Microbes as Biocontrol Agents Questions in English

(D) Third generation pesticides refer to insect hormone analogues,such as juvenile hormone mimics.
These substances interfere with the normal development and metamorphosis of insects,preventing them from reaching the adult stage.
Unlike first-generation (inorganic) and second-generation (synthetic organic) pesticides,these are highly specific and generally considered more environmentally friendly.

(A) $IPM$ (Integrated Pest Management) is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control,habitat manipulation,modification of cultural practices,and use of resistant varieties.
Biological control is a key component of $IPM$,where natural predators,parasites,or pathogens are used to control pest populations,thereby reducing the reliance on chemical pesticides.

(B) The correct answer is $B$. Biological control is considered the latest and most sustainable trend in plant disease management. It involves the use of living organisms,such as predators,parasites,or pathogens,to control pests and diseases,thereby reducing the reliance on harmful chemical pesticides.

(C) The classification of pesticides is based on their development and mode of action.
First-generation pesticides include inorganic compounds like arsenic and sulfur.
Second-generation pesticides include synthetic organic compounds like $DDT$ and organophosphates.
Third-generation pesticides are based on insect growth regulators,specifically juvenile hormone analogues (JHAs),which disrupt the development of insects by mimicking their natural hormones.
Therefore,the correct answer is $C$.

(B) $IPM$ stands for Integrated Pest Management.
It is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control,habitat manipulation,modification of cultural practices,and use of resistant varieties.
In the context of agriculture,it aims to minimize the use of chemical pesticides to protect the environment and human health.

(D) The neem tree $(Azadirachta \, indica)$ is well-known for its medicinal and insecticidal properties.
$Azadirachtin$ is the primary active compound extracted from neem seeds, which acts as a powerful natural insecticide and insect repellent.
It disrupts the growth and development of insects, making it an effective bio-pesticide.

(D) The full name of $BHC$ is Benzene hexachloride,which is also known as Hexachlorocyclohexane $[C_6H_6Cl_6]$.
It is a well-known organochlorine chemical compound used as an insecticide.
Therefore,both $(a)$ and $(b)$ are correct names for the same chemical structure.

(A) $Rotenone$ is a natural insecticide that was the first to be used by humans for pest control.

(D) Rotenone is a naturally occurring compound found in the roots and stems of several tropical plants,such as those in the genus $Derris$. It acts as a broad-spectrum insecticide and piscicide. It works by inhibiting the mitochondrial electron transport chain,specifically targeting complex $I$,which prevents the production of $ATP$ in insects and fish,leading to their death. Therefore,it is classified as a natural insecticide.

(B) The correct answer is $B$.
Natural insecticides,specifically Azadirachtin,are obtained from the seeds of the $Azadirachta$ $indica$ (Neem or margosa) plant.
Azadirachtin acts as an antifeedant and growth disruptor for many insect pests,making it an effective and eco-friendly biopesticide.

(D) 'Sporeine' is a commercial preparation of the bacterium $Bacillus \text{ } thuringiensis$ $(Bt)$.
It contains the spores and the toxic protein crystals produced by the bacterium.
When these spores are ingested by insect larvae, the toxin is released in the gut, which kills the larvae.
Therefore, it is used as a biological control agent against insect pests, making it an insecticide.

(C) The first bioinsecticide developed on a commercial scale was $Sporeine$,which is based on the bacterium $Bacillus$ $thuringiensis$ $(Bt)$.
It contains insecticidal crystal proteins (Cry proteins) that are toxic to specific insect larvae.
$Morphine$ and $Quinine$ are alkaloids used as medicines,and $Phytophthora$ $palmivora$ is a fungal pathogen used as a mycoherbicide.

(C) $Gambusia$ is a larvivorous fish that feeds on mosquito larvae. By introducing $Gambusia$ into water bodies like ponds and tanks,the population of mosquito larvae is significantly reduced,which helps in the biological control of mosquito-borne diseases like malaria and dengue.

