Nursing sick plants back to health
By Satish Narula

PLANTS, like other living beings, conkey ‘feelings’ through symptoms. For those who understand their language, plants do talk. Sometime it is leaf eaten or rolled to say ‘a hiding insect’, a cupped leaf means the sapis sucking is while spots represent various fungi.

It is not always insects or disease that show symptoms. Nutritional deficiencies also appear prominently on leaves, twigs or even fruits. Depending upon the element that is deficient, symptoms may appear on young growth or old leaves. It is not always possible to specify the deficient element . But when you find little leaves, witch’s broom, yellow mottling, twig die back small or premature fruit falling-think of zinc.

A number of elements, play an important role in the plants’ health. Zinc, although required in minute quantities, is indispensible. Effects of its deficiency are noticed on mango, guava, litchi, stone fruits and on ornamental plants like ixora. But most of all zinc deficiency affects on citrus trees and is one of the factors responsible for their decline.

Zinc deficiency in citrus is easy to spot. It appears as irregular "interveinal chlorosis" commonly called "mottled leaf." The leaf turns yellow, prominently showing veins that remain green. The terminal leaves become small and narrow giving a "little leaf" effect. The fruit and bud formation is severely affected and there is twig die back.

In case of severe zinc deficiency, the leaf may turn entirely yellow but usually the irregular areas along the veins remain green giving a sharp colour contrast between the veins and the interveinal areas. The leaves become very small and pointed. Small leaves and chlorosis (yellowing) of leaves over a longer duration, results in the reduction in tree vigour and yield. The fruit produce on such trees is also of low quality.

Zinc deficiency is easy to control. In case of citrus trees, spray the affected trees with 0.3 per cent zinc sulphate without the addition of lime (chunna) in April-May. For this add three grams of zinc sulphate to a litre of water. The spray can be repeated on the summer flush in June and then on late summer flush in August-September. The foliar spray is done on the fully developed flushes. Zinc deficiency become acute after the first fruit-bearing in the fourth year.

A spray of the same concentration should be given in April too, right from the onset of the third year. In case you have to spray Bordeaux mixture, blitox etc. give a gap of at least a week between the spray of these chemicals and zinc. For acute zinc deficiency, 0.45 per cent solution without addition of lime could provide quick recovery. For this, dissolve four-and-a-half gm of zinc sulphate to a litre of water.

Zinc deficiency in guava is also identified by small leaves with chlorosis in between the veins. The deficiency of this can cause suppression of growth and a die back of branches. In this case zinc sulphate is to be sprayed with unslaked lime. For this, mix 100 gm of zinc sulphate and 30 gm of unslaked lime in one litre of water. Use this spray two or three times at fortnightly intervals.

Zinc deficiency is also observed in plum, especially in light soils during summer months. It could be corrected by a foliar spray obtained by mixing 60 gm of zinc sulphate and 30 gm of unslaked lime in 10 litre of water.

No doubt farm yard manure and poultry manure contain zinc but its quantity is not sufficient. Moreover, it takes long to affect the plants.

This feature was published on June 6,1999