In this article we will discuss about how to control insect pests of plants.
1. Mustard Saw-Fly (Athalia Proxima):
Adult of this pest is a black fly that lays eggs singly inside the leaf tissues. From these eggs blackish caterpillars appear which attack the crop and feed on the leaves of young seedlings in the early stages. They attack leaves which curl and fall on the ground when touched.
(i) Hand picking of the caterpillar, if infestation is light and number of attacked plants is small, is the best practice for the control of larvae.
(ii) Dusting of 5% BHC or spraying Malathion @ 0.02%, 2-3 sprays of fortnightly interval will effectively control the pest.
2. Mustard Aphid (Lipahis Erysilnt):
These are the greenish white small insects attacking cauliflower and other cole crops during a cloudy weather. They suck the plant sap. The affected leaves curl up and plants wither away and die.
It may be controlled by the spray of 0.5 per cent Nicotine or Malathion.
3. Painted Bug (Bagrada Cruciferum):
It is a black and orange bug of which newly hatched nymphs are bright orange in colour. Eggs are laid on leaves or in loose soil. Both adults as well as nymphs suck the cell sap from the plants and retard their normal growth.
(i) There should not be host plants for this pest. Remove all such plants and have clean cultivation in the field.
(ii) In case of severe infestation, dust 5% BHC on the crop.
(iii) Spraying 0.25% DDT @ 560 litres per hectare is also an effective method for the control.
(iv) Spray 400 litres of fish oil resin soap her hectare to destroy the nymphs.
(v) Diamond back moth (Plutella Maculipensis).
4. Cabbage Butterfly (Pieris sp.):
The young green caterpillars feed on the surface of the leaves and skeletonise them. In case of heavy infestation, the leaves, tender shoots, flowers and fruits are completely destroyed resulting in the rugged appearance of the attacked plants.
It may be controlled by the insecticides as used for controlling the mustard saw fly.
5. Root-Knot Nematodes:
Sometimes these minute worms become serious causing check of growth and proper development of curd. Their infestation may be easily identified by the formation of galls on the roots.
Nematodes may be controlled by proper crop rotation with other crops. They may also be controlled by fumigating the soil with nematicide such as ethylene di or tribromide. About 165 to 275 litres of solution will be required for treating one hectare area.
6. Red Pumkin Beetle:
This insect attacks the pointed gourd in the establishing stage. They are elongated orange beetles which feed upon the leaves and tender shoots. Damage is caused both by the grub and adult.
This insect can be controlled by the soil application of 1% Lindane at the rate of 19-24 kg/hec or spray with Lindane (0.1%) or Sevin (0.2%).
7. Aphids:
In some seasons, aphids pose serious limitations in the successful cultivation of potatoes. These are small insects either pale yellow or dark in colour. Both nymphs and adults damage the plant by sucking the cell sap from the leaves, tender shoots and stem. The leaves of attacked plant become yellowish and curved.
If the population is very high, the affected plant may die. Besides this, the aphid secretes honey dew on leaves on which black mould develops. This interferes in the photosynthesis. The winged aphids also transmit serious viral diseases in this crop.
Spray Metasystox 25EC @ 600 mL in 1000 litres of water per hectare. If there is danger of spreading of viral diseases, it is desirable that the haulms should be cut at the time when the population of aphid is below the critical level.
8. Leaf Hoppers:
Leaf hoppers are tiny insects having slender bodies usually tapering posteriorly and rest in a position ready for jumping. When disturbed, they leap often several feet. Several species of leaf hoppers cause damage to potato crop by sucking sap from the leaves. The infested leaves turn pale; and die. Some of them are also responsible for transmitting the mycoplasma diseases.
Soil application of Phoratte 10% granules @ 15 kg per hectare in furrows at the time of planting of potatoes. If found necessary, half of this dose may be applied again at the time of earthing up. Foliar spray of Metasystox 25 EC and Rogor 30 EC @ 1.0 litre and 0.75 litres respectively in 100 litres of water per hectare is also effective.
9. Cut Worms:
The damage is caused by the caterpillars. They cut the stems or leaves of potato plants just above ground level and thus affect their growth, vigour and yield. They also feed on tubers by boring and nibbling into them and affecting their market value. In badly infested fields, as high as about 40% tubers are damaged by this pest. The full grown caterpillars are about 5 cm long. During day time they remain hiding in the soil and in the night they come out to damage the crop.
Flooding of the field reduces the activity of the caterpillar. Soil application of 5% Heptachlor or 5% Aldrin dust @ 45 kg/hec at the time of planting gives effective, control of cutworms. If the infestation is noticed after germination, Aldrin 30 EC @ 6.0 litres per hectare should be sprayed on ridges. Use of Carbafuron 5 g @ 30 kg/hec at the (time of sowing has also been found very effective.
10. Potato Tuber Moth:
Potato tuber moth is an important pest of potato in the country. Though the infestation generally starts in the field, it does not usually become serious in most places; but it causes heavy damage to the potatoes in stores in the plains. Sometimes the entire stores of potato have been reported to be lost due to attack of this pest.
The tuber moth is a small insect of dull grey colour having dark brown or black marking on the wings. The pest is active throughout the year in the plains. The caterpillar of this pest feed inside the tuber pulp. The tunnels made by the caterpillars are filled by the excreta. Such tubers generally become unfit for human consumption and seed purposes.
(i) On healthy tubers should be kept in the store.
(ii) Potatoes should be stored in cold stores. In case they are kept in ordinary stores, a sand layer of about 2.5 to 5 cm thickness should be kept below and above the heap of the potato.
11. White Grub:
The white grubs are the larvae of cockchafer beetles. They are usually present in all types of soils throughout the year in hilly areas to a depth of 10 cm to 1 cm. The grubs are fleshy white or light grey in colour with curved bodies. They damage the plant by feeding on the underground portion viz., root, stems and tubers.
The grub in early stage feed on the roots with the result the plants-dry up. Later on when tubers are developed, the grubs cut holes in the tubers. The market value of such tubers is very much reduced.
Apply Heptachlor 3% dust or Aldrin 5% dust @ 45 to 60 per hectare in soil before growing and mix it properly. Use Carbofuran 3 g, Thimlet 10 g @ 30 kg per hectare or, Temik 10 g @ 3 kg per hectare at the time of sowing.
12. Mites:
The trasonemid mite has recently assumed the status of a pest of no tat in the Deccan plateau. The mites lay eggs on the under surface of the leaves. The eggs hatch within 2-3 days. The young nymphs prepare web like structures on the lower surface of the leaves and settle down and develop under these web.
The nymph and adult mites feed by sucking the sap from leaves which roll inwards exhibiting characteristic oily spots on the upper surface while the lower surface gets sooty appearance. Subsequently the leaves become bronze coloured, wither and ultimately the whole plant dies.
13. Spotted Bollworm (Earias sp.):
The larvae of this insect which has black and brown spots bore into the shoots and fruits of bhindi and cotton plants. The growth of the plant remains stunted and the fruits are rendered unfit for the consumption.
Hollyhock and ratooned cotton, which are the host plants for bollworms, should be uprooted. The infested fruits should be removed regularly and buried deep in the soil. The chemical control measures is same as for jassids.