(D) Thurioside (often referred to as $Bt$ toxin) is a proteinaceous insecticidal toxin produced by the bacterium $Bacillus$ $thuringiensis$.
This bacterium produces crystal proteins during a particular phase of its growth.
These crystals contain a toxic insecticidal protein.
Therefore,it is of bacterial origin.

(C) The natural insecticide $Rotenone$ is obtained from the roots of the plant $Derris$ $elliptica$.
It is a broad-spectrum insecticide and piscicide used in various agricultural and horticultural applications.

(D) Biological control involves the use of natural predators,parasites,or pathogens to manage pest populations. Unlike chemical pesticides,which are often toxic,polluting,and require repeated application,biological control agents can establish themselves in the environment and reproduce,making them self-perpetuating. This method is sustainable and environmentally friendly.

(A) The sterile insect technique $(SIT)$ involves the mass rearing and sterilization of male insects using radiation.
When these sterile males are released into the wild,they mate with wild females.
Since the males are sterile,no offspring are produced,leading to a decline in the pest population over successive generations.
The most successful application of this method was the eradication of the screw-worm fly ($Cochliomyia$ $hominivorax$) in various regions.

(D) Ladybugs (beetles with red and black markings) are well-known predators that feed on aphids. They are used as biological control agents in agriculture to manage aphid populations,which are harmful pests to many crops.

(A) $Sporeine$ is the first commercial bioinsecticide developed in $Germany$ using the bacterium $Bacillus$ $thuringiensis$ $(Bt)$.
It contains the spores and crystalline toxins of the bacterium,which are effective against specific insect pests.

(C) The correct answer is $C$.
Thurioside (often referred to as $Bt$ toxin) is a proteinaceous crystal toxin produced by the bacterium $Bacillus$ $thuringiensis$.
This toxin is highly specific and is toxic to several insect larvae,making it useful in biological pest control.

(C) is the correct answer.
Biological control refers to the method of controlling pests or harmful organisms by using their natural predators,parasites,or pathogens instead of chemical pesticides.
This process involves manipulating the biology or physiology of the target organism to stop its reproduction or directly destroying it using another living organism.

(C) The fish $Gambusia$ is widely known as the 'mosquito fish'.
It is a small freshwater fish that feeds voraciously on mosquito larvae.
Because of this biological control property,it is introduced into ponds and water bodies to control the spread of mosquito-borne diseases like malaria and dengue.

(C) Gambusia is a type of freshwater fish commonly known as the 'mosquito fish'.
It is introduced into ponds and water bodies to control the population of mosquitoes.
This is because Gambusia feeds on the larvae of mosquitoes,thereby preventing the spread of diseases like malaria and dengue.
Therefore,it is a biological control agent for mosquitoes.

(B) The first commercially developed insecticide was $Pyrethrin$. $Pyrethrin$ is a natural organic compound derived from the flowers of the $Chrysanthemum$ plant. It acts as a potent contact insecticide that disrupts the nervous system of insects. While other options like $Morphine$ are alkaloids used for medicinal purposes,and $Rotenone$ is also a natural pesticide,$Pyrethrin$ holds the historical distinction of being the first to be widely commercialized.

(A) Thuringioside is a biological insecticide derived from the bacterium $Bacillus \ thuringiensis$. It is used to control various insect pests in agriculture by producing toxic proteins that target specific insect larvae.

(B) Cyclosporin $A$ is a bioactive molecule produced by the fungus $Trichoderma$ $polysporum$.
It is widely used as an immunosuppressive agent in organ transplant patients.
It acts by inhibiting the activation of $T$-cells,thereby preventing the immune system from rejecting the transplanted organ.
Therefore,it is not used to control pathogens or pests directly,but the question refers to the source organism $Trichoderma$ $polysporum$ which is a fungus. However,in the context of biological control,$Trichoderma$ species are free-living fungi that are very common in the root ecosystems and are effective biocontrol agents of several plant pathogens (fungi).

(A) The ladybird beetle is a well-known predator used in biological control of pests.
It is specifically used to control populations of aphids,which are small sap-sucking insects that damage plants.
By feeding on aphids,the ladybird beetle helps in reducing the need for chemical insecticides in agriculture.

