newly emerging spear leaves to open normally. In a chronic stage, multiple unopened spear leaves may be visible at the apex of the canopy. Boron deficiency also occurs in inflorescence and nuts. The inflorescence and nuts are become necrotic.

Correction measure: Application of borax/sodium tetraborate 0.2% (2 g/l of water), (75-100 ml/seedling), borax/ sodium tetraborate/octaborate 15-20 g/plan.

Manganese

The newest leaves of manganese deficient palms emerge chlorotic with longitudinal necrotic streaks. As the deficiency progresses, newly emerging leaflets appear necrotic and withered on all but basal portions of the leaflets. This withering results in a curling of the leaflets about the rachis giving the leaf a frizzled

appearance (‘frizzle top’). On new leaves of manganese-deficient palm, necrotic leaflet tips fall off and the leaf has a signed appearance. In severely manganese deficient palms, growth stops and newly emerging leaves consist solely of necrotic petiole stubs.

Correction measure: Soil application of MnSO₄ @ 10 Kg/acre

Magnesium

Magnesium deficiency appears on the oldest leaves of palms as broad chlorotic (yellow) bands along the margins with the central portion of the leaves remaining distinctly green. In severe cases leaflet tips may become necrotic. Older leaves become bronzed and dry appearance. Leaflets show necrosis and turn to reddish brown with translucent spots yellowing starts at the tip and spreads to the base.

Correction measure: Soil application of MgSO₄ 1-2 Kg/tree/year. Root feeding of 200 ml of 0.2% MgSO₄ twice a year

Sulphur

Typical symptoms are yellowish-green or yellowish-orange leaflets. Older leaves are remaining green. Leaves droop as the stem becomes weak. In older palms, leaf number and size are reduced. Sometimes an apron of dead fronds develops around the stem due to weakness of the rachis. Nuts may fall prematurely. Copra is rubbery and of poor market quality.

Correction measure: Soil application of gypsum 2 - 5 kg/tree/year. Root feeding of 0.2% gypsum

Iron

Iron deficiency usually appears on palms growing in poorly aerated soils or those that have been planted too deeply. Water logged soils and deep planting effectively suffocate the roots and reduce their effectiveness in taking up nutrients such as iron. The main symptom of iron deficiency is chlorosis or yellowing between the veins of new leaves (uniform chlorotic new leaves as the deficiency progresses, the tips become necrotic and leaf size reduced).

Correction measure: Application of FeSO₄ 0.25 to 0.5 Kg/tree/year

Zinc

Zinc deficiency is characterized by formation of small leaves wherein the leaf size is reduced to 50%. Leaflets become chlorotic, narrow and reduced in length. In acute deficiency, flowering is delayed. Zinc deficiency will also lead to button shedding. Its occurs mostly in saline soils.

Correction measure: Soil application of ZnSO₄ @ 10 Kg/acre

Calcium

Young leaves exhibit narrow white bands at margins. Interveinal chlorosis. Rusty appearance in leaf margin. Rolling up of leaves. Occurs only in acid soil.

Correction measure: Soil application of lime based on lime requirement and root feeding of 1% calcium nitrate.

Copper

Coppery bluish leaf. Rolling of terminal leaves due to loss of turgor. Leaves appear to be bleached grey. Fail to produce flowers.

Correction measure: Soil application of CuSO₄ @ 10 Kg/acre.

IPM for Coconut

To know the IPM practices for Coconut, click here.

Source: NIPHM and Directorate of Plant Protection, Quarantine & Storage