Here is a list of insects that damage fruits and fruit trees: 1. Sanjose Scale Aspidiotus Perniciosus 2. Woolly Aphid – Eriosoma Lenigerum (Haussmann) 3. Fruit-Sucking Moths (O. Materna) 4. Citrus Leaf-Miner (Phyllocnistis Citrella) 5. Lemon Butterfly (Papilio Demoleus) 6. Anar Butterfly (Viracholaisocrates Fabr.) 7. Singhara Beetle (Galerucella Birmanica Jac.) 8. Banana Weevil (Cosmopolites Sordidus) and Few Others.
1. Sanjose Scale Aspidiotus Perniciosus:
This important member of the scale insect family Coccidae is believed to be a native of China but today it has spread to practically all parts of the world where deciduous fruits are grown. It is believed to have been got introduced into India first in Jammu and Kashmir State where some flowering plants were imported for garden decoration and the same happened to be infested with this insect.
This pest (Quadraspidiotus perniciosus Comstock) owes its common name to the city of Sanjose in California, U.S.A.; it first attracted serious attention in 1873. Its seriousness, however, was first realized only in 1922 and systematic survey carried out during the late thirties and early forties showed that it had already spread to all the fruit-growing areas not only in north India but also in south India.
This pest has a very wide range of host plants the number of which runs up to 200 belonging to nearly 28 plant families; all the same, it appears to have special preference for the members of the plant family Rosacea. The seriousness of this species can be gauged from the record that in 1922 more than 1,000 acres of mature apple trees were killed in southern Illinois due to infestation by this pest.
Each insect is pretty tiny with still tinier sucking mouth-parts with which it sucks the plant sap, but its numerical strength often reaches such proportions that even big trees succumb to its damage. Lightly- infested trees show greyish specks on the surface and at times there is a reddened area around each speck particularly on young shoots; but in cases of heavy infestation, the entire surface of the bark is covered with a grey layer of overlapping scales and appears as if the branches have been sprinkled with wood ash when wet.
With such a constant drain on the plant-sap, it is but natural that the whole plant gets de-sapped and death of the tissues starts from the periphery. At times, even the fruits get infested and look specky and thus adversely suffer in their market value. If a twig lightly infested with the Sanjose scale is examined under a magnifying lens particularly early in spring it will be found to be studded with two kinds of specks or scales as they are called.
The one which is a female scale is almost round in shape with a raised nipple like projection in the center and the other type which is the male scale is rather elliptical with a nipple-like projection situated in the wider region of the scale. The former remains scale-like throughout but from the latter comes of out a two-winged male insect. Thus, there is a very distinct sexual dimorphism in the species.
During winter season the Sanjose scale developed partly in nymphal stages, which remain tightly, stuck to the bark under the two types of scales described above. During spring, these nymphs being to develop quickly depending on the temperature and soon winged male adults emerge and mate with females, which also by this time have moulted a number of times and have become mature without shifting from the points where they had remained from the very beginning of their nymphal life.
These females are ovoviviparous, i.e., their eggs develop within the body of the female and the young nymphs emerge out from within the female scale. Each female can continue to reproduce in this way for several weeks, depending on the temperature. These young ones are very small and they crawl about over the surface of the plant- twigs for a short time till they find a suitable place where they insert their sucking mouth parts and begin to suck the plant sap.
Nymphs at this stage are also called crawlers. From now onwards these creatures become stationary- the female for the whole life and the male till it transforms itself into a winged adult. At the very first moult, which occurs after about 10 to 12 days, the nymphs lose their legs and antennae and thus lose the power of locomotion. During spring and summer, the whole nymphal period can be completed in about a month or so and there can be a number of generations from early spring to late fall when dormancy starts.
The mortality of the over wintering population is often quite appreciable. It is reported that although scales enter in to hibernation in various stages of growth only those survive the winter, which have reached the size of 1/8 cm and have secreted grey scales over themselves. All other stages invariable perish during the winter.
