Question

Name the pest that destroys the cotton bolls. Explain the role of Bacillus thuringiensis in protecting the cotton crop against the pest to increase the yield.

Answer 1

A pest is defined as any variety of plants or animals that is harmful to humans or portrays a great cause for concern. This term is particularly used for those creatures that damage crops and human livestock. A pest belonging to the family of moths destroys cotton bolls. It is also a major pest of other cultivable crops.

Complete answer:
The pest that destroys the cotton bolls is Cotton bollworm. It is also known by different names such as Corn earworm or Old world Bollworm. Another pest named Corn Borer is equally harmful to cotton bolls.

Important points regarding cotton bollworm-
• The scientific name for this month is Helicoverpa armigera.
• The larvae of this moth are polyphagous (feeds on agriculturally important crops).
• The female moth lays around a hundred eggs and the larva are produced within three days.
• It is cosmopolitan (worldwide) in distribution.
• It not only feeds on Cotton but other plant species are also destroyed such as Cotton, Tobacco, Maize, ChickPeas, etc.
• When cotton is infected with this pest, the cotton balls will fall off or if not then there will be less production of lint and the result obtained will be of inferior quality.
• This played a major effect on the yield as the yield produced was low.
• Before, other methods were used such as the use of pesticides (NOCTOVI adulticide attract and kill formulation), weeding, ploughing, biological control (Trichogramma species), etc.

These methods were not purely satisfactory. So, to increase the yield, the use of biotechnology proved helpful. A new strain of Cotton known as BT cotton was introduced. It included the bacteria, Bacillus thuringiensis. The importance of this bacteria inside cotton is that it produces an inactive protein called crystal protein which is obtained from the cry gene. But once the insect ingests the inactive toxin (crystal protein) it is converted into an active form of toxin due to the alkaline pH of the alimentary canal of the insect as it activates only in the presence of alkaline pH.

It then binds to the surface of the epithelial cell and creates pores that cause the cell to swell and eventually leading to the death of that organism.

Note: Important points to remember-
The bacteria is not affected with crystal protein because there was no presence of alkaline pH in bacteria but once it got transferred to the pest, it got activated because of the desirable conditions and hence leading to the death of organisms.
So, the advent of BT cotton was economically important for higher-yielding varieties of Cotton.