P.G. Department of Zoology B. S. N. V. PG College Charbagh, Lucknow

M. Sc. Semester IV Specialization: Entomology

Cotton Pest Introduction

Cotton, ( spp.) an important commercial crop (cash crop) for fibre, fuel and edible oil, playing an important role in Indian economy. Cotton in India also plays an important role in socio-economic well being of the people, but productivity is very low in comparison to other countries. Several biotic and abiotic factors contribute to low cotton yield, of which -pests are the major component. Application of is costly and led to development of resistance and adverse effects on the non-target organisms. One approach to combat this problem and reduce use could be through host plant resistance, to develop lines resistant to spotted bollworm, a thorough knowledge of the resistance mechanisms on different cotton genotypes is also needed. Insecticide resistance to representatives of commonly used insecticide groups (pyrethroids - cypermethrin; organophosphates - chlorpyriphos; cyclodienes - endosulfan) was determined in five major insect pests of cotton from the main cotton growing regions of India. The overall resistance of the pink bollworm Pectinophora gossypiella (Saunders) to pyrethroids was low. However, high resistance levels of 23–57 fold to endosulfan were recorded in some areas of Central India. Resistance to chlorpyriphos & endosulfan was high in the strain from North India . Insecticide resistance in Earias vittella (Fab.) was low to moderate from North India strains. The implications of resistance for cotton pest management in India must be discussed.

A large number of 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.

Pests and weeds The cotton industry relies heavily on chemicals, such as fertilizers, insecticides and herbicides, although a very small number of farmers are moving toward an organic model of production. Under most definitions, organic products do not use transgenic Bt cotton which contains a bacterial gene that codes for a plant-produced protein that is toxic to a number of pests especially the bollworms. For most producers, Bt cotton has allowed a substantial reduction in the use of synthetic insecticides, although in the long term resistance may become problematic.

Global pest problems Significant global pests of cotton include various species of bollworm, such as Pectinophora gossypiella. Sucking pests include cotton stainers, Dysdercus suturellus; the chili thrips, Scirtothrips dorsalis; the cotton seed bug, Oxycarenus hyalinipennis. Defoliators include the fall armyworm, Spodoptera frugiperda.

Dysdercus (cotton stainer) Scientific classification/ Kingdom Animalia Subkingdom Bilateria Infrakingdom Protostomia Superphylum Ecdysozoa Phylum Arthropoda Subphylum Hexapoda Class Insecta Subclass Dicondylia Subclass Pterygota Infraclass Neoptera Order Suborder Heteroptera Infraorder Pentatomomorpha Superfamily Pyrrhocoroidea Family Genus Dysdercus Species Dysdercus suturellus Binomial name Dysdercus suturellus (Herrich-Schaeffer, 1842)

Dysdercus suturellus is a species of true bug in the family Pyrrhocoridae, commonly known as a cotton stainer. The adult insect is slender, about 1 to 1.5 cm (0.4 to 0.6 in) long, with a red thorax and dark brown wings marked with a yellow cross. It is native to the southeast of the United States, Jamaica and Puerto Rico. It is a pest of cotton crops and other plants, the adults and older nymphs feeding on the emerging bolls and the ripening seeds.

Description The adult Dysdercus suturellus is about 1 to 1.5 cm (0.4 to 0.6 in) long. It has a red head with black antennae, the first segment of which are longer than the second. The thorax has a white pronotal collar and is otherwise mostly red. The sternites of the abdomen are red, bordered with white posteriorly. The corium, the leathery base of the wings, is dark brown margined with cream, giving the insect a large cross-shaped pattern.

Distribution and hosts Dysdercus suturellus is native to the south eastern most part of the United States, Jamaica and Puerto Rico. It is a pest of cotton crops and its distribution has been linked to the area of cotton under cultivation. Other host plants include tangerines, , papaya, oleander, roselle ( sabdariffa), rose of Sharon (), Turk's cap mallow, teaweed (Sida sp.), Caesarweed (Urena lobata), Spanish needles (Bidens pilosa), Portia tree (Thespesia populnea), rose, eggplant, black nightshade (Solanum nigrum) and guava. The host plants are all in the families , Sterculiaceae, Bombacaceae and Tiliaceae.

Life cycle Dysdercus suturellus is a true bug and does not undergo metamorphosis. The eggs are pale yellow and are laid singly or in small groups in sand, leaf or plant debris, and hatch in about a week. The nymphs pass through five instars (developmental stages) over the course of three to five weeks. The first instar lives underground after which the nymph climbs the host plant. The nymphs are largely red but in the fourth and fifth instars, the dark wingpads are apparent as they enlarge, and the abdominal segments develop pale margins and become more obvious. There are several generations each year.

Figure: Adults and nymphs of the cotton stainer, Dysdercus suturellus Biology

Figure. Nymphs of the cotton stainer, Dysdercus suturellus

Figure. Close up of a nymph of the cotton stainer, Dysdercus suturellus

The adults and late stage nymphs feed on the protein-rich seeds of their host plants. As these become available at different times of year, the winged adults migrate between different plant species. The adults have also been observed predating the larvae of the cotton leafworm (Alabama argillacea) and the larvae and pupae of the yellow scallop ( erosa). They also feed on the nectar of many species of flowers and on various fruits, including citrus. When these insects feed on cotton bolls, the young bolls fail to mature, and the lint becomes stained which reduces the value of the crop. When they feed on citrus, they plunge their rostrum (beak-like mouthparts) deep into the fruit which may then fall a few hours later, or decay internally over the next few days.

Figure. Dorsal view of adult Dysdercus suturellus

Figure. Lateral view of adult cotton stainer, Dysdercus suturellus

Figure. Mating adult cotton stainers, Dysdercus suturellus

------

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.