From the above account it is clear that the intrinsic power of locomotion and spreading is very limited, in this pest; all the same, it has spread quickly all over the world. Transcontinental spread takes place through human agency carrying infested stock from place to place. Local spread is brought about accidentally, by the crawler, on the bodies of birds and other larger insects or also by air currents with which the crawlers can be blown about.
Being stationary for the major part of its life, this pest has a very large number of natural enemies in the form of insect parasites, parasitic, fungi, insect predators, bird predators, etc. All these, together, exert a considerable check on the population build-up of the pest. All the same, unaided by human agency, these natural enemies are not able to keep the pest below economic level particularly in the regions of temperate fruits.
During the last two decades, a number of highly toxic chemicals have come into the market, which can be used during the full-growing season without any fear of phyto-toxicity and, which are quite effective against the Sanjose scale. These sprays are now so popular that it is at times difficult to check the growers from treat in their orchards. The only serious problem now is that this pest attacks such a large variety of fruit and forest trees that it is not possible to carry out chemical control on all the alternate hosts.
The result is that chemical control proves to be a very temporary palliative as the infestation on the uneconomic trees surrounding the fruit orchards is always very heavy and therefore the good effect of the chemical control is very soon lost. The result is that orchards have to be treated again the again during the same season. In order to over-come this difficulty, it is highly advisable to integrate chemical and biological control for keeping this pest economically under control.
It is advisable to treat the orchards of valuable fruits like apple, etc., by means of suitable insecticides and to carry out intensive biological control if the pest in the surrounding area of such trees as cannot be economically treated with insecticides. In areas like Kashmir, it is highly feasible that a parasite like Prospeltella sp., be reared in very large numbers in specially heated rooms during the whole winter seasons.
The population can be rapidly built ten to twenty-fold during each generation of about four weeks and then the areas covered with the comparatively small over wintering population of Sanjose scale on uneconomic plants can be flooded with these parasites which can keep down the infestation inoculum in these areas around the fruit orchards.
In this way, the infestation from outside the orchards can be very effectively checked, resulting in a reduced number of sprays in the orchard itself. This is a very fertile field for an effective and fruitful integration of chemical and biological control both of which can be applied simultaneously in time but in distinctly separate areas.
2. Woolly Aphid – Eriosoma Lenigerum (Haussmann):
The wooly aphid, releases a kind of white powdery secretion by its numerous glands on the body which gives a general appearance of cotton wool covering often large colonies of this aphid pest, the adult body colour of which is actually purplish.
This is a very serious pest in practically all the temperate regions and pockets of the world where temperate fruits are grown. Although it attacks a number of fruit trees, its seriousness of different species differs from region to region. In India, it has been a very harmful pest of apples ever since it was introduced into this country via Britain sometime in the beginning of the present century; it is considered to be native of America.
The nature of damage caused by this aphid is essentially similar to what has already been described in the case of the mustard aphid but the distinctive feature of the damage by the woolly aphid is that it takes place in a very large measure even in the root region where it is very difficult to control.
The in infestation in the aerial portions of the plant is spread to all parts like the trunk, the stem, the branches, and tips of twigs, fruit stocks, leaf petioles, etc. Their infestation is often associated with the information of various kinds of deformities, large knots, etc., both on underground and above ground portions but this association can also be due to the fact that at times these aphid colonies cluster in wounds resulting from ‘her causes.
All other symptoms due to de-sapping of the plant, like a sickly appearance, a stunted size, loss of vigor, etc., are also produced and the fruiting capacity of the tress is very much reduce. The infestation in the underground portion, at times results in such a severe disintegration of the roots that the trees gets uprooted by winds.
The life-history of this pest is quite interesting and adaptable varying in detail from place to place obviously depending on the climate of the place. The overall simplified picture of the life history is somewhat as follows- the pest overwinters generally in two stages, i.e., either as eggs or as immature nymphs on the underground portions of the host plant. The eggs hatch and the nymphs mature during spring when active development and breeding start, depending on the temperature.
The form of reproduction in this season is by parthenogenesis and vivipara, i.e., the females reproduce without mating with males and they give birth to young once instead of laying eggs. The nymphs soon settle down to feed on the plant-sap and within 24 hours thereafter begging to secrete the woolly filaments of wax over their body.
