P.G. Department of Zoology Cotton Pests Pectinophora Gossypiella
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P.G. Department of Zoology B. S. N. V. PG College Charbagh, Lucknow M. Sc. Semester IV Specialization: Entomology Cotton Pests A large number of insects attack crops in various stages of growth and cause immense economic losses. Some of them are host specific while others are polyphagous and can migrate from one crop to another. Owing to their immense capabilities to destroy crops, these pests must be studied in detail and their control measures devised. The following crop pests are given in detail here. Pectinophora gossypiella (Saunders), The Pink Bollworm Systematic Position: Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Lepidoptera Family: Gelechiidae Genus: Pectinophora Species: P. gossypiella Binomial name Pectinophora gossypiella (Saunders, 1844) Synonyms: Depressaria gossypiella Hosts: It is a serious pest of cotton and also attacks hibiscus, okra, hollyhock and other malvaceous plants. Damage: In the younger crop larvae bore into tender squares and feed within resulting into drying of the terminal shoots. Later flower buds and bolls are attacked. Infested flower buds fail to open up completely due to webbing by the larva, giving the appearance of a typical rosette bloom. Larvae damage the bolls by tunneling into them, destroying the pulp and lint. Infested bolls open prematurely permitting fungal infection. Life cycle: Adult is a small moth having wingspan of 10-15 mm, dark brown, with irregular black markings on the fore wing. Hind wing silvery gray with no distinct markings. Both wings are elongated, fringed with long hairs posteriorly and the tip of hind wing is sharply pointed. Fecundity is about 150eggs/female. Eggs are flattened, pale yellow with striated surface and laid in the night on bracts, buds or flowers, singly or in small groups. Incubation period is 4-6 days. Larvae are pinkish in color with brownish head and 10 mm when full grown. Then it penetrates the lint until it reaches the seed, which also it bores and damages. There are four larval instars and total larval development takes 20-30 days depending on temperature. Larvae overwinter by curling inside cotton seeds and become active again in April. Pupation takes place either in the lint or in debris or under bracts or bark on the plant. Pupal period is 7-10 days and total life cycle is completed in 4-5 weeks. Distribution: This is a serious pest of cotton in all the cotton-growing areas of the world and particularly severe in the tropics and subtropics of Asia. Control: Field sanitation is very important. Withering shoots and infested bolls should be dislodged by passing a rope over the plants, then collected and burnt or buried. Destruction of weeds that serve as alternate hosts in the neighboring area helps to reduce population. Foliar sprays of insecticides at fortnightly interval starting with 10 week old crop kill younger and exposed larvae but the larvae which have bored into the bolls or seeds escape contact with insecticide. The following concentrations of insecticides @ of about 1000 liters per hectare have been found to be effective against this pest: Endrin 0.2%, Malathion 0.1%, Gusathion 0.05%, Carbaryl 0.15%, Cypermethrin, Permethrin or Decamethrin 0.002%. The following biological control agents help to reduce the population naturally: the egg parasite, Trichogramma acheae, the larval parasite, Bracon sp. And the pupal parasite, Eulopid sp. In addition there is also an anthocorid bug, Triphles tintilus, that feeds on the eggs of this pest. Erias vitella (Fab.) The Spotted Bollworm Earias vittella, an Asian "spotted bollworm", is a moth species in the family Nolidae. The species was first described by Johan Christian Fabricius in 1794. Most records are from Asia, Australia and certain Pacific islands. Scientific classification Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Lepidoptera Superfamily: Noctuoidea Family: Nolidae Genus: Earias Species: E. vittella Binomial name Earias vittella Fabricius, 1794 Synonyms Earias fabia (Cramer, 1781) Earias huegeli Rogenhofer, 1870 Earias vitella Sherborn, 1902 Host: Main host is cotton but also infests other malvaceous plants, namely, Okra, Hibiscus, Anthaea, Abutilon, Malvastrum etc. and is very common pest of ladyfinger. Damage: Young larvae attack growing shoots leading to drooping and withering of the top shoot. In later stages buds, flowers and bolls are also damaged. Flower buds open up prematurely causing “flared squares”. In damaged bolls pulp is eaten up and lint is stained. Life cycle: Adult has yellowish fore wings with elongated green streak in the middle. Hind wing is pale whitish. Oviposition takes place in the night, female deposits 2-3 eggs on leaf bract, flower bud or tender leaf, usually on the under surface. Fecundity is 200-400 eggs per female. Eggs are deep sky blue or greenish crowned and sculpted on the surface. Incubation period is 3-5 days. Full grown larva is about 2.0 cm long, brownish with white patches on the dorsal side of the body. There are 6 larval instars and the total larval development takes 12-18 days. Pupation takes place on the plant or rarely in the soil among fallen leaves. A boat- shaped greyish silken cocoon is constructed for pupa formation. Pupal period is 7-10 days. Distribution: Widely distributed in tropics and subtropics of the old world and Australasia. In India it is more common in Punjab and Rajasthan. Control: The following cultural practices help in reducing pest incidence, particularly when adopted on large scale on cooperative basis by farmers: After harvesting cotton plants should be cut at the ground level and refuse removed from the field. Sprouts from the harvested crop should be removed during March-April. Growth of malvaceous weeds should not be allowed in the neighbouring areas during non-cotton period. After picking of the lint, no crop should be allowed to remain in the field in the whole area. Infested portions of the plants can be handpicked and destroyed. Infested bolls can be dislodged from the plants by passing a rope over the crop. Irrigation also destroys hibernating stages of the pest. Chemical control involves timing of spray of insecticides with egg-laying or before larvae bore into the bolls. The following insecticides have been found to be effective: Parathion 0.025%, Endrin 0.02%, Carbaryl 0.1%, Endosulphan 0.05%, Sevimol and Quinalphos 0.02%. These insecticides can be sprayed at the rate of about 2.0-2.5 litre/hectare of crop. ---------------------------------------------------------------------------------------------------------------- There may be some typing or composing mistakes. The study material is compiled only for the students to enhance their understanding and learning of the subject. No copyright infringement is intended. .