Microbes as Biocontrol Agents Questions in English

(C) The natural method of pest and pathogen control involving the use of viruses,bacteria,and other insects is known as biocontrol or biological control.
This method relies on natural predation and parasitism rather than synthetic chemicals.
For example,the ladybird beetle feeds on aphids,while dragonflies are effective in controlling mosquito populations.

(D) Biopesticides are pesticides of biological origin. They are classified based on the types of pests they control,such as algicides,fungicides,bactericides,herbicides (weedicides),insecticides,nematicides,and rodenticides.
Initially,they were used to protect crops from pests,but they are now equally important for destroying or controlling vectors of various animal and human pathogens.
Therefore,biopesticides can be used to control insects,weeds,and the spread of various diseases by targeting their vectors.

(B) Biological control refers to the use of biological methods for controlling plant diseases and pests. $A$ major challenge in this method is that the introduced predator or parasite does not always survive or adapt successfully when transferred to a new environment,which limits the effectiveness of the control strategy.

(D) Rice bran oil is known for its various health benefits and industrial applications. In the context of biological control and agricultural practices,it is often utilized as an insecticide. It acts by disrupting the life cycle of certain pests and is considered an eco-friendly alternative to synthetic chemical pesticides.

(D) Baculoviruses are pathogens that attack insects and other arthropods. Statement $I$ is correct.
Most of the baculoviruses used as biological control agents belong to the genus $Nucleopolyhedrovirus$. Statement $II$ is correct.
These viruses are highly species-specific and narrow-spectrum,meaning they do not harm plants,mammals,birds,fish,or other non-target insects. Statement $III$ is correct.
Baculoviruses are excellent candidates for Integrated Pest Management $(IPM)$ programmes,especially in ecologically sensitive areas where beneficial insects need to be conserved. Statement $IV$ is correct.
Since all statements are correct,the correct option is $D$.

(A) $(i)$ Ladybirds and dragonflies are useful to get rid of aphids and mosquitoes,respectively.
$(ii)$ $A$ bacterial species named $Bacillus$ $thuringiensis$ $(Bt)$ is known to kill a wide range of insects such as butterfly caterpillars. Some strains of $Bt$ can kill animal and plant parasitic nematodes,protozoans,and even cockroaches.
$(iii)$ $Trichoderma$ is a free-living saprophytic fungus that most commonly lives in root ecosystems (rhizosphere) where it acts as an effective biocontrol agent against several plant pathogens.
$(iv)$ $Rhizobium$ is a symbiotic bacterium that lives in the root nodules of legumes,not the stem,and fixes atmospheric nitrogen into organic compounds. Therefore,statement $IV$ is incorrect.

(D) Ladybird beetle is a predator that feeds on aphids.
Dragonflies are predators that feed on mosquitoes.
Therefore,the ladybird beetle and dragonflies are useful to get rid of aphids and mosquitoes respectively.

(C) The effective biocontrol agents of several plant pathogens are species of $Trichoderma$.
These are free-living fungi that are very common in root ecosystems.
They are effective biocontrol agents of several plant pathogens.

(D) Bioherbicides are biological agents used to control weeds.
$Cactoblastis cactorum$ (a moth) is used to control the prickly pear cactus.
$Phytophthora palmivora$ (a fungus) is used as a bioherbicide known as 'Devine' to control milkweed vines in citrus orchards.
Since both $Cactoblastis cactorum$ and $Phytophthora palmivora$ act as biological control agents for weeds,the correct option is $D$.

(D) Biopesticides are biological agents used to control pests. They include a wide range of organisms such as viruses (e.g.,$Baculovirus$),bacteria (e.g.,$Bacillus \ thuringiensis$),fungi (e.g.,$Trichoderma$),and protozoa. Therefore,all these groups are included in the category of biopesticides.

(A) Baculoviruses are pathogens that attack insects and other arthropods.
They belong to the genus Nucleopolyhedrovirus.
These viruses are excellent candidates for species-specific,narrow-spectrum insecticidal applications.
They have been shown to have no negative impacts on plants,mammals,birds,fish,or even on non-target insects,making them ideal for integrated pest management $(IPM)$ programs.