(A) The prickly pear cactus $(Opuntia)$ was introduced into Australia in the early $19th$ century,where it spread rapidly and became a major weed. To control its spread,the moth $Cactoblastis$ $cactorum$ (a biological control agent) was introduced. This moth feeds on the cactus,effectively reducing its population and controlling its spread.

(C) The sterile insect technique $(SIT)$ is a method of biological pest control. It involves releasing large numbers of sterile insects into the wild. When these sterile insects mate with wild fertile insects,they produce no offspring,leading to a decline in the population of the pest. The screwworm fly ($Cochliomyia$ $hominivorax$) was the first major success story of this technique,where it was effectively eradicated from large areas of North America.

(A) The correct answer is $A$. $Gliocladium virens$ is a well-known fungus used as a biological control agent. It is highly effective in suppressing various soil-borne plant pathogens,such as $Rhizoctonia$ and $Pythium$ species,by producing antifungal compounds and through mycoparasitism. While other options like $Pseudomonas$ species also have biocontrol properties,$Gliocladium virens$ is specifically recognized for its efficacy in agricultural applications.

(D) Integrated Pest Management $(IPM)$ is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques.
These techniques include biological control (using natural predators or parasites),mechanical control (physical barriers or traps),and the judicious,timely use of chemical pesticides only when necessary to minimize risks to human health and the environment.
Therefore,all the mentioned options are integral components of an $IPM$ program.

(A) The Bordeaux mixture was the first inorganic pesticide developed on a commercial scale. It was discovered by Pierre-Marie-Alexis Millardet in $1882$ in France. It is a mixture of copper sulfate $(CuSO_4)$,lime $(Ca(OH)_2)$,and water. It was primarily used to control downy mildew on grapevines. $D.D.T$ and $2,4-D$ are organic pesticides/herbicides,not inorganic.

(D) The correct answer is $Bacillus \ thuringiensis$ $(Bt)$.
$Bacillus \ thuringiensis$ is a soil-dwelling bacterium that produces protein crystals during sporulation.
These crystals contain a toxic insecticidal protein known as the $Bt$ toxin.
This bacterium is widely used as a biological control agent (biopesticide) to control butterfly caterpillars and other insect pests in agriculture.

(A) The correct matches are as follows:
$(a)$ Rotenone is a natural insecticide derived from the roots of the plant $Derris$ $elliptica$.
$(b)$ Nimbin is a bioactive compound extracted from the neem tree, $Azadirachta$ $indica$.
$(c)$ Pyrethrum is an insecticide obtained from the flower heads of $Chrysanthemum$ $cinerariifolium$.
$(d)$ Thurioside (or Bt toxin) is a biopesticide produced by the bacterium $Bacillus$ $thuringiensis$.
Therefore, the correct matching is $a-1, b-2, c-3, d-4$.

(C) Pyrethroids are a class of organic compounds originally derived from the flowers of the $Chrysanthemum$ plant. These compounds act as natural insecticides,effectively targeting the nervous system of insects. They represent the largest and most significant group of plant-derived insecticides used in agriculture and pest control.

(D) $Bacillus$ $thuringiensis$ $(Bt)$ is a bacterium that produces a specific insecticidal protein.
This protein is toxic to certain insect larvae.
It is widely used as a biological control agent to control various pests,including lepidopterans (tobacco budworm,armyworm),coleopterans (beetles),and dipterans (flies and mosquitoes).
Therefore,it is effective against moths,flies,and mosquitoes.

(C) Bio-pesticides is a broad term that refers to the use of biological organisms or their derivatives to control pests.
This category encompasses various agents,including bio-insecticides (which target insects) and bio-herbicides (which target weeds).
Therefore,bio-pesticides include both bio-insecticides and bio-herbicides.

(B) $Trichoderma$ $harzianum$ is a free-living fungus that is very common in the root ecosystems. It is an effective biocontrol agent used against several soil-borne plant pathogens. It acts by producing enzymes and secondary metabolites that inhibit the growth of harmful fungi,thereby protecting the plants.