They undergo four moults before they become adults and this process may be so quick as to take only about 10 days, although this period may get lengthened to near-about 100 days when it is very cold. During the whole of summer and the monsoon, the reproduction is very rapid and both winged and wingless forms are found. There is considerable dispersal of the pest at this time both by the flying of winged forms and by passive dispersal of wingless forms either due to wind or on bodies of larger animals.
There is also considerable migration form the aerial region to the root region and vice versa. During fall and particularly when approaches winter, the sexual forms appear, mate and lay eggs. Also at this time, there is migration form the aerial region to the root region for hibernation in nymphal stages, to make themselves safer and also to make their predators difficult.
The variations recorded from place to place which are obviously due to variations in the climate are with respects to migration from the aerial region to the root region and vice versa, production of sexual and oviparous forms, niches in which over wintering takes place, etc. These variations are more or less on expected lines. For example, where one-sided partial migration between aerial and underground regions takes place, it is from root to shoot in spring and vice versa in fall or winter.
This is quite easy to understand and quite purposive in nature. In other places like the Kurrum valley, hibernation takes place in viviparous female forms, which remain lurking under loose barks of trees and other crevices and which come out of these shelters in spring and go back to the same if a cold spell come up again.
Where winged forms are not found during summer, they are produce during the fall, obviously for securing winder dispersal and ensuring greater chances of survival during winter. Thus on the whole, it appears that quite interesting and fruitful results are expected if the bionomics and ecology of the woolly aphid are studied from this angle.
Eriosoma lanigerum like other aphids has also a number of natural enemies in the form of parasites and predators. What is special about this pest is that its economic importance in India is reported to have been brought down from that of a very serious pest to that of an insect of very little significance and this tremendous change is believed to be the result of introducing an exotic parasite Aphelinns mali Hald from the original home of the pest.
Similar successes have been reported from several other countries as well where the pests have got introduced inadvertently and where the parasite was introduced as a planned attempt for biological control. As regards chemical control, the insecticides recommended in earlier days used to be rosin soap and nicotine preparations for killing the pest on the shoot and chemicals like paradichloro-benzene for fumigating the underground infestation. Now, however, there are a number of very powerful organ-phosphorus compounds, for aerial spray and also a number of systemic insecticides against root infestation.
3. Fruit-Sucking Moths (O. Materna):
The fruit sucking moths are quite large noctuid moths belonging to about twenty different species, the wing-span or some of them are about 1 cm or more. Generally, moths and butterflies damage the plant or plant products only during their larval stage but fruit sucking moths as their common name indicates damage fruits in their adult moth stage. These moths damage the outer skin and then suck the juice of fruits like the orange, guava, peach, pear etc.
This damage results not only in fruit fall but also exposes the fruits to a number of other insects’ fungi and bacteria due to which the fruits rot or at least severely suffer in quality because of the scar left on the fruit even if the wound caused gets healed up. Another very important peculiarity of practically all fruit-sucking moths in that their larvae feed on entirely different plants most of which grow wild and even quite far away from the fruit orchards.
The result is that the breeding of these insects takes place often outside the orchard and as the larval food is often of no economic importance, ordinarily nobody even takes notice of its breeding. This phenomenon makes the control of these pests especially difficult. Just as for the control of files and mosquitoes the attack has to be concentrated on their breeding places, these pests should also be rationally killed in their larval stages.
But there are two main difficulties: the first that it is difficult to spend as much on these pests as one can in the case of flies and mosquitoes which cause serious problems of human health and when it is so difficult to control those vectors of human diseases how much more difficult it will be to control these fruit pests; the second is that the food plants of larval stages of fruit-sucking moths are much more widely and sparsely scattered.
However, there is one point which should make the control of fruit-sucking moths in their larval stages slightly more feasible than mosquitoes and flies and that is that in the present case the larval food-plants have to be eradicated and this can possibly be tried with success if a concentrated campaign is organized on a really large scale.
The group of pests somewhat parallel to fruit-sucking moths is that of chafer beetles the larval stages of which are serious pests as white grubs and adults as serious pests on the foliage of fruit-trees. However, as white grubs and chafer beetles are both serious pests of economic crops, one is likely to be more inclined to spend on these pests.
