Insect pest of cotton and their symptoms of damges

 

Insect pest

Scientific name

Symptoms of damage

Sucking pests

Jassids

Amrasca biguttula biguttula

Affected leaves curl downwards, turn yellowish, then to brownish before drying and shedding, "hopper burn" stunts young plants

Aphids

Aphis gossypii

Leaf crumpling and downward curling of leaves, sticky cotton due to deposits of honey dew on open bolls

Thrips

Thrips tabaci

Leaves of seedlings become wrinkled and distorted with white shiny patches, older crop presents rusty appearance from a distance

Whiteflies

Bemisia tabaci

Upward curling of leaves, reduced plant vigour, lint contamination with honey dew and associated fungi, transmission of leaf curl virus disease

Bollworms

Spotted & spiny bollworms

Earias vitella & E.insulana

Boremark in main shoot, dried and withered away shoot, twining of main stem due to axillary monopodia, feeding holes in flower buds and bolls blocked by excrement

American bollworm

Helicoverpa armigera

Small amount of webbing on small squares injured by young larvae, squares have a round hole near the base, larval frass and flaring of bracts on larger squares, clean feeding of internal contents of bolls, excessive shedding of buds and bolls

Pink bollworm

Pectinophora gossypiella

"Rosetted" bloom, pink larvae inside developing bolls with interloculi movement

Stainers

Red cotton bug

Dysdercus cingulatus

Feed on developing and mature seeds, stain the lint to typical yellow colour, reddish nymphs seen in aggregations around developing and open bolls

Dusky cotton bug

Oxycarenus hyalipennis

Associated with ripe seeds, all stages characterized by a powerful smell, discolour the lint f crushed

Foliage feeders

Semi - looper

Anomis flava

Causes significant loss of leaf area to young plants, larvae with looping action are seen on plant parts.

Leaf roller

Syllepte derogata

Leaves are folded and larvae are seen in groups amidst fecal materials, commonly seen on leaves at the bottom of crop canopy at low infestation levels, severe infestation defoliates the whole plant

Spodoptera leafworm

Spodoptera litura

Young larvae in groups skeletinise leaves and older larvae voraciously defoliate leaves

Grey weevil

Myllocerus subfasciatus

Marginal notching - off of leaves

Grass hopper

Crytocanthacris ranacea

Defoliation of leaves - partial or full

Root / Stem feeder

Stem weevil

Pempherulus affinis

Root damage by grubs kills young seedlings, gall like swelling seen on lower stem, wilting of seedlings