Learn about the pests that damage ber and its control.
1. Ber Fruit Fly, Carpomyia Vesuviana Costa (Diptera: Tephritidae):
This pest is widely distributed in India, Pakistan and southern Italy. It is most destructive to ber fruits of the species Ziziphus mauritiana Lam. and Z. jujuba Mill, in India and Z. sativa China in Italy. Also, C. vesuviana, Bactrocera dorsalis (Hendel) and B. correcta (Bezzi) have been recorded as minor pests of ber fruits.
Damage is caused only by the larvae which are creamy white and slightly smaller than those of other fruit-flies. The adults, smaller than the housefly, are brownish yellow, with brown longitudinal stripes on the thorax, being surrounded on the sides and the back with black spots. There are greyish brown spots on the wings and bristly hair on the tip of the abdomen.
Life-Cycle:
The pest is active during winter and hibernates in the soil from April to August in the pupal stage. The flies emerge from the pupae during August to mid-November, synchronizing with the blossoming and fruit setting of the ber trees. Flies that emerge early in the season are small and generally die without reproducing.
The flies are very fast fliers but the females can easily be caught when ovipositing on very young fruits. At the age of one month, the flies make cavities in the skin of fruit and lay one or two spindle-shaped creamy-white eggs, 1 mm below the skin; leaving behind a resinous material.
There is no further growth of the fruit in the vicinity of this puncture and, hence, the fruits become deformed. The eggs hatch in 2-3 days and the maggots feed on the flesh of the fruit, making galleries towards the centre. Such fruits invariably rot near the stones, and as many as 18 maggots have been recorded from one attacked fruit.
The larvae are full-grown in 7-10 days and they come out of the fruit by cutting one or two holes in the skin. They move away, making jumps of 15-26 cm and reach a suitable place to pupate generally 6-15 cm below the soil surface. The pupal stage lasts 14-30 days and the shortest life-cycle, from egg to the emergence of the adult, is completed in 24 days. There are 2-3 broods in a year.
The pest becomes active in the autumn and builds up population in the winter, reaching a peak in February-March. At that time, all the late-maturing ber fruits are found riddled with maggots.
Damage:
Fleshy varieties of ber are more seriously damaged than the less fleshy ones. The attacked fruits are rotten near the stones and emit a strong smell. Late maturing fruits are destroyed almost entirely.
Control:
(i) Collect and destroy the fallen infested fruits at alternate days.
(ii) Rake the soil around the trees during summer to expose the pupae to heat and natural enemies.
(iii) Do not allow wild bushes, trees, isolated growing or abandoned plants of other Ziziphus species to grow in the vicinity of ber orchards, as their fruits serve as good source for multiplication and help in carry over of fruit flies to cultivated ber fruits.
(iv) To escape egg laying on fruits, do not allow the fruits to ripe on the trees, harvest at green and firm stage.
(v) Spray 1.25 litres of dimethoate 30EC in 750 litres of water per ha during February- March, and repeat sprays at 10 days interval. Stop spraying at least 15 days before fruit picking.
2. Lac Insect, Kerria Lacca (Kerr) (Hemiptera: Kerriidae):
The lac insect is found in India, Pakistan, Sri Lanka, Myanmar, Malaysia, China and Thailand. The insect is used for commercial production of lac in Bihar, Madhya Pradesh, West Bengal, Maharashtra, Uttar Pradesh, Orissa and Assam. However, it is considered as a pest when it feeds on plants of economical significance.
The pestilent aspect of this insect has largely been overshadowed by its usefulness. The major host plants of lac insect are ber, kusum (Schleichera oleosa), palas (Butea monosperma) and khair (Acacia catechu). It also attacks grapevine, pomegranate, amla or Indian gooseberry (Emblica officinalis), litchi, sugar apple, tamarind and several forest and avenue trees.