The control, which is considered to be more feasible is the baiting of the fruit-sucking moths themselves. The attractants used for baiting purposes generally consist of fruit-juice mixed with crude sugar and water to which a suitable poison is added. This bait-mixture can be kept in wide-mouthed vessels so that the moths may be attracted to feed on this poisoned syrup and die. The success so far is only partial. The only rational approach is to take a realistic view and organize large-scale campaigns financed by orchardists as a co-operative venture.
Other aspects of the biology and life-history of these pests are fairly similar to those of any other noctuid pests. The moths lay eggs on the larval food-plants and the resulting caterpillars spend their life up to the pupal stage on or near their food-plants and the adults after emergence fly often quite long distances to feed on fruits in orchards of the area.
4. Citrus Leaf-Miner (Phyllocnistis Citrella):
The various species of fruit-trees belonging to the citrus family the leaves often show white glistening irregularly-zigzag galleries within the leaf lamina. The tunneling is done by the larvae of a moth named Phyllocnistis citrella commonly called citrus leaf-miner. Due to the extensive mining by the pest, the leaf suffers badly, gets deformed and irregularly curled up in shape, unhealthy in look and defective in its function and finally it dries and falls off.
At times, even the young shoot is attacked. Consequently, the whole plant suffers and also becomes prone to diseases like citrus canker. As expected, succulent leaves with thin epidermis are more suitable for the penetrating and mining activities of the tiny larva.
Hence, the attack is comparatively much greater in leaves of fresh growth, young seedling and varieties with characteristics of having soft succulent leaves. The adult stage is a tiny greyish moth with a wings-span of 8 to 10 mm. The forewings are white with two narrow grey stripes and the hind-wings have pale grey fringes. These moths’ lay minute flat eggs singly on the underside of leaves and these eggs may hatch out in as short a period as two days.
The larva as it hatches out is legless but it soon enters the leaf tissue and begins to feed inside it and mine the leaf lamina. The larval period may be as short as five days after which the larva comes out and pupates near the margin of the leaf which folds up to provide a sort of cover over the pupa. The pupal period can come to an end in about five days after which the moth come out and starts a new generation.
Thus, one generation can be completed within about two weeks. Although it can also sometimes take about two months, depending on the environment when all the developmental period given above get lengthened. This cycle of generations continues practically the whole year. However, the development slows down in the colder months and activity of the moth may cease in the months of December and January when it is very cold.
The control of this pest is not as easy as that of the external pests but also not as difficult as that of many internal feeders. This is so because the thin covering over the larval galleries is not very impervious. Hence, emulsions of insecticides, which are not phytotoxic, can be more useful. Sprays containing nicotine, parathion, etc., have been reported to be useful but emulsified formulations of somewhat more persistent insecticides are likely to provide a more prolonged protection and preventive cover.
5. Lemon Butterfly (Papilio Demoleus):
The lemon butterfly is very attractive and common butterfly with which everybody is bound to be familiar although few suspect it to be harmful in any way.
So much is common between moths, a number of which have already been described, and butterflies, to which group this insect belongs, that it is only necessary to point out a few differences. The most prominent difference between moths and butterflies lies in the pattern of the resting position of the wings, those of the moths being flexed laterally downwards in slanting roof-like disposition on either side of the body length while those of the butterflies are held juxtaposed over the back and perpendicular to the surface on which the insect rests.
The other important difference, which can be made out after a little close examination between the two groups of the same order is that the feelers or antennae as they are called, are club-shaped i.e., thick at the end in butterflies, while they are either filiform or pectinate in moths.
The third and economic difference is that while a very large number of moths are serious pests of crops and fruit-trees, the number of moths are serious pests is comparatively small in butterflies. Thus, the lemon butterfly is one of the fewer species of this group, which is quite harmful in its larval stage and an object of beauty and aesthetics in its adult stage, which lends charm to the environment, which it flits about.
