Herbicides: Types, Modes of Action, Application & Sprayer Calibration

Question No. 1 Marks +1 -0 Time

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Which of the following describes a herbicide that is applied to the soil before the crop or weeds emerge, targeting germinating seeds or very young seedlings?

A. Post-emergent herbicide
B. Contact herbicide
C. Pre-emergent herbicide
D. Systemic herbicide

Question No. 2 Marks +1 -0 Time

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Herbicides like Glyphosate are known for their mode of action which inhibits the EPSPS enzyme pathway. What critical process in plants does this pathway primarily affect?

A. Lipid synthesis
B. Amino acid synthesis
C. Photosynthesis
D. Cell division

Question No. 3 Marks +1 -0 Time

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Consider the following statements regarding herbicide application:

1. Band application involves treating only a narrow strip over or alongside the crop row.
2. Broadcast application covers the entire area uniformly.
3. Spot application is used for treating individual weeds or small patches.

Which of the statements are correct?

A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2, and 3

Question No. 4 Marks +1 -0 Time

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A farmer is calibrating a boom sprayer and needs to apply a herbicide at a rate of 20 gallons per acre (GPA). The sprayer's effective swath width is 20 feet, and the tractor speed is 4 miles per hour (MPH). What should be the total flow rate from all nozzles in gallons per minute (GPM)?

(Hint: 1 acre = 43,560 sq ft, 1 mile = 5280 ft)

A. 2.67 GPM
B. 3.23 GPM
C. 4.15 GPM
D. 5.33 GPM

Question No. 5 Marks +1 -0 Time

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Which type of herbicide primarily works by disrupting the cell membranes of plants, leading to rapid desiccation and necrosis of plant tissues upon contact?

A. Photosystem II inhibitors (e.g., Atrazine)
B. Auxinic herbicides (e.g., 2,4-D)
C. Cell membrane disruptors (e.g., Paraquat)
D. ALS inhibitors (e.g., Sulfonylureas)

Question No. 6 Marks +1 -0 Time

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Match the following herbicide types with their primary mode of action:

Herbicide Type	Mode of Action
1. Phenoxy herbicides	P. Inhibition of lipid synthesis
2. Triazine herbicides	Q. Disruption of cell growth (auxin mimic)
3. ACCase inhibitors	R. Inhibition of Photosystem II
4. Glyphosate	S. Inhibition of EPSPS enzyme

A. 1-Q, 2-R, 3-P, 4-S
B. 1-R, 2-Q, 3-S, 4-P
C. 1-Q, 2-S, 3-P, 4-R
D. 1-S, 2-P, 3-R, 4-Q

Question No. 7 Marks +1 -0 Time

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Which of the following statements about selective herbicides is most accurate?

A. They kill all plant species they come into contact with.
B. They are designed to kill only grasses and leave broadleaf weeds unharmed.
C. They differentiate between crop and weed species, killing specific weeds while leaving the crop relatively unaffected.
D. They are always applied pre-emergence to prevent crop damage.

Question No. 8 Marks +1 -0 Time

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A farmer notices that a newly applied herbicide is causing severe phytotoxicity to the crop, even though the correct product and rate were used. Which of the following is a likely cause related to application conditions?

A. Application during a period of high humidity and calm winds.
B. Application during very hot and dry conditions, leading to rapid absorption.
C. Application at night when temperatures are cooler.
D. Application with a larger nozzle size than recommended.

Question No. 9 Marks +1 -0 Time

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Which of the following is a key advantage of using systemic herbicides over contact herbicides?

A. They provide faster weed control, often within hours.
B. They are effective against perennial weeds with extensive root systems.
C. They are less prone to environmental degradation.
D. They typically require lower application rates for efficacy.

Question No. 10 Marks +1 -0 Time

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When calibrating a sprayer, what would be the impact of increasing the operating pressure while keeping the nozzle type and speed constant?

A. Decrease in flow rate and larger droplet size.
B. Increase in flow rate and smaller droplet size.
C. No change in flow rate, but larger droplet size.
D. Decrease in flow rate and smaller droplet size.

Question No. 11 Marks +1 -0 Time

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Rank the following application methods from most precise (targeting individual plants) to least precise (broad coverage):

1. Broadcast application
2. Spot application
3. Band application

A. 1, 3, 2
B. 2, 3, 1
C. 3, 2, 1
D. 2, 1, 3

Question No. 12 Marks +1 -0 Time

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Which of the following pairs correctly links a herbicide with its common chemical family?

A. 2,4-D - Sulfonylurea
B. Atrazine - Phenoxy
C. Glyphosate - Organophosphate
D. Paraquat - Carbamate

Question No. 13 Marks +1 -0 Time

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Adjuvants are substances added to a spray tank to improve the efficacy or handling of a herbicide. Which type of adjuvant is primarily used to reduce surface tension of water, allowing spray droplets to spread more evenly on leaf surfaces?

