Pesticides and Pest Control

Correct answer. Agrobacterium radiobacter is an effective, commercially applied, biological control agent for the prevention of crown gall disease caused by many virulent strains of Agrobacterium tumefaciens and A. rhizogenes. Trichoderma harzianum is an effective biocontrol agent against several fungal soil-borne plant pathogens.

This option is correct because Bacillus thuringiensis (or Bt) is a gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide

Bordeaux mixture is a classic copper-based fungicide composed of copper sulfate and lime. It has been widely used in agriculture since the late 19th century to control fungal diseases on various crops. Carboxin is a systemic fungicide, chloropicrin is a soil fumigant, and mercuric chloride is a mercury-based compound (now largely banned).

None of these is a commonly used pesticide.

Excessive use of pesticides pollutes the lithosphere. Lithosphere is the solid crust from the centre of the earth to the outer surface. It gets polluted due to the dumping of pesticides and herbicides. 

Pesticides are chemical substances specifically designed to control or eliminate pests that damage crops, spread disease, or cause nuisance. They include insecticides, herbicides, fungicides, and other agents targeting various pest types. The other options are too narrow - pesticides work against many types of pests, not just insects, plantlets, or weeds.

DDT is an insecticide (“insect” + “cidal” – killing). It is used to kill a variety of insects and pests, particularly mosquitoes. It should be noted here that though DDT is useful but at the same time, it is a pollutant and hence, its use must be limited. Apart from DDT, all other options given here are vaccines and hence, they cannot be used to kill mosquitoes because their function is to give immunity inside our body. BCG is a vaccine against TB; ATS is Anti Tetanus Serum and DPT is a triple vaccine against diphtheria, pertusis and typhoid.

Enzymes released by bacteria helps in breaking down biodegradable waste products.

DCMU  3-(4-chlorophenyl-1,1-dimethylurea} inhibits PS2 phase of phtosynthesis.

Heavy metal is not associated with biological magnification. Biological magnification is the increasing concentration of a chemical like toxic substance, in organism’s tissue at successively higher level in the food chain.

This is the correct option. Convolvulus is not a bio-pesticide. It is a twining plant with trumpet-shaped flowers, of which some kinds are invasive weeds and others are cultivated for their bright flowers.

Chara is a green alga, it looks like land plants due to the stem-like and  root-like morphology. They are common in fresh water and used to kill mosquito larvae.

DDT is an organochloride insecticide.

Azadirachtin:  Natural insect repellent obtained from Azadirachta indica (Neem), Rotenone: A powerful insecticide obtained from roots of Derris elliptica and Lonchocarpus spp., Pyrethrum: A contact insecticide obtained from the plant Chrasanthemum  cinerariaefolium.

Use of pesticides and  biocides can be controlled by using better technology that does not pollute the soil. Use of genetically modified crops can reduce the use of fertilisers and pesticides, but it has serious impact on food chain and food web.