Mango is considered to be the king of all fruits in South Asia. India is the largest producer and exporter of mangoes in the world. India produces some 18.00 million tonnes of mangoes annually accounting for more than 40 per cent of the world output.
The area under mango is 2.50 million ha. The seedling varieties are very tall, whereas the grafted ones are short and commercially more acceptable. In addition to being sweet and succulent, the fruit is a rich source of vitamin A and also vitamin C.
There are a number of insect pests of this fruit and over 175 species of insects have been reported damaging mango tree but the most abundant and destructive at the flowering stage are the mango hoppers. It is almost a necessity to control these pest species otherwise there is a heavy fruit drop and the trees may remain without any fruit.
1. Mango Hoppers, Idioscopus Clypealis (Lethiery); Amritodus Atkinsoni (Lethiery) (Hemiptera: Cicadellidae):
These are the most destructive pests of all the varieties of mango. Three species of mango- hoppers recorded as pests are Idioscopus clypealis (Lethiery), Amritodus atkinsoni (Lethiery) and I. niveosparus (Lethiery). They are widely distributed in India, Malaysia, Indonesia and Formosa. No alternative host plants of these insects are known.
Injury is caused by nymphs and adults, when they suck cell-sap from the inflorescence and tender shoots. The nymphs of I. clypealis are dull yellow or dust yellow, whereas those of A. atkinsoni are pale yellow, elongated and more active. Adults of the larger mango-hopper, I. clypealis, measure 6.3 mm length and are greyish.
There are three dark brown spots on the head, a median band and two black spots on the pronotum. The black triangular marking on scutellum and a central longitudinal dark streak dilated anteriorly and posteriorly, are the characteristics of this species. A atkinsoni adult is about 5.1 mm long. It differs from the larger species by the absence of a central longitudinal dark streak on the scutellum.
Life-Cycle:
This pest is active practically throughout the year but during the hot months of May-June and the cold months of October-January, only the- adults are found sitting in thousands on the bark of trunks, branches, etc. The adults surviving winter emerge in February from underneath the bark of trees and other places of shelter. They cluster on the floral buds and start sucking the cell-sap.
When the inflorescence appears, they start laying eggs in them in the second or third week of February and continue to do so for some weeks. The eggs are deposited singly and since they are embedded in plant tissues, it is extremely difficult to observe them under natural conditions. A female deposits, on an average, 200 eggs, a moderate temperature being more conducive to egg laying.
Within 4-7 days, the eggs hatch and the newly emerged nymphs are first seen at the end of February or in early March. They commence feeding on the inflorescence, quickly suck the cell-sap and excrete honeydew, which serves as a medium for the development of sooty mould, Chaetothyrium mangiferae. This gives a dull blackish look to the mango trees. The smoky-black appearance persists for many months until the fruits are mature and the crop is almost over.
By the time the majority of nymphs are mature, the fruit has set. The nymphs then migrate to the stems and the young leaves, and become full-grown in three stages, in 8-13 days. The full-fed nymphs then moult and give rise to winged hoppers. The life-cycle, from the time eggs are laid to the time the adults appear, takes 15-19 days.
The adults are mostly seen congregated on the lower portions of branches and trunks. During the hottest period of summer, they congregate in the shade of large mango groves. There is no feeding or egg-laying in May-June, but the insects remain very agile and hop readily at the slightest disturbance.
A second cycle of brood-rearing starts with the monsoon. Eggs and nymphs of this generation are found during July-August in the submontane districts of the Punjab. Adults of this generation emerge in September and they hibernate during winter.
The natural enemies associated with mango hopper, I. clypealis are Isyndus hews Fabricius, Epipyrops fuliginosa Tams (Epipyropidae) and Pipunculus annulifemur Bruvelli.
Damage:
Mango hoppers are the most destructive pests of fruit trees. Injury to the inflorescence and young shoots is caused by egg-laying and feeding. The voracious feeding nymphs are particularly harmful. They cause the inflorescence to wither and turn brown. Even if the flowers are fertilized, the subsequent development and fruit-setting may cease.
In thick and protected gardens where the atmosphere is humid, a sooty mould develops on patches of honeydew exuded by the nymphs. As the wind blows, young fruits and dried inflorescences break off at the axil and fall to the ground. The growth of young trees is much retarded and the older trees do not bear much fruit. Damage to the mango crop may be as high as 60 per cent.
Control:
(i) Do not go for high density planting as it provides favourable habitat for hopper multiplication.
(ii) Do not encourage plants to put intermittent flushes by regular irrigations and split doses of nitrogenous fertilizers.
(iii) Avoid waterlogged or damp conditions.
(iv) In case of old dense orchards, prune some of the branches during winter to have better light interception.