The lemon butterfly is widely distributed in the Indian subcontinent and it is found right from Arabia in the west to Taiwan in the east. The food-plants of its larval stage include various species of citrus and also a number of other plant genera. The female butterfly lays yellowish- white eggs on young leaves and tender shoots. The eggs are scattered singly instead of being laid in batches.
These eggs hatch out within a couple of days into dark-brown caterpillars which eat the leaves of the citrus trees and which after a few days develop such irregular whitish markings on the body surface that they look as if they are not caterpillars but some irregular masses of bird excreta.
Obviously, this is a protective adaptation to escape the notice of their predatory enemies like birds who would not like to pick up their own droppings. It is, however, interesting that later on when almost full-grown, these caterpillars put on a green colour and move away in various directions and pupate while hanging from the twigs. One complete generations may take as little time as two-and-a-half weeks and as much as four-and -a-half months.
Generally, there are several generations during a year and the winter is passed in the pupal stage. As regards control, this pest can be picked up mechanically in larval and pupal stages if its population is low or when the attack has just started. In cases of severe infestation, there is no alternative to a chemical treatment with some strongly persistent insecticide having both contact and stomach poison effects.
6. Anar Butterfly (Viracholaisocrates Fabr.):
Glossy brown, violet blue or violet brown coloured flies measure about 2.5 cm. across the wing. They lay shiny white small conical eggs at the base of the flower, on the fruit, apical bud or leaf near the fruit. The eggs hatch within 7-10 days and the caterpillar bores inside the fruit attacks the seed and the pulp both.
The larval period varies from 17-45 days and the size about 2-2.5 cm. The larva comes out of the fruit and spins a silky web around the twig and the fruit and pupates on the fruits. The pupal period stands for 7-40 days. As many as 4 overlapping generations are found in a year.
Control- As in case of mango fruit fly.
7. Singhara Beetle (Galerucella Birmanica Jac.):
Damage is caused by the grub as well as by the beetle. They are active from July to September. The attacks in the leaf of the plant makes holes and inhibits the formation of fruit and flower. This lower down the yield of the crop.
The adult is blackish brown about 5-1 cm. long Elytra well developed. It lives in the mud or cracks or under the herbs in the dry part of the plant from where the water has receded. It hibernates the unfavourable weather in the mud and lays eggs on the seedlings of Singhara. The eggs are laid in clusters of 10-30 on the upper surface of the leaves. A female can lay about 100 eggs.
The incubation period is of 6-9 days and the grubs inhibit the growth of the plant and live in the buds or leaves of the plants. The grub is light brown and undergoes 4 mouldings within 20-22 days. The pre-pupal period is one -two days when the larva is very slow and stops feeding. The pupa is oval, orange red with dark brown patches on the body. Pupal period lasts for 5-7 days. There is 6 generation in an active year and a complete life cycle takes about 35-40 days.
Dusting BHC or DDT 5% or Carbonyl 10% on the crop after every 15 days saves the crop from the damage. Manual collection of the infestation also helps in pest control.
8. Banana Weevil (Cosmopolites Sordidus):
The weevil also known as banana borer bores into the corm of the plant and consumes the corm tissue. Thus kills the seedlings, but they never attack the root of the banana.
Distributed throughout India, South-East Asia, Australia and Hawaii islands, tropical America and Africa. This weevil is a notorious pest of Banana. The weevil is black or dark brown with club shaped antenna and well developed elytra. It lays 10-15 eggs in the self-made holes in the corm, which hatch within a week. The grub’s dark brown, yellowish brown with shiny brown head bores into the corm makes tunnel and feeds upon. It takes about 2- 6 weeks in attaining the full size. The pupation takes place outside the corm in and around the plant. The beetle comes out within 5- 7 days.
The infestation can be checked only by manual operation, by removing the infested corm and destroying the damaged portion. Full precaution should be taken during sowing new crop.
9. Mango Fruit Fly (Dacus Dorsalis Hendel):
It is most serious of all the fruit flies and is widely distributed in South-east Asia, India, Australia and other countries of oriental region. It not only attacks mango fruits but guava, apricot, plum peach, fig, apple etc. are damaged equally.