A. Drift retardant
B. Buffer
C. Surfactant
D. Crop oil concentrate

Question No. 14 Marks +1 -0 Time

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A sprayer is calibrated to deliver 15 gallons per acre (GPA). If the nozzle output is 0.2 GPM and the nozzle spacing is 20 inches, what speed (in MPH) should the sprayer travel?

A. 3.5 MPH
B. 4.1 MPH
C. 5.3 MPH
D. 6.0 MPH

Question No. 15 Marks +1 -0 Time

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Which mode of action describes herbicides that inhibit the Acetyl-CoA carboxylase (ACCase) enzyme, thereby preventing the synthesis of fatty acids and lipids essential for plant growth?

A. Photosynthesis inhibition
B. Auxin mimicry
C. Cell division inhibition
D. Lipid synthesis inhibition

Question No. 16 Marks +1 -0 Time

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How many of the following pairs correctly associate a herbicide application factor with its typical effect on herbicide efficacy?

1. High soil organic matter : Reduced herbicide availability to weeds
2. Low soil moisture : Reduced herbicide uptake by roots
3. High air temperature : Increased herbicide volatilization
4. Large weed size : Increased herbicide translocation

A. One
B. Two
C. Three
D. Four

Question No. 17 Marks +1 -0 Time

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What is the primary purpose of a drift retardant adjuvant in herbicide application?

A. To increase the spreading of spray droplets on leaf surfaces.
B. To reduce the evaporation of spray droplets.
C. To increase the viscosity of the spray solution, leading to larger droplets.
D. To improve the solubility of the herbicide in water.

Question No. 18 Marks +1 -0 Time

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Which of the following herbicide groups primarily inhibits the enzyme acetolactate synthase (ALS), also known as acetohydroxyacid synthase (AHAS), leading to a blockage in the synthesis of branched-chain amino acids?

A. Glyphosate and Glufosinate
B. Triazines and Phenylureas
C. Sulfonylureas and Imidazolinones
D. Bipyridyliums and Dinitroanilines

Question No. 19 Marks +1 -0 Time

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A contact herbicide is generally most effective when applied to which of the following?

A. Perennial weeds with deep root systems.
B. Weeds with thick, waxy cuticles.
C. Small, actively growing annual weeds.
D. Weeds in conditions of high environmental stress.

Question No. 20 Marks +1 -0 Time

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When performing sprayer calibration, what is the most critical factor to measure accurately to ensure the correct application rate?

A. The color of the spray solution.
B. The ambient air temperature.
C. The actual volume sprayed per unit time (e.g., GPM per nozzle).
D. The type of crop being sprayed.

Question No. 21 Marks +1 -0 Time

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Which of the following statements about herbicide resistance is true?

A. Herbicide resistance in weeds is always caused by genetic modification.
B. Repeated use of herbicides with different modes of action accelerates resistance development.
C. Resistance often develops due to a single, specific mechanism in the weed population.
D. Integrated Weed Management (IWM) strategies are crucial for preventing and managing herbicide resistance.

Question No. 22 Marks +1 -0 Time

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Consider the chronological order of events when a systemic, post-emergent herbicide is applied to a susceptible weed:

1. Herbicide translocation to sites of action.
2. Visible symptoms of injury appear.
3. Herbicide absorption by foliage.
4. Disruption of biochemical processes.

Which sequence correctly represents the typical progression?

A. 3 → 1 → 4 → 2
B. 1 → 3 → 4 → 2
C. 3 → 4 → 1 → 2
D. 2 → 3 → 1 → 4

Question No. 23 Marks +1 -0 Time

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Which of the following statements best describes a 'residual herbicide'?

A. A herbicide that is quickly broken down in the environment and has no lasting effect.
B. A herbicide that remains active in the soil for an extended period, providing control of germinating weeds.
C. A herbicide that only kills the parts of the plant it directly contacts.
D. A herbicide that is absorbed by the plant and translocated throughout its system.

Question No. 24 Marks +1 -0 Time

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A farmer is trying to reduce the potential for herbicide drift during application. Which of the following adjustments would be most effective?

A. Increasing the sprayer pressure and using smaller nozzles.
B. Decreasing the boom height and increasing the travel speed.
C. Using larger spray nozzles and decreasing the sprayer pressure.
D. Applying during high wind conditions to ensure wide coverage.

Question No. 25 Marks +1 -0 Time

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Match the following herbicide resistance mechanisms with their descriptions:

Mechanism	Description
1. Target-site resistance	P. Weed plant metabolizes the herbicide into a non-toxic form.
2. Non-target-site resistance	Q. Changes in the herbicide's binding site on the target enzyme.
3. Enhanced metabolism	R. Reduced herbicide uptake or increased efflux from cells.
4. Altered translocation	S. Herbicide fails to move effectively to its site of action.

A. 1-Q, 2-R, 3-P, 4-S
B. 1-P, 2-Q, 3-R, 4-S
C. 1-Q, 2-P, 3-R, 4-S
D. 1-R, 2-Q, 3-P, 4-S

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