(C) $(i)$ Incorrect: Dried spores of $Bacillus \; thuringiensis$ are mixed with water $(H_2O)$,not kerosene,before being sprayed on vulnerable plants.
$(ii)$ Correct: $B. thuringiensis$ is specific to certain insect pests like butterfly caterpillars and does not harm other beneficial insects.
$(iii)$ Incorrect: The toxin of $B. thuringiensis$ is released in the gut (midgut) of the larvae due to the alkaline pH,not in the blood. The toxin binds to the epithelial cells of the midgut,causing lysis and death of the larvae.
$(iv)$ Correct: Genetic engineering has allowed the introduction of $B. thuringiensis$ toxin genes directly into plants (e.g.,$Bt$ cotton) to provide resistance against pests.
Therefore,statements $(i)$ and $(iii)$ are incorrect.

(D) Natural insecticides are chemical compounds derived from plants that possess insecticidal properties.
$(a)$ Rotenone is obtained from the roots of the Derris plant.
$(b)$ Pyrethrum is extracted from the flowers of Chrysanthemum cinerariifolium.
$(c)$ Nicotine is an alkaloid found in the tobacco plant ($Nicotiana$ $tabacum$).
$(d)$ Azadirachtin is a complex tetranortriterpenoid limonoid isolated from the neem tree ($Azadirachta$ $indica$).
Since all four substances are derived from natural plant sources and act as insecticides,the correct answer is $(a), (b), (c)$ and $(d)$.

(C) Organic farming is based on the principle of maintaining a balanced ecosystem.
Organic farmers believe in biodiversity and natural control mechanisms rather than the use of synthetic chemicals.
They do not believe in the extensive use of insecticides and pesticides because these chemicals are toxic and harmful to both the environment and human health.
Instead,they focus on managing pest populations through biological control methods.

(D) Sustainable agriculture focuses on maintaining soil health and reducing the use of harmful chemical pesticides.
Using spores of $Bacillus \text{ } thuringiensis$ $(Bt)$ is a key practice in sustainable agriculture because it acts as a biological control agent (biopesticide).
$Bt$ spores are specific to certain insect pests and do not harm beneficial insects or the environment, unlike synthetic chemical pesticides.
Therefore, the correct concept of sustainable agriculture among the given options is the use of $Bt$ spores for pest control.

(C) Assertion $(A)$ is correct: Baculoviruses are pathogens that attack insects and other arthropods. They are excellent candidates for species-specific,narrow-spectrum insecticidal applications.
Reason $(R)$ is incorrect: Baculoviruses are not common in root ecosystems; rather,they are typically used as biological control agents in integrated pest management $(IPM)$ programs. The description provided in the Reason refers more accurately to organisms like $Agrobacterium$ or certain mycorrhizal fungi,not Baculoviruses.

(A) $Bacillus$ $thuringiensis$ was the first bacterium to be used as a biopesticide on a commercial scale in the world. It produces insecticidal crystal proteins (Cry proteins) that are toxic to specific insect larvae, making it an effective biological control agent.

(B) To control mosquito larvae in a pond,biological control is the most effective and eco-friendly method. $Gambusia$ fish are known as mosquito-larvivorous fish because they feed on mosquito larvae. Spraying $DDT$ is harmful to the environment and other aquatic life. Regular cleaning helps,but introducing $Gambusia$ is a specific biological control measure used in public health programs.

(D) Organic farming is a method of farming that primarily aims at cultivating the land and raising crops in such a way,as to keep the soil alive and in good health by the use of organic wastes (crop,animal and farm wastes,aquatic wastes) and other biological materials along with beneficial microbes (biofertilizers) instead of chemical fertilizers and synthetic pesticides.
Chemicals such as pesticides,insecticides,and herbicides are synthetic substances used in conventional farming to control pests and weeds.
Since organic farming strictly prohibits the use of synthetic chemicals,none of the listed substances $(I, II, III)$ are used in organic farming.

