Part 5: Microbes as Biocontrol Agents (25 MCQs)
Part 5: Microbes as Biocontrol Agents – natural predators, biopesticides, insecticidal microbes (25 MCQs)
Q101. Biocontrol refers to:
a) Killing pests with chemicals
b) Use of natural predators and microbes to control pests
c) Removing weeds by burning
d) Genetic engineering of crops
Answer: b
- b) Correct: Biocontrol = use of living organisms like microbes or predators against pests.
Q102. Which is a classic example of microbial biocontrol agent?
a) Bacillus thuringiensis
b) Lactobacillus
c) Streptococcus
d) Rhizobium
Answer: a
- a) Correct: Bacillus thuringiensis (Bt) → insecticidal protein.
Q103. Bt toxin is effective against:
a) Bacteria
b) Insects like caterpillars, beetles, mosquitoes
c) Viruses
d) Fungi
Answer: b
- b) Correct: Bt toxin → kills caterpillars, beetles, mosquitoes.
Q104. The Bt toxin gene has been introduced into crops like:
a) Rice
b) Cotton
c) Wheat
d) Mustard
Answer: b
- b) Correct: Bt cotton → resistant to bollworm.
Q105. Bt toxin kills insects by:
a) Blocking nerve signals
b) Forming pores in midgut lining of insects
c) Causing paralysis of wings
d) Destroying insect DNA
Answer: b
- b) Correct: Bt toxin → pores in insect gut → cell lysis → death.
Q106. Trichoderma species are widely used as:
a) Biocontrol agents against plant pathogens
b) Nitrogen-fixers
c) Biogas producers
d) Probiotics
Answer: a
- a) Correct: Trichoderma → free-living fungi, suppress plant pathogens.
Q107. Which virus is used as biocontrol agent for insects?
a) Baculovirus (Nucleopolyhedrovirus)
b) Retrovirus
c) HIV
d) Adenovirus
Answer: a
- a) Correct: Baculoviruses (NPV) → highly host-specific, used against insect pests.
Q108. Nucleopolyhedrovirus (NPV) is useful because:
a) It infects humans
b) It controls insect pests without harming other organisms
c) It produces antibiotics
d) It kills weeds
Answer: b
- b) Correct: NPVs = highly selective, eco-friendly biocontrol agents.
Q109. Which of the following is NOT a biocontrol agent?
a) Ladybird beetle
b) Dragonfly
c) Bacillus thuringiensis
d) DDT
Answer: d
- d) Correct: DDT = chemical pesticide, not biocontrol.
Q110. Ladybird beetles are useful in controlling:
a) Mosquito larvae
b) Aphids
c) Bollworms
d) Caterpillars
Answer: b
- b) Correct: Ladybird beetles feed on aphids (biocontrol).
Q111. Dragonflies are useful in controlling:
a) Houseflies
b) Aphids
c) Mosquitoes
d) Caterpillars
Answer: c
- c) Correct: Dragonflies eat mosquito larvae/adults.
Q112. Biocontrol is considered better than chemical control because:
a) It is environment-friendly
b) It is highly specific
c) It does not create resistance
d) All of the above
Answer: d
- d) Correct: Biocontrol = safe, specific, sustainable.
Q113. Which fungal biocontrol agent suppresses soil-borne pathogens?
a) Penicillium
b) Trichoderma
c) Rhizopus
d) Saccharomyces
Answer: b
- b) Correct: Trichoderma suppresses fungal plant pathogens.
Q114. Example of microbial insecticide used in mosquito control is:
a) Trichoderma
b) Bacillus thuringiensis
c) Streptomyces
d) Acetobacter
Answer: b
- b) Correct: Bt formulations sprayed to kill mosquito larvae.
Q115. Which is NOT an advantage of biocontrol?
a) Eco-friendly
b) Specificity
c) Resistance development in pests
d) Sustainable method
Answer: c
- c) Correct: Resistance develops mostly against chemical pesticides, not biocontrol.
Q116. Which is the principle behind integrated pest management (IPM)?
a) Use of chemicals only
b) Combination of biocontrol + minimal chemical control
c) Vaccination
d) Burning of pests
Answer: b
- b) Correct: IPM combines biocontrol with limited safe pesticide use.
Q117. Which microorganism acts as mycoparasite against other fungi?
a) Lactobacillus
b) Trichoderma
c) Rhizobium
d) Azotobacter
Answer: b
- b) Correct: Trichoderma parasitizes pathogenic fungi.
Q118. Biopesticides are defined as:
a) Synthetic chemicals
b) Biological agents like microbes, plants, predators to control pests
c) Antibiotics
d) Hormones
Answer: b
- b) Correct: Biopesticides = living organisms or their products controlling pests.
Q119. An example of viral biopesticide is:
a) NPV (Baculovirus)
b) HIV
c) Adenovirus
d) Poliovirus
Answer: a
- a) Correct: NPVs are used as biopesticides.
Q120. Which of the following is applied as a spray to control insects?
a) Bt spores/crystals
b) Trichoderma spores
c) Azotobacter culture
d) Rhizobium inoculant
Answer: a
- a) Correct: Bt formulations sprayed on crops.
Q121. Why is Bacillus thuringiensis toxin safe for humans?
a) It is active only in acidic pH
b) It is active only in insect gut alkaline pH
c) It is digested by humans as protein
d) Both b and c
Answer: d
- d) Correct: Bt toxin activated in alkaline insect gut, digested safely in humans.
Q122. Which biocontrol agent is used in paddy fields to control pests?
a) Baculovirus
b) Bacillus thuringiensis
c) Ladybird beetle
d) Dragonfly
Answer: b
- b) Correct: Bt formulations are sprayed in rice fields.
Q123. Example of conservation biocontrol is:
a) Maintaining habitats of natural predators like ladybird beetles
b) Spraying Bt
c) Using antibiotics
d) UV sterilization
Answer: a
- a) Correct: Conservation biocontrol = protect natural predators.
Q124. Which microbial biocontrol method prevents fungal wilt in plants?
a) Bt spray
b) Trichoderma in soil
c) Baculovirus
d) Ladybird beetle
Answer: b
- b) Correct: Trichoderma reduces soil-borne fungal diseases.
Q125. Use of microbial biocontrol is an example of:
a) Organic farming practice
b) Chemical pesticide use
c) Hybrid crop development
d) Irrigation method
Answer: a
- a) Correct: Biocontrol fits well in organic farming.
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