(v) Spray 2.5 kg of carbaryl 50WP or 2 litres of malathion 50EC in 1250 litres of water per ha, once in end of February and again in end of March. Spraying with malathion LVC @ 1.4 litres per ha with aerial or ground equipment is also effective.
2. Mango Mealybug, Drosicha Mangiferae (Green) (Hemiptera: Margarodidae):
The mango mealy-bug is widely distributed in the Indo-Gangetic plains from Punjab to Assam. Besides mango, it also attacks 62 other plants, including such trees as the jack-fruit (Artocarpus heterophyllus Lam.), the banyan (Ficus bengalensis), guava (Psidium guajava L.), papaya (Carica papaya L.), Citrus spp. and jamun (Syzygium spp.)
Damage is caused by nymphs and wingless females which are oval, flattened and has body covered with a white mealy powder. The males have one pair of black wings and are crimson red.
Life-Cycle:
This pest is active from December to May and spends rest of the year in the egg stage. The eggs are generally deposited in April-May in soil up to 15 cm within silken purses. The dead body of the female is often found sticking to them. In the crevices or in loose soil, the egg purses may be found as deep as 60 cm.
The eggs, 1 mm long and 0.7 mm broad, are oval, shining pink when newly laid and become paler later on. They hatch at the end of December or in January and, in a given locality, continue to hatch for about one month. Thus, the nymphs appear before the fresh growth of flowers on mango-trees.
It has been recorded that 70-80 per cent of nymphs ascend the trees immediately. The remaining 20-30 per cent wanders about, feeding on weeds and general undergrowth in the orchards. They also ascend the trees and while ascending, they are found clustering near the lichen patches on the bark.
Eventually, they congregate on the panicles where they feed on the ceil-sap and pass through three stages. The duration of the first stage runs from the middle of December to early February; of the second stage from February to the middle of March and that of the third stage from March to April.
At the time of moulting the younger nymphs wander away from the original feeding places in search of suitable shelters such as cracks and crevices in trunks. After moulting, they again seek suitable feeding-sites. The third- stage nymphs, however, stick to their original feeding places and those destined to be females, continue feeding.
Mating takes place soon after emergence of the males at a time when the females are not fully developed. The males fly about in large numbers, apparently in search of their mates. They have a very strong sex instinct and during the life-span of about one week they mate frequently. The females mature after 15-35 days and lay eggs for 22-47 days during April-May.
The nymphs are parasitized by Phygadeuon sp. (Ichneumonidae), Getonides perspicax Knal, and larvae of Brinckochrysa scelestes (Banks) (Chrysopidae) and grubs of Rodolia fumida (Mulsant) (Coccinellidae) are predaceous on this mealy-bug.
Damage:
Among insect pests of mango, the mealy-bug occupies an important place, second only to the mango-hoppers, with respect to the amount of damage caused. Only the nymphs are destructive and they suck plant juice, causing tender shoots and flowers to dry up. The young fruits also become juiceless and drop off. The pest is responsible for causing considerable loss to the mango growers and when there is a serious attack, the trees retain no fruit at all.
Control:
(i) Remove weeds from orchards which act as additional hosts for mealy bug.
(ii) Ploughing of orchards during summer exposes eggs to natural enemies and extreme sun heat.
(iii) Nymphs should be prevented from crawling up the trees by applying 15-20 cm wide sticky bands with alkathene or plastic sheets around the trunk about one meter above the ground level during second week of December.
(iv) The nymphs found congregating below the lower edge of alkathene band should be killed mechanically or by applying 50 g of methyl parathion 2 per cent dust.
3. Mango Stem Borers, Batocera Rufomaculata DeGeer and B. Rubus Linnaeus (Coleoptera: Cerambycidae):
Both these species of beetles have a wide range of distribution in India. They have been recorded as serious pests of mango, fig and other trees in northwestern parts of the Indian Sub-continent.
Damage is caused by the grubs, killing a branch or the entire tree, depending upon the place which they bore. The full-grown larva is a stout, yellowish- white, fleshy grub, measuring about 6 cm in length. Its head is dark with strongly developed mandibles. The adults are longicorn beetles, well built, large and pale greyish, measuring about 5 cm in length and 2 cm in breadth.
The first named species is slightly larger than the second. The beetle is provided with long legs and antennae and a dirty white band, extending from the head to tip of the body on each side. A number of dirty yellowish spots are present on the elytra. The head is distinct, with large prominent eyes, and the pronotum is ornamented with two crescent orange-yellow spots.
Life-Cycle:
The life-cycle is prolonged and the adults generally appear during the monsoon. They deposit eggs under the loose bark in a wounded or diseased portion of the trunk or a branch. The grubs are equipped with strong biting mouthparts and they penetrate into the stem or even the roots, feeding on woody tissues. Winter is passed in the grub stage in that very burrow.