(B) In biological control of pests,certain insects act as natural predators.
Ladybird beetles are well-known predators that feed on aphids,which are small sap-sucking insects that damage plants.
Dragonflies are effective predators that feed on mosquitoes,thereby helping to control their population.
Therefore,ladybird and dragonfly are useful in getting rid of aphids and mosquitoes,respectively.

(B) $Trichoderma$ species are free-living fungi that are very common in the root ecosystem. They are effective biocontrol agents of several plant pathogens. Therefore,the statement that it is a free-living bacterium is incorrect because $Trichoderma$ is a fungus,not a bacterium.

(D) $1$. $Baculoviruses$ are pathogens that attack insects and other arthropods.
$2$. They belong to the genus $Nucleopolyhedrovirus$.
$3$. These viruses are excellent candidates for species-specific,narrow-spectrum insecticidal applications.
$4$. They have been shown to have no negative impacts on plants,mammals,birds,fish,or even on non-target insects,which is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management $(IPM)$ programme.
$5$. Therefore,all the given statements are correct.

(D) Biological control is a method of controlling pests in agriculture that relies on natural predation rather than introduced chemicals.
Predators are organisms that hunt and kill their prey.
In agricultural ecosystems,specific predators (or parasitoids) are introduced to control the population of pests that damage crops.
For example,the ladybird beetle is used to control aphids,and dragonflies are used to control mosquitoes.
Therefore,biological control methods are primarily based on the principle of predation.

(B) $Trichoderma$ is a fungus that acts as a biocontrol agent against several plant pathogens.
$Baculoviruses$ are pathogens that attack insects and other arthropods,and they are excellent candidates for species-specific,narrow-spectrum insecticidal applications.
Both are widely used in integrated pest management programs as biological control agents to reduce the reliance on chemical pesticides.
Therefore,they are used as biocontrol agents.

(A) Biocontrol agents are organisms used to control pests and diseases in agriculture.
$1$. $Ladybird$ (beetle) is used to control aphids.
$2$. $Trichoderma$ (fungus) is used to control several plant pathogens.
$3$. $Nucleopolyhedrovirus$ (baculovirus) is used as a narrow-spectrum insecticidal agent.
Therefore,the correct group is $Ladybird$,$Trichoderma$,and $Nucleopolyhedrovirus$.

(D) $IPM$ (Integrated Pest Management) is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques.
$1$. It encourages the use of organic farming practices to maintain soil health and plant vigor.
$2$. It emphasizes the use of biocontrol agents (natural predators,parasites,or pathogens) to manage pest populations.
$3$. It promotes the use of selective,narrow-spectrum insecticidal viruses (like Baculoviruses) that target specific pests without harming beneficial insects or the environment.
Therefore,all the mentioned options are integral components of $IPM$.

(A) $Nosema$ $locustae$ is a microsporidian protozoan that acts as a biological control agent. It is specifically used to control grasshoppers and crickets by infecting their gut and causing disease,which eventually leads to the death of the pest. This is an example of using biological methods to manage agricultural pests without relying solely on chemical pesticides.

(C) bioherbicide is a biological agent used to control weeds.
$Pseudomonas$ $spp$,$Xanthomonas$ $spp$,and $Agrobacterium$ $spp$ are bacteria used as bioherbicides.
$Fusarium$ $spp$ is a fungus,and therefore it is classified as a mycoherbicide,not a bacterial bioherbicide.

(B) Biological control agents are used to manage weeds.
$Alternaria \ crassa$ is a specific fungal pathogen used as a bioherbicide to control the growth of water hyacinth $(Eichhornia \ crassipes)$.

