In cotton, the serious sucking pest is

In cotton, the serious sucking pest is Leaf hopper.
A leafhopper is the common name for any species from the family Cicadellidae. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or trees.
Aphids that attack the cotton crop are one of the major sucking pests in cotton. These pests suck the liquid from the leaves and cotton boll of small plants and thus restrict the growth of the boll and the plant as well.
Both nymphs and adults suck the sap from the under surface of leaves, tender leaves turn yellow, leaf margins curl downwards and reddening sets in.