(B) The method of using natural predators or parasites to control pests is known as $Biological \ control$. This approach relies on natural predation rather than introduced chemicals, making it an eco-friendly method of pest management in agriculture.

(D) Natural insecticides are derived from various plant sources.
$1$. $Azadirachta indica$ (Neem) contains azadirachtin,which acts as a potent natural insecticide.
$2$. $Derris elliptica$ contains rotenone,which is a well-known natural insecticide.
$3$. $Chrysanthemum cinerariifolium$ is the source of pyrethrins,which are widely used as natural insecticides.
Therefore,all the mentioned plants are sources of natural insecticides.

(B) The correct answer is $B$.
$Trichoderma$ species are free-living fungi that are very common in the root ecosystems.
They are effective biocontrol agents of several plant pathogens.
$Baculoviruses$ (including $Nucleopolyhedrovirus$) are pathogens that attack insects and other arthropods,not plant pathogens.
$Ladybird$ beetles and dragonflies are used to control aphids and mosquitoes,respectively.

(B) $IPM$ stands for Integrated Pest Management.
It is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control,habitat manipulation,modification of cultural practices,and use of resistant varieties.
Among the given options,biological control is a fundamental component of $IPM$.

(C) Biological control refers to the use of biological methods for controlling plant diseases and pests.
$Trichoderma$ species are free-living fungi that are very common in the root ecosystems.
They are effective biocontrol agents of several plant pathogens.
Ladybird beetles are used to control aphids,but they are insects,not microbes.
$Bt-$ cotton is a genetically modified crop,not a direct biocontrol agent.
Therefore,the correct example of using microbes for biological control is $Trichoderma$.

(A) The genetically engineered microorganism used for the bioremediation of oil spills is $Pseudomonas$ $putida$.
This bacterium was developed by Dr. Ananda Mohan Chakrabarty and is capable of breaking down hydrocarbons found in crude oil.
Therefore,the correct option is $A$.

(C) $Trichoderma$ species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens. $Trichoderma$ acts as a parasite on various fungal pathogens,thereby protecting plants from soil-borne diseases.

(C) $Bacillus$ $thuringiensis$ $(Bt)$ is a soil-dwelling bacterium that produces insecticidal crystal proteins (Cry proteins) during sporulation.
These proteins are toxic to specific insect larvae,such as those of lepidopterans,coleopterans,and dipterans.
Because of this property,$Bt$ is widely used in modern biotechnology as a bio-insecticide to protect crops from pests without the need for synthetic chemical pesticides.
This application is the basis for the development of $Bt$ crops,such as $Bt$ cotton.

(A) Gambusia is a genus of fish,commonly known as mosquito fish.
These fish are widely used in biological control programs to manage mosquito populations because they feed on mosquito larvae in water bodies.
By consuming the larvae,they prevent the mosquitoes from reaching the adult stage,thereby reducing the spread of diseases like malaria and dengue.

(A) The correct matches are as follows:
$(a)$ Rotenone is a natural insecticide derived from the roots of the plant $Derris \text{ } elliptica$.
$(b)$ Nimbin is a bioactive compound extracted from the Neem tree, $Azadirachta \text{ } indica$.
$(c)$ Pyrethrum is an insecticide obtained from the flower heads of $Chrysanthemum \text{ } cinerariifolium$.
$(d)$ Thurioside (or Bt toxin) is produced by the bacterium $Bacillus \text{ } thuringiensis$.
Therefore, the correct sequence is $a-1, b-2, c-3, d-4$.

(D) The correct answer is $D$. $Pseudomonas$ $cepacia$ is a well-known plant growth-promoting rhizobacterium that acts as an effective biocontrol agent against various soil-borne plant pathogens. It suppresses the growth of harmful fungi and bacteria in the rhizosphere,thereby protecting the plant roots.

(A) Ladybird is a beetle with red and black markings. It is a biological control agent used to control aphids. Aphids are small sap-sucking insects that damage plants. By feeding on aphids,ladybirds help in protecting crops and gardens without the use of harmful chemical pesticides.