They again start feeding as soon as the weather warms up in spring and during the feeding process, they bore through the wood by cutting large galleries. The full-grown larvae then hollow out a cell for pupation. The larval stage probably lasts more than a year and the pupal stage lasts about one month. The life-cycle may be completed in 1-2 years.
Damage:
Although the borer is not very common, yet whenever it appears in the main trunk or a branch, it invariably kills the host. Though the external symptoms of attack are not always visible, the site can be located from the sap or frass that comes out of the hole. The mango stem- borer is also found in newly fallen trees.
Control:
(i) Cut and destroy the infested branches with grubs and pupae within.
(ii) Remove frass near the holes on main stem and inject 4 ml of methyl parathion 50EC mixed in one litre of water into the hole and plug it with mud. In case these holes open, these may be treated again.
4. Mango Stone Weevil, Stemochetus Mangiferae (Fabricius) (Coleoptera: Curculionidae):
This is a short stoutly built, ovoid, dark brown weevil which is found inside the stone of mango fruit or in its pulp. It is widely distributed throughout the tropics. The export of mango fruits from India to the USA has been banned to prevent the entry of this weevil.
Life-Cycle:
The weevils are inactive from July-August onwards when they remain concealed in the soil or underneath the bark of mango trees. They become active as soon as the formation of mango fruits takes place. The weevils lay eggs in the skin or ripening fruit. The wound caused by the ovipositor heals soon after and the fruit does not exhibit any outward sign of infestation. On emergence from the egg, the grub moves further inwards, eating its way through the unripe tissue until it bores into the embryo of the mango- stone.
When full-grown, the larva forms a cell inside the stone in which it pupates. The weevil cuts its way through the stone and the pulp comes out. The generation is completed in 40-50 days, but the emerging adults become inactive and resume breeding only in the next season. Thus, there seems to be a single generation of this pest in one year.
Damage:
The insect attacks mango varieties with a relatively soft flesh. However, it is not very serious in any part of the country. The injury caused by the larvae feeding in pulp sometimes heals over but a certain number of fruits always get spoiled when the weevils make an exit through ripe or near-ripe mangoes.
Control:
(i) The pest can be suppressed by destroying all fallen fruits, weeviled mangoes and by disposing off refuse, stone, debris, etc.
(ii) The weevil, being an internal feeder throughout its development, is not amenable to control with any of the insecticides.
(iii) Raking of soil below the tree in October/November and March can contribute partially to weevil management.
5. Mango Fruit Fly, Bactrocera Dorsalis (Hendel) (Diptera: Tephritidae):
The mango fruit-fly or the Oriental fruit-fly is the most serious of all fruit-flies and is widely distributed in India and South-East Asia. It has also been recorded in Malaysia, Indonesia, Formosa, the Philippines, Australia and the Hawaii Islands. In many countries, it has displaced the Mediterranean fruit-fly, Ceratitis capitata (Wiedemann). Apart from mango, the pest also feeds on guava, peach, apricot, cherry, pear, chiku (Achras zapota), ber (Zizyphus spp.), citrus and other plants, totaling more than 250 hosts.
Damage is caused by grubs only and they feed on pulp, making the fruit unfit for human consumption. The legless maggots, when full-grown, measure 8-9 mm long and 1.5 mm across the posterior end, and are yellow and opaque. The adult is stout, a little larger than the ordinary housefly and measures 14 mm across the wings and 7 mm in body length. It is brown and has almost transparent wings with yellow legs and dark rust-red and black patterns on the thorax.
Life-Cycle:
This pest is active during the summer months and passes the winter (November to March) as a hibernating pupa in the soil. The adult flies emerge in April and reach ripening fruits and vegetables of the season such as guava, loquat, apricot, plum, brinjal, chillies, etc. Later on, they shift to mango.
The flies are most active in gardens when the temperature ranges from 25 to 30°C and they become inactive below 20°C. The adults live for about 4 months and feed on the exudations of ripe fruits and the honeydew of various insects. Mating takes place at dusk and lasts an hour or more. When flies are 10-15 days old, they lay 2-15 eggs at a time in clusters, 1-4 mm deep in the soft skin of fruit, with the help of sharp ovipositors.
A female lays, on an average, 50 eggs but under favourable conditions, 150-200 eggs are laid in one month. The eggs hatch in 2-3 days in March- April and 1-1.5 days in the summer and 10 days during winter. As the maggots develop they pass through 3 stages in the ripening pulp and are full-grown in 6-29 days.
They leave the fruit and move away by jumping in little hops. On reaching a suitable place, they bury themselves into the soil and pupate 8-13 cm below the surface. In 6-44 days, they emerge as flies and reach the ripe fruit for further multiplication. The life-cycle is completed in 2-13 weeks and many generations are completed in a year.