The newly hatched nymph (crawler) is 0.60 × 0.25 mm in size and pinkish in colour. The female is apterous, pinkish in colour and about 1-5 mm in length. The ventral surface of the body is flat while dorsal surface is convex. The males are pinkish-red in colour and are of two types- winged and wingless. Winged male possesses only one pair of translucent membranous forewings.
Life-Cycle:
A female lays about 200-500 eggs underneath its body in lac encrustation. The eggs generally hatch within a few hours as the embryos are fully developed in them. Thus the lac insect has ovoviviparous mode of reproduction. The first instar nymphs (crawlers) emerge in large numbers and come out of lac encrustations.
The emergence of nymphs, called swarming, may continue for 5 weeks or more. The nymphs crawl about on the branches for some time and on reaching soft succulent twigs, settle down gregariously and thrust their needle-like proboscis into the bark and start sucking the sap.
Once settled, the nymphs do not move. After one or two days of settling, they start secreting resin from glands distributed under the cuticle all over the body, except near the mouth parts, two breathing pores and anus. The resinous covering increases in size with the growth of the insect.
As the nymphs settle very close together, the lac secretion from adjacent cells coalesces to form a continuous encrustation. Males produce smaller quantity of lac in comparison to females which produce the commercial lac. The nymphs molt thrice before reaching the adult stage. The peak periods of activity of the lac insect are January-February and June-July.
The two most important predators of the lac insect are the large white lac moth, Eublemma amabilis Moore (Noctuidae) and the smaller black lac moth, Holcocera pulverea Meyr (Gelechiidae).
Damage:
De-sapping by large population of lac insect over a long period of time reduces the vitality and vigour of the trees resulting in substantial loss in fruit yield and quality. The cottony appearance of certain healthy encrustations is due to long wax filaments, while the sooty appearance on the leaves is due to black mould growth on the honeydew which imparts ugly appearance to the trees.
The severely infested branches dry up. Neglected ber orchards having close plantations, intermixed with other host trees and devoid of regular summer pruning are more prone to lac infestation. Old branches harbouring lac encrustations of the previous generation serve as source of infestation for the next brood.
Control:
(i) After fruit harvest or when trees are in dormancy, prune all severely infested branches and burn without delay.
(ii) Avoid overcrowding and growing other lac insect host plants in the vicinity of fruit trees.
(iii) Spray 625 ml of dimethoate 30EC in 625 litres of water per ha in April and again in September.
3. Ber Beetles, Adoretus Pallens Arrow and A. Nitidus Arrow (Coleoptera: Scarabaeidae):
These two defoliating beetles are widely distributed in northern India and Pakistan, and are polyphagous, but they prefer the ber tree (Zizyplius jujuba) and the grapevine. Only the adult beetles are destructive and can be recognized from their bright yellow colour and yellowish-brown shiny wings. Tarsi on the tips of their legs are deep red and their size varies from 9 to 13 mm. The beetles are attracted to light and appear in large numbers late in spring or early in summer and again during the monsoon.
Life-Cycle:
This pest is active during summer and passes the winter in larval stage. The adults appear in April-May and lay white, smooth, elongate eggs, singly in the soil near the host plants. Egg laying continues at irregular intervals from May to August and the eggs hatch in 6-9 days in that season. The whitish grubs feed on soil humus, roots of grasses and other vegetable matter found under or near the ber trees.
When full-grown, the grubs measure 15 mm in length and are creamy white. They make an earthen cell in the autumn and hibernate through the whole of winter. Pupation takes place sometimes during next April and the adults emerge after 11-12 days. There is only one generation in a year.
Damage:
Damage is characterized by round holes cut in the leaves by beetles during the night. The ber trees are sometimes so heavily attacked that the entire foliage may disappear and such trees do not bear any fruit. The attack starts early in the spring and continues up to August.
Control:
(i) Light traps are quite effective in trapping the adult beetles.
(ii) Raking around the trees in useful in exposing the hibernating grubs and killing them.
(iii) Spray 2.5 kg of carbaryl 50WP in 750 litres of water per ha in the evening as soon as the damage starts. If the damage continues, repeat the spraying after one week.