Learn about the pests that damage temperate fruits and its control.
1. Peach Leafcurl Aphid, Brachycaudus Helichrysi (Kaltenbach) (Hemiptera: Aphididae):
This worldwide aphid is a very destructive pest of peach, plum, almond (Amygdalus communis L.) and other temperate fruits. It is prevalent both in the plains and in the mountainous areas of India, up to an altitude of 2,200 metres. In spring and early summer, the infested plants show curling of the new leaves. The development of fruits is very slow and due to lack of nutrition, they fall prematurely.
This damage is caused by nymphs and females which are confined to the growing shoots and leaves, from where they suck the cell-sap. This plant louse is very small and is generally yellow, with dark stripes on the head. Its colour varies according to the host plant. For example, on peach, it is light green and on golden-rod it is greenish yellow.
Life-Cycle:
This pest is active from February to March on temperate fruits and from June to October on golden-rod. During the winter, it is found only in the egg-stage at the base of the buds. With the flow of cell-sap during the spring, the eggs hatch and the nymphs move on to the primordial leaves where they start sucking the sap.
In about four weeks’ time, the nymphs are full- fed and change into non-winged adults. There are no males. The females produce eggs without fertilization and this hatch inside the body of the mother. Thus, the females give birth to young ones instead of laying eggs. Each viviparous– female produces about 50 young aphids in her short lifetime of about 13 days.
Three or four generations are completed on the fruit plants. With the warming up of the season, winged males and females are also produced. They migrate to other alternative host plants, such as golden-rod, and again start reproducing asexually. Four or five generations are completed on golden-rod from June to October.
Early in November, the winged females are produced again. They migrate back to peach, plum and other fruit-trees. The old foliage has been shed by that time, therefore, the females lay eggs at the base of the buds. Egg-laying is completed by the middle of December, when the females die.
In the plains, another species, Myzus persicae (Sulzer), has been recorded as a serious pest of peach trees.
Damage:
The nymphs and females suck the sap from young leaves and cause them to curl. The severely attacked plants have only small crumpled or twisted leaves and bear very little fruit. The curling of the peach leaves is also caused by the fungus, Taphrina deformans Berk & Tul, in which a curled leaf becomes thickened near the midrib and is brittle and lustrous.
Control:
(i) For effective management of aphid, removal of weeds which act as secondary hosts is essential,
(ii) Spray 2.0 litres of malathion 50EC or dimethoate 30EC in 1250 litres of water per ha. One pre-bloom and a post-bloom spray at 10-day interval should be given.
2. Cherry Stem Borer, Aeolesthes Holosericea Fabricius (Coleoptera: Cerambycidae):
This polyphagous defoliating beetle is widely distributed in India, Sri Lanka, Bangladesh, Myanmar, Malaysia and Thailand. The grubs of the beetle are the most destructive pests of cherry and they also attack apple, guava, apricot, crab apple, mulberry, peach, pear, plum, walnut and other trees.
The adults are dark brown, 38-45 mm long, having short mottled yellowish pubescence on the elytra. Antennae of the male are 1.5 times their body length, while those of the female are about the same length as the body. The flabby grubs are yellowish in colour and are clothed with fine bristles. They feed inside woody portion of the host trees and when full-grown, they measure 70- 80 mm long.
Life-Cycle:
The beetles emerge out of the tunnels in the host trees from May to October and are active throughout the summer. After mating, the females start laying eggs on the dry woody portions of the host trees in the cuts or in cracks and crevices of the bark. A female, on an average, lays about 100 eggs. The eggs are white, elliptical in shape and are about 2.5 mm in length.
They hatch in 7-12 days and the young grubs on emergence feed first on the bark and, as they grow in size, they bore deeper inside the woody portions of a tree branch. In summer, they feed at a fast rate, throwing frass from the exit holes. As a result of their feeding and cutting into the wood, sap flow in that portion of the branch or the trunk becomes restricted. It gradually causes death of that portion.
In the winter time, the rate of feeding of the grubs is very slow and it is seen quite often that the full-fed grubs may just rest in the tunnels without feeding.
The larval period is completed in 27-32 months. The pre-pupal period varies from 3 to 150 days and pupation takes place either in October-November or in March-April. The pupal stage lasts from 40 to 100 days. The beetles that emerge from puparia formed in October remain within the tunnels throughout the winter and the spring, while those beetles that emerge from the puparia formed in April, rest for only 6 weeks. Thus, the life-cycle is completed in three years.
Damage:
The newly hatched grubs first feed on bark and make zig-zag galleries. They bore inside and feed on sap wood. As a result of their feeding and the consequential damage to the woody tissue, the vitality of the trees is reduced. Parts of the attacked tree start drying till it becomes unproductive. Within a few years, the tree is dead. The pest can be located from the frass that comes out of the holes in the branches or in the main trunk. There may be more than one such hole, indicating multiple damage.