The maggot spoils the fruit. It makes a hole in the pulp/ on the skin and enters the fruit. The damage is so serious that fruits fall down prematurely. These maggots measure about 1 cm. in length and 1.5 mm. in width. These are yellow and opaque. They moult three times in the pulp and are ready to pupate in 6- 29 days. They leave the fruit and jump in the soil where they pupate 8- 12 cm. below the soil and emerge as adult within 6- 14 days.
The adult live for 3- 4 months and feed upon the fruit juice, honey due and other such juices available in the area. These are slightly bigger than housefly and reddish in colour with yellow and black markings. These are active in summer months and hibernate in winter. They mate in evening and lay 150- 200 eggs in batches of 2- 15 eggs per cluster. The egg laying is done 1- 4 mm. deep in the pulp of fruit. They hatch in 3-10 days depending upon temperature and humidity.
The soil below the plant should be ploughed deep and mixed with 10% DDT and BHC dust. The adult can be checked by spraying the plant before ripening of the fruit with 1% Malathion or dimethoate .03%. The fruits should be taken at least 15 days after such a spery. Infested fruits should be destroyed.
10. Bark-Eating Caterpillar:
In the garden we see a dirty, elongated zigzag, ribbon- like messy web consisting of bits of bark pieces, excreta etc., an inch or more in width and even up to two feet in length, covering the trunks and branches of trees of various species. At times, several such webs are found on each tree and their very presence gives and unhealthy look to it.
While trying to clear up this mess, one finds that these elongated webs cover a gallery of an inch or so in width leading at times to a hole generally in the angle of the thick branches and within this gallery or the hole a caterpillar is found generally unless one is dealing with an old abandoned gallery. This is commonly known as the bark- eating caterpillar and it is the larva of a large- sized moth which specialists will identify as a species of Indarbela (I. teraonis Moore, I. quadrinotata Walker).
The caterpillar is very harmful to the tree on which it is found because it feeds on the bark and in this process it seriously injures the plant tissues through which nutritive plant- sap is transported within the plant’s system; the result is that the tree- growth and fruit- bearing capacity are adversely affected. At times, the infested branches can dry up and in cases of severe infestation the whole tree may die. It is a peculiarity of this pest that it prefers older trees to younger ones. The infestation in some areas of the country has been reported to be more than 40 percent.
The life-history as worked out in a central region of India is somewhat as follows: The adult is a large- sized moth with a wingspan of about 4 cm in the female and about 3 cm in the male, light grey to light brick- red in colour and with dark brown patches or dots. The female lays a very large number of eggs but in small groups of 15 to 20 eggs each.
The egg- laying takes place in May and June and the incubation period is about 10 days. The caterpillar soon after hatching begins to feed on the bark and prepares the web under which it lives. The larval period is quite long and the caterpillar continues its destructive activity from May- June up to April the following year.
During this long period, it grows slowly being about 1.5 cm in September to about 4 cm by December when it is practically full- grown. The larval habit is quite important. It remains in hiding practically the whole day and comes out for feeding on fresh areas only during the night. From April onwards, the population starts.
It takes place within the larval gallery and the pupal period is only three to four weeks. At the end of the pupal period, the pupa wriggles up to the opening of the gallery where from the moth emerges, leaving the pupal skin fortuning from the exit hole. The moth’s life is quite short and it completes egg- laying within two or three days after which it dies.
The list of trees attacked by the bark-eating caterpillar is quite large and includes mango, guava, pomegranate, jamun, etc., which are commonly found in ordinary gardens. The main feature which should be fully exploited for its control is that its presence can be easily spotted out even from a distance due to the prominent web it makes.
Hence, the rational approach is to clean the web and fumigate the hole with an ordinary fumigant by putting in the hole a swab of cotton wool dipped in the liquid fumigant and inserting the same in the hole which should thereafter be plugged with mud.
Another somewhat simpler approach is to inject a strong persistent insecticidal liquid formulation into the web of the larva and also smear the same up to quite a distance outside the hole so that when the larva comes out in the night it may get poisoned. The insecticide should have both contact and stomach poison effects, and it should be as persistent and strong as possible.