$Phytophthora \ palmivora$	Controls milkweed in orchards
$Xanthomonas \ spp$	Attacks several weeds
$Fusarium \ spp$	Controls most of the weeds

(C) The correct matches are as follows:
$a$. $Bacillus$ $papillae$ is a pathogen that infects $Cabbage$ $worms$ $(ii)$.
$b$. $Beauveria$ $bassiana$ is an entomopathogenic fungus used to control $Aphids$ $(iii)$.
$c$. $Nosema$ $locustae$ is a microsporidian parasite used as a biological control agent against $Grasshoppers$ $(iv)$.
$d$. $Nucleopolyhedrovirus$ $(NPV)$ is a baculovirus used to control $Gypsy$ $moths$ $(i)$.
Therefore,the correct matching is $(a) - (ii), (b) - (iii), (c) - (iv), (d) - (i)$.

(C) herbicide is a chemical or biological agent used to kill or inhibit the growth of unwanted plants (weeds).
$Pseudomonas$ $sp.$,$Xanthomonas$ $sp.$,and $Agrobacterium$ $sp.$ are all types of bacteria.
$Fusarium$ $sp.$ is a genus of filamentous fungi,not bacteria.
Therefore,$Fusarium$ $sp.$ is not a bacterial herbicide.

(B) mycoherbicide is a biological herbicide based on fungi.
$Phytophthora palmivora$, $Alternaria crassa$, and $Fusarium sp.$ are all fungal pathogens used as mycoherbicides.
$Xanthomonas sp.$ is a genus of bacteria, not a fungus; therefore, it is not a mycoherbicide.

(B) $Trichoderma$ is a genus of fungi that is present in all soils,where they are the most prevalent culturable fungi. It is widely used as a biological control agent against various plant pathogens.

(B) $Gambusia$ fish are known as larvivorous fish. They are introduced into water bodies to control the population of mosquitoes because they feed on mosquito larvae and eggs,thereby helping to prevent diseases like malaria and dengue.

(A) The biocontrol agents known as $Baculoviruses$ are pathogens that attack insects and other arthropods. These viruses are excellent candidates for species-specific,narrow-spectrum insecticidal applications. They are especially desirable when beneficial insects need to be conserved in an integrated pest management $(IPM)$ program.

(C) Baculo viruses are pathogens that attack insects and other arthropods. The majority of baculo viruses used as biological control agents are in the genus $Nucleopolyhedrovirus$. These viruses are excellent candidates for species-specific,narrow-spectrum insecticidal applications and have been shown to have no negative impacts on plants,mammals,birds,fish,or even on non-target insects. Therefore,the correct option is $C$.

(B) $Trichoderma$ is a genus of fungi that are present in all soils,where they are the most prevalent culturable fungi. They are used as biocontrol agents against several plant pathogens.

(B) $Trichoderma$ species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens. They act as antagonists to various soil-borne plant pathogens,thereby helping in the treatment and prevention of plant diseases. Therefore,option $B$ is the correct answer.

(C) The correct answer is $C$. Ladybirds (beetles with red and black markings) are well-known biological control agents that feed on aphids. They are used in agriculture to naturally control aphid populations,which are pests that damage crops by sucking plant sap.

(A) Baculoviruses are pathogens that attack insects and other arthropods. The majority of baculoviruses used as biological control agents are in the genus $Nucleopolyhedrovirus$. These viruses are excellent candidates for species-specific,narrow-spectrum insecticidal applications. They have been shown to have no negative impacts on plants,mammals,birds,fish,or even non-target insects,making them ideal for integrated pest management $(IPM)$ programs.

(B) Biocontrol agents are organisms used to control pests and diseases in an eco-friendly manner.
Option $B$ is incorrect because biocontrol agents are specifically used to reduce the reliance on harmful synthetic pesticides and chemicals.
They are beneficial for the environment as they do not harm non-target organisms and are highly effective in ecologically sensitive areas.

(B) Biological control agents are organisms that control pests and diseases.
$1$. $Trichoderma$ is a fungus used against plant pathogens.
$2$. $Baculoviruses$ (genus $Nucleopolyhedrovirus$) are effective narrow-spectrum insecticides.
$3$. $Bacillus$ $thuringiensis$ is a bacterium whose crystal toxins are used as pesticides.
Other options contain biofertilizers (like $Azospirillum$,$Anabaena$,$Azotobacter$,$Glomus$,$Rhizobium$).