Control:
(i) Collect and destroy the grubs and beetles, and
(ii) Since the pest feeds inside the woody portions no insecticide spray can be effective. The only sure way to get rid of this pest is to locate the feeding holes, clear the passage and inject contact poisons or even diluted phenyle. Insert in the holes cotton wicks soaked in dichlorvos (0.1%) or dimethoate (0.03 %) or methyl demeton, phosphamidon or thiometon (all at 0.025%) and seal with mud.
3. Long-Homed Walnut Beetle, Batocera Horsfieldi Hope (Coleoptera: Cerambycidae):
The grubs of this beetle are a serious pest of walnut in Darjeeling, Kumaon hills, Kulu valley and Simla hills. The grubs are 90-150 mm long and pale yellow in colour. The beetles are 45-65 mm long, black in colour with fine ashy or yellow-grey pubescence. Their elytra have numerous shining black tubercles at the base and several rounded white marks extending up to the apex.
Life-Cycle:
The beetles emerge in June and July, and live for about 4 months during which period they mate and find suitable sites and lay eggs. The eggs are brown and oval, and are laid singly in the bark of the walnut tree. A female may lay 55-60 eggs in her life-time. The egg stage lasts 8-15 days.
The gubs at first feed on the bark and then bore inside the wood, completing their development in 20-25 months. There they remain in the pre-pupal stage for 50-182 days and make puparia. Once it pupates the insect remains in that stage for 40-90 days. The life cycle is completed in 23-32 months which is spread over 2-3 winters.
It has been noticed that if the grub is already full-grown before the on-set of winter, it remains quiescent from October to March. The younger grubs which are less than one year old, however, continue to feed slowly during the winter also.
Damage:
The young grubs feed on the inner side of the bark making zig-zag tunnels. Later on, the grubs bore down to the surface of sap wood and go even further into the centre of the wood. The attacked timber trees become useless except as fire wood, which hardly fetches the cost of cutting and marketing the wood.
Control:
(i) Hand picking and mechanical destruction of grubs and adults checks the population of the beetle.
(ii) Plug the live holes with cotton soaked in kerosene, petroleum or EDCT mixture and then plaster them from outside with mud.
4. Defoliating Beetles:
In north-western parts of the Indian Sub-continent, there are many species of nocturnal beetles that defoliate a large number of plants in the summer. Apart from the forest nurseries and ornamental plants which they damage, the pome fruit-trees also fall prey to the ravages of beetles. The damaged leaves present a characteristic sieve-like appearance on account of the shot- holes. Several species have been recorded in the western Himalayan and adjoining regions (Table 19.1).
Life-Cycle:
Not much is known about the life-histories of these insects. Presumably, they feed in the grub stage on humus, roots of grasses, weeds and other forest plants. The life-cycles are completed in one or sometimes more than one year. The adult beetles are known to defoliate fruit trees, causing serious damage to the young flowers. The damage is most severe on the marginal trees of an orchard. The newly planted trees close to forest areas are also more severely damaged.
Control:
Spray 2.5 kg of carbaryl 50WP in 1250 litres of water per ha as soon as the damage is noticed. The spray should be done in the evening and repeated after 7 days if the damage continues or if the insecticidal deposit is washed away by rain.
5. Codling Moth, Cydia Pomonella (Linnaeus) (Lepidopiera: Tortricidae):
The larvae of the codling moth cause the heaviest damage and are probably the most notorious of all the apple pests. It is widely distributed throughout Europe, North America, Australia, Baluchistan and Ladakh. In addition to apple, the pear fruits sometimes suffer rather severely from the attack of the larvae. The fruits of quince, walnut and of many wild species of Pyrus may also be damaged.
The full-grown larvae are 16-22 mm long and are pinkish or creamy-white in colour with a brown head. They have eight pairs of legs. The adult moth is small, about 12-14 mm in wing span and is 6-8 mm long. The fore wings are dark greyish and are marked with wavy lines and a copper coloured metallic eye like circle towards the outer margin. The hind wings are pale grey.
Life-Cycle:
The adult moths appear from the end of May to June. They fly at dusk and spend the day at rest on the trunk, branches or leaves of the apple trees. Being cryptic in colour they are difficult to detect.
The females, after pairing, lay white coloured eggs singly on young fruits, leaves and the twigs. The eggs are small, 1 mm in diameter, oval and very flat, appearing, in fact, more like small shining scales than the eggs of an insect. A single female may lay about 100 eggs in her life time.
After a period of 4-12 days the young larvae emerge from the eggs and enter the fruit usually through the calyx. Having penetrated into the apple fruit, the larva attacks the core and the flesh around, burrowing further to the centre and the tips, which may also be eaten. After a period of three weeks to one month, the larva is full-fed.
At this stage the larva burrows its way out of the apple fruit and falls to the ground. It seeks shelter in cracks or crevices in the bark of the apple trees and having chosen a proper position, it spins a silken cocoon in which it transforms into a yellowish-brown pupa. The pupal period is completed in 8-14 days.
The second brood moths give rise to larvae that attack the apples in the same way as the first brood, though they usually enter the fruit through the side instead of through the calyx. Like the first brood they spin cocoons in which to pass the winter, pupating the following spring and producing moths in due course. In cooler regions, there is only one generation, but in warmer areas there are two generations in a year.
