Learn about the pests that damage tropical and sub-tropical fruits.
1. Coconut Scale, Aspidiotus Destructor Signoret (Hemiptera: Diaspididae):
Cocount scale is found in India throughout the plains and low hills, on a number of host plants including coconut, tamarind, avocado, banana, ber, citrus, datepalm, fig, grapevine, guava, jamun, mango, papaya, peach, pear, sapota, etc.
Two more scale species, namely Aonidiella orientalis (Newstead) and Aspidiotus tamarindi (Green) also infest the tamarind tree. Both the young and the adults of these insects suck cell sap. The affected parts are devitalized and there is premature shedding of buds and flowers, affecting ultimately the fruit setting capacity of the tree.
2. Citrus Mealybug, Nipaecoccus Viridis (Newstead) (Hemiptera: Pseudococcidae):
We have already learnt about this mealy bug which was observed in the pests of jackfruit.
Another mealy bug, Planococcus Lilacinus (Cockerell) (Hemiptera: Pseudococcidae) has been found mainly on tamarind and pomegranate. Both the adults and the nymphs are found in large numbers on the ventral surface on leaflets and the base of leaf petioles, on tender shoots and even on fruits. The pest causes damage by sucking the cell sap and devitalizing the plant. In case of severe attack the leaflets become chlorotic and fall off. There may also be immature fruit fall.
3. Mango Stem Borer, Batocera Rufomaculata DeGeer (Coleoptera: Cerambycidae):
Mango stem-borer is one of the most destructive pests of fig and is widely distributed in India, Sri Lanka, Malaysia and East Africa. In India, it has been recorded on more than 30 host plants including fig, guava, jack-fruit, mango, mulberry, pomegranate, walnut, etc. Since fig has a very soft wood this tree seems to be the greatest victim of this pest.
The grubs of this beetle bore into the main stem or branches without causing outward injury to the bark. Once inside, they make zig-zag tunnels in the wood. The affected stems show holes from which frass and chewed wood particles are seen coming out.
Ultimately, the branches dry up and in case the attack is on the trunk the growth and fruit bearing capacity of the tree are severely affected. The tree gives a number of new shoots below the attacked site but it ultimately dies. For details on its life-history see under ‘Mango.’
4. Fruit Flies, Bactrocera Dorsalis (Hendel) and B. Zonata (Saunders) (Diptera: Tephritidae):
Both these species are polvphagous and breed on a large number of host plants including many fruits and vegetables. In case of fig, only the over-ripe fruits that remain on the tree are attacked. The latex of the unripe fruits is not palatable to the grubs and the fruit-flies also avoid laying eggs on the young fruits. As a result of feeding by the maggots, the pulp of fruits becomes rotten and the fruits fall down.
5. Fig Mites:
Many species of mites have been recorded feeding on fig foliage. These include Aceria ficus (Cotte), Rhyncaphytopus ficifoliae Keifer and Eriophyes ficivorus Channa Basavanna (Eriophyidae); Melichares flci Narand Ghai (Ascidae); Cheletogenus ornatus (Canestrini & Farzago) (Cheyletidae); Eutetranychus hirsti Pritchard & Baker and Tetranychus neocaledonicus Andre (Tetranychidae).
All these are eight-legged spiders, very small creatures, which are seen moving among fine webs spun on the ventral surface of the leaves from where they suck cell sap. As a result of their attack, the affected leaves show blotches, turn downwards and ultimately they dry up and fall off. The severely infested trees may be seen almost denuded of the foliage.
6. Pink Waxy Scale, Ceroplastes Rubens Maskell (Hemiptera: Coccidae):
The pink waxy scale has been reported so far from East Africa, India, Sri Lanka, parts of China, Japan, Malaysia, the Philippines, Solomon Isles, East Australia, Pacific Islands, New Zealand and Hawaii.
It feeds on Citrus spp., jack-fruit, fig, mango, pear and other fruits. The adult females are 3-4 mm long and convex in shape. They are covered with a pink waxy shell often with vertical stripes. Life history is not known in detail. There is only one generation in a year.
The colonies of these scales may be seen covering the shoots and the fruit stalks. They suck cell sap and excrete copious amount of honeydew, which keeps dripping on the leaves and fruits, attracting ants. Sooty mould develops on honey-dew.
7. Bark Caterpillar, lndarbela Quadrinotata (Walker) (Lepidoptera: Pyralidae):
It is a notorious pest found all over India on a variety of fruit trees including loquat. The damage is conspicuous by the presence of chewed particles and excreta hanging outside the webbed galleries on the bark of tree trunks. Full account of this pest has been given under ‘Citrus’.
8. Fruit Fly, Bactrocera Dorsatis (Hendel) (Diptera: Tephritidae):
It is a polyphagous pest and attacks a number of fruits including citrus, guava, mango, loquat, apricot, fig, peach and plum. The loquat fruits attacked by the maggots do not fall down but remain on the tree. Brownish syrupy juice oozes out of the punctures. Full account of this pest has been given under ‘Mango.’