*2.3.1 International level*

Because of various types of insects that attack the cotton crop, especially from the young seedlings (leaf miner, gall formers etc.) till the crop attains maturity (various borers, weevils etc.), cotton crop receives excessive rounds of pesticides spray. This results in excessive consumption of plant protection products. Many research are being taken up towards developing holistic packages including chemical, physical, biological and IPM techniques to contain these pests. Cotton is under cultivation in 69 countries and the production had exceeded 20 million tones of lint in the recent years where the cultivable area spread on 30–35 million hectares. In spite of improvement attained through chemical control strategies, harvest losses remain very high which dwindles around 30% [37, 38]. Occurrence of varied insects in the cotton system during varied crop growth stages makes it as an experimental model crop for devising plant protection strategies to be practiced under various agronomic conditions.

Albeit very many newer molecules are synthesized and tested to contain the pests, harvest losses remained high. All the pest management strategies aims to keep the pest population below the Economic Threshold Level (ETL) which is normally attained by having a judicious mix of appropriate methodologies. Total pest management is achievable only when the pest prefers a single crop, say cotton and there are no significant alternate hosts available in the vicinity of the crop system. However, the application of IPM principles greatly depends on the concept of an intervention threshold and the limitations of many of the specific non-chemical techniques proposed but the application of IPM modules/principles have the advantage of taking into consideration the full pest complex in a cropping system [37].

Biological control by introducing beneficial arthropods has not been notably successful in all the crop based systems, which is true for cotton also. This is because of the difficulty in identifying and acclimatizing the predators/parasites, developing a bunch of beneficial organisms capable of responding effectively, the nature of the crop grown and the disrupting effects of chemical control measures

#### *High Density Planting System of Cotton in India: Status and Breeding Strategies DOI: http://dx.doi.org/10.5772/intechopen.94905*

directed against the remaining pests [39]. More benefit is to be obtained from the active conservation of the indigenous fauna of beneficial organisms. In spite of an increased general environmental awareness, the practice of using insecticides could not be resisted as pests evolve resistance to pesticides and a combinatory approach to contain the pest is the need of the hour.

Suggested strategies were adopted throughout the growing season in Australia. Primary target of reducing the pesticides consumption in cotton ecosystem was brought out by the introduction of Bt gene engineered cotton hybrids which allows the co-existence of natural enemies. However, the least affected species by the Bt toxins, the sucking pests took a prominent place in cotton based production system displacing the vegetative and fruit feeding caterpillars as key pests of Bt cotton [40]. The spatio-temporal dimension of natural population regulatory factors has led to changes in agricultural practices and production systems. In cotton, for example, production systems maintaining a permanent ground cover, are having increasing success. Many a times, farmers leave the crop in the field after harvest of bolls alone, especially for getting a second flush with the onset of rains resulting in enhanced outbreak. Intercropping and trap cropping have been favorable to the maintenance of beneficial arthropod complexes and unfavorable to the growth of pest populations. Thus for having an effective control over the pests, a changed strategy towards a total systems approach, characterized by a movement from a paradigm of pest control field-by-field, through farm-by-farm and agroecosystemby-agroecosystem, to a landscape by landscape approach is required as reported by [38].

The rich and diverse insect fauna found in cotton harbors more than one thousand species. However, very few are designated as significant potential pests. These pests damage the flowers and fruiting bodies or consumes the leaves or mine the leaves and sucks the juice of the leaves of young plants. Some of them are monophagous species, restricted to the genus *Gossypium* (*Anthonomus*, *Diaparopsis*) while oligophagous feeding on plants in the family of Malvaceae and closely related families (*Pectinophora*, *Dysdercus*, *Earias*) or polyphagous feeding behavior (*Helicoverpa*, *Heliothis*, *Cryptophlebia*, *Spodoptera*, *Helopeltis*) were also reported. The heliothine lepidopteran species complex (*Heliothis virescens*, *Helicoverpa armigera*, *Helicoverpa zea*) is considered as the most dangerous, found attacking numerous other cultivated plants which are often associated with cotton in a range of cropping systems [41]. However, as indicated earlier, the leaf hoppers and white fly are becoming a menace nowadays.