The Indian house-sparrow, Passer domesticus indicus, devours a great number of the hibernating larvae. The larvae are also parasitized by Paralitomastix varicornis Nees.
Damage:
Damage is caused by the larvae which burrow into the fruit and feed on the pulp. The infested fruits lose their shape and fall off prematurely. These fruits cannot be marketed for human consumption.
Control:
The control measures are same as in case of tent-caterpillar. Strict quarantine measures should be adopted to check the spread of this pest to other apple growing areas of the country.
6. Apple Fruit Moth, Argyresthia Conjugella Zeller (Lepidoptera: Yponomeutidae):
It is a pest of common occurrence in Asian, European and American countries falling in the isotherm range of 0 to ± 10°C. In India, though it is present in Himachal Pradesh for over five decades in dry temperate region of Kinnaur within altitude of 2445-2900 m, its identity was authenticated in 1985.
The possibility of its occurrence in high altitude of Kashmir cannot be ruled out. Short statured trees of vigorous growth and bushy crown with profusely developed leaves are conducive to apple fruit moth activity, as such Golden Delicious is the most preferred cultivar followed by Red Gold, Royal Delicious, Red Delicious and crab apple.
Life Cycle:
It is a univoltine pest and overwinters in pupal stage which lasts for about 290 days. Moths start emerging in June and emergence continues for about a month, when fruit is about 3 cm in diameter. The moth lays eggs in small clusters. The neonate larvae may enter the fruit from any side but calyx end is preferred.
On the entrance hole a crystallized white deposit is formed. The larvae mine in the gallery in the young developing fruit to reach the core and in core it enters into the seed. First, it feeds on perisperm for 2-4 days, then enters cotyledonous part and undergoes first moult. Subsequent 3 instars feed on cotyledons and occupy whole of the seed.
It becomes full-fed in about 3 weeks inside the seed and then makes a hole on the testa and after 2-3 days, matured larva tunnels an outgoing gallery ending into an exit hole of about 1 mm diameter on the fruit surface. Then, it drops to the ground for pupation. It pupates under soil, stones or ground litter in thick two layered silken cocoon and overwinters in this stage till next summer.
Damage:
The larva of the apple fruit moth makes tunnels in the apple, in search for the seeds. The apples get a bitter taste and rot in advance. An orchard with a lot of infested fruit left on the ground can contribute to the buildup of pest population.
Control:
Two sprays with 4.5 litres of chlorpyriphos 20EC or 2.5 litres of quinalphos 25EC or 2.0 litres of malathion 50EC in 1250 litres of water per ha are effective in suppression of the infestation. The first spray should be applied on first visible symptoms and the second fortnight later.
7. Walnut Weevil, Alcidodes Porrectirostris Marshall (Coleoptera: Curculionidae):
This is the most destructive pest of English walnuts (Juglans regia L.) in the Himalyan region at altitudes of 1,000-2,450 metres and has been reported as a serious pest in Kumaon, Kulu and Kashmir. No other host of this insect is known.
The adults feed on buds and flowers but the grubs feed inside the fruits and are extremely destructive in causing premature dropping. The adult weevil is about 10 mm long, pitches black when young, and turns dark brown with age. There is a prominent snout in front which is somewhat straight and is directed downwards. The grub is legless, with a pale-brown head and measures 15 mm in length. Fruits with spots of dark brown or black resinous excretion harbour the grubs inside.
Life-Cycle:
This pest is active throughout the warm weather and passes the winter (from November to March) as an adult hiding in debris, under stones, under the bark of trees, and in cracks and crevices in the ground. Depending upon the altitude and the weather in a locality, the weevils become active in April and their activity generally coincides with the appearance of flower-buds. They feed on flowers, leaf-buds, tender shoots or young fruits.
As the fruits are formed, the weevils puncture them, laying more than one egg. As many as 15 eggs have been noticed in one fruit. The punctures on the young fruits are circular and on older fruits, they are crescent or irregular. The eggs hatch in one week and the creamy white tiny grubs bore deeper, feeding on the kernels. The grub is full-grown in 13-22 days and pupates inside the fruit.
The pupa is creamy white and is transformed into an adult in 9-17 days. The adults emerge from the fruits by biting roundish holes. They start the second generation and when weevils of this generation appear in September, the walnut fruits are almost mature. The adults feed on tender leaves and twig up to the autumn and then hibernate. There are two generations in a year.
Damage:
In the Kulu valley, the pest is most destructive at altitudes of 1,000-2,450 metres. The grubs feed exclusively on walnut kernel and reduce it to a useless black mass, but the weevils feed on green twigs, petioles, flowers and young fruits also. The grubs are far more destructive than the adults and as a result of their attack, more than 50-70 per cent of the fruits drop off and even those which remain on the trees may be unmarketable. It is a common sight to see the ground under walnut trees completely covered with infested and fallen fruits.
Control:
(i) Collect and destroy the fallen fruits in May-June to check the population buildup of the pest.
(ii) Spray 2.0 kg of carbaryl 50WP in 1250 litres of water per ha at fortnightly intervals when the young fruits are being formed.