In spring, the number of flies is quite small, but by successive breeding they multiply steadily. During June, there is a dearth of fruits and the flies resort to brinjal as the only food. During the monsoon, they shift to mango trees and increase in number enormously. During the winter, their population declines steadily. The autumn is another period of food shortage and the flies breed on ripe citrus, guava, etc.
The parasitoids associated with this pest are Opius compensatus Silvestri, O. persulcatus Silvestri, Biosleres arisanus (Sonan), O. incisus Silvestri and O. manii (Braconidae); Spalangia philippinensis Mill., S. afra, S. stomyoxysine Gir. and S. grotiuse Gir. (Pteromalidae); Dirhinus giffardi Silvestri (Chalcididae); Pachycrepoideus dubiers Ashmead and Trybliographa daci Weld (Eucoilidae).
Damage:
Maggots are very destructive and cause heavy losses to all kinds of fruits. The infested fruits become unmarketable and at times almost all of them contain maggots.
Control:
(i) Avoid infestation of fruit flies by early harvesting of mature fruits.
(ii) To prevent the carry over of the pest, collect and destroy all fallen infested fruits twice in a week.
(iii) Plough round the trees during winter to expose and kill the pupae.
(iv) Monitor the fruit-fly population in orchards by using methyl eugenol traps.
(v) Spray 1.25 litres of malathion 50EC + 12.5 kg gur or sugar in 1250 litres of water per ha und repeat sprays at 7-10 days interval if infestation continues.
(vi) After harvest, dip the fruits in 5 per cent sodium chloride solution for 60 minutes to kill the eggs, if any and also to decontaminate them of insecticide residue if at all present.
6. Mango Shoot Borer, Chlumetia Transversa Walker (Lepidoptera: Noctuidae):
The adult is a small greyish brown moth. Young caterpillars are yellowish orange in colour with characteristic dark brown prothoracic shield. Full grown caterpillars are dark pink, with dirty spots.
Life-Cycle:
Eggs are laid singly on tender leaves and they hatch in 2-3 days. Freshly hatched caterpillars bore into mid-ribs of tender shoots near the growing point tunnelling downwards and throwing their excreta out of entrance hole. Larva has five instars completed in 11-13 days. The full- grown larva enters into slits and cracks in the bark of tree, dried malformed inflorescences or cracks and crevices in the soil for pupation for 12-15 days. The life-cycle occupies 30-42 days. Larva is parasitised by Bracon greeni.
Damage:
Damage is done by the larvae by boring into the growing shoots. Leaves of affected shoots wither and droop down. Young grafted seedlings are severely affected and may even be killed.
Control:
(i) Remove and burn the dried shoots, and
(ii) Spray the new growth with 2 litres of malathion 50 EC in 1250 litres of water/ha.
7. Mango Gall Psyllid, Apsylla Cistella (Buckton) (Hemiptera: Psyllidae):
This insect appears occasionally as a serious pest in several parts of North India. The adult psyllid is 3-4 mm long with black thorax and head, and light brown abdomen.
Life-Cycle:
Eggs are laid partly embedded within the midribs on the lower side of the tender new leaves. Up to 150 eggs are laid by a female during February to April. Nymphs appear during August and September. They feed on the vegetative and reproductive buds causing the formation of cone shaped galls on them. Gall formation is noted in September and October. The nymphs become adults within the galls, the nymphal period lasting for about five months. The adults appear in end of March and one generation is completed in a year.
Damage:
The damage is caused by the nymphs who feed on vegetative and reproductive buds. The attack causes malformation of affected parts and reduces fruit set.
Control:
(i) Collect and destroy the galls, and
(ii) Spray 1.70 litres of dimethoate 30EC or 1.85 litres of monocrotophos 36SL in 1250 litres of water/ha.
8. Mango Bud Mite, Aceria Mangiferae Sayed (Acari: Eriophyidae):
The bud mite is a pest of mangoes not only in India but also in Pakistan and USA. In India, the mite is serious particularly in Punjab, Haryana and Uttar Pradesh.
Life-Cycle:
The detailed life-history of this eriophyid bud mite has not been studied so far. Some observations on the population dynamics of the mango-bud mite have revealed that there is a seasonal variation in its population. In the Punjab, the highest population is found during February after which there is a gradual decrease until it becomes very low in May.
There is again an increase in population in June and another peak in July. In August-September, there is a further decrease in population which remains low during October-December. A rapid increase in January results in the peak population being reached in February, which coincides with the maximum new malformation, hence the suspicion that the two are related.
Damage:
The bud mite sucks the sap from inside the buds and causes necrosis of tender tissues. When the population is high, the entire bud may be killed. This mite infests all varieties of mango and none has shown resistance to it.
Control:
(i) Remove and destroy all the panicles bearing infested inflorescences.
(ii) Spray one litre of dimethoate 30EC in 1250 litres of water per ha, preferably during summer.