Earias vittella Fabricius (Spotted boll-worm)
- Class– Insecta
- Order– Lepidoptera
- Family– Cymbidae
- Genus– Earias
- Species– vittella
There are two species of spotted bollworms viz., Earias vittella and Earias insulana. Both the species are distributed in India, North Africa and Pakistan. The regions with greater rainfall are infested by E. vitella whereas, E. insulana attacks cotton crop in dry region.
Food plants :
The main host plant is cotton but they are also found feeding on lady’s finger (Bhindi), hollyhock, Deccan hemp, Shoe flower, Okra and some other malvaceous plants.
General appearance :
Earias vitella is a small moth measuring about 12 mm in length and about 25 mm across the wings. The fore-wings have a broad green band extending from the base to the apex. The forewings of E. insulana are of greenish colour and the hind wings of both the species are of white colour.
Life history :
The pest remains active and breeds throughout the year but in winter only pupae are found in debris. The pest is found in abundance during July to September. The adult moth appears in April, lays 200-400 eggs singly on bolls, bracts, shoots, flowers, top render leaves and buds. The hairy parts of the plant are most suitable for egg laying. The eggs are spherical and bluish green in colour. After an incubation period of 3-4 days in summer and 7 days in winter eggs are hatched into brownish white caterpillars provided with a dark head and prothoracic shield and measures about 13 mm in length. They start boring into the tender shoots and later on into flowers and bolls. The caterpillar passes through 6 stages of different instars and becomes full-grown in 10-15 days. The full-grown larva is brownish, measuring about 20 mm in length and provided with a patch of green, white, black and orange colours. The body is tapering towards both anterior and posterior sides. The full fed caterpillar moves out of boll and pupates in tough grey silken cocoon either on the plant or on the ground among fallen leaves. The pupal period lasts for about 15 days in summer, 21 days in autumn and 42-84 days in winter and the moth emerges out.
The whole life cycle is completed in about one month in summer. Eight overlapping generations are found in a year. The pest is carried from year to year by the roots of cotton plants and plants of bhindi left in the field with some fruits.
The infective stage is the caterpillar. The attack of this pest begins with the rain and continues all the year round except in winter. When the cotton plants are of 6-9 inches, the caterpillar bores into the top tender part of shoot which withers and droops causing 8-60% damage to crop. The caterpillars attack when the flower, bud and boll appear. A number of holes are found on the infested bolls plugged with excreta. One caterpillar can destroy many bolls in its life span of about one month. The infested bolls open prematurely and produce poor lint which fetches a lower price.
Prevention and control :
(1) In the beginning stage during June-July the attacked shoots and bolls should be collected and destroyed.
(2) At the time of attack from August onward all the infested flowers, buds and bolls infested as well as fallen should be collected and destroyed. Such plants should be shaken by dragging a rope over them so that attacked bolls may be dropped off the plants.
(3) All the alternate host plants should be destroyed from that area.
(4) After the crop is over the fruits of bhindi should not be left on plants.
(5) Resistant varieties only should be grown.
(6) Spray of carbaryl 0.1% at 15 day interval during August-September suppresses the pest population.
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