2025 PCA WEEDS ACTUAL EXAM QUESTIONS EVALUATION WITH
ANSWERS GUARANTEE A+ 2025/2026
Describe the impact of synthetic mulches on weeds. - Synthetic mulches such as plastic
can block sunlight from reaching weed seeds and preventing germination.
Describe the impact of organic mulches on weeds. - Prevent germination of weed seeds
by keeping the shallow layer dry and giving the crop seed a head start
Describe the impact of sanitation methods on weeds. - Sanitation of equipment and
irrigation water (screens) can reduce the amount of weed seed moved to different parts
of the field or different fields
List and describe common cultivation/tillage methods. - Rolling cultivators, plant hoe, V-
sweep, cultivator knife, bed knives, shovels, vegetable knives, Alabama sweeps, chisel
plow sweeps, cultivator sweeps
Describe how weeds are affected by depth of tillage. - Small weed seed won't germinate
if buried deep but larger seed will. Vegetative propagation will not re-emerge if buried
deep enough but it is difficult.
Describe how weeds are affected by timing of tillage. - Dormant seed will be more likely
to not emerge if tillage is done during dormancy. Freshly emerged seed should be tilled
immediately to eliminate the weed. Vegetative propagation needs to be tilled/removed
before periods of rapid growth.
Describe how weeds are affected by no-tillage. - No-tillage can promote weed growth
unless no-tillage is used with different methods of control such as mulches.
Describe cultivation techniques used in perennial crops. - Mechanical cultivation used
for seedbed preparation and then hand cultivation used in rows after perennial crop
growth.
Compare the advantages and disadvantages of different cultivation methods. - Hand
cultivation: can be closer to the crop but expensive to pay for labor and room for human
error
Mechanical cultivation: inexpensive, but time consuming and often needs a crew to
hand cultivate behind the equipment
Identify the proper timing for cultivation and hand weeding. - When weeds have just
emerged
Describe the use of the following methods for weed control: burning and flaming -
Flaming is used to over heat weeds instead of burning, but it is used to burn the outer
layer and allow for dessication
, Describe the use of the following methods for weed control: steaming and solarization -
Use of moisture and heat with tarp to over heat weeds and kill them
Describe how control measures using heat affect weed and crop growth. - If not directed
carefully, heat can also damage crop growth. Heat will disrupt epidermal cells of the
plant to induce moisture loss and effectively dry out the plant.
Describe some preventative measures that can be used to manage weeds (certified
seed, quarantines, clean equipment) - Certified seed helps prevent introduction of
weeds such as dodder that have seed that look identical to crop seed. Quarantines help
prevent spread of weeds by setting seed aside or crops aside to eliminate weeds. Clean
equipment helps prevent movement of seed to different fields or spots within a field.
List the various methods used to classify herbicides. - Usage, contact or systemic,
method of translocation, method of application, selectivity, time of application, plant
symptomology, toxicology, chemistry
Define mode of action and the results of using an herbicide with a given mode of action
- Mode of action is the way in which an herbicide controls a weed. For example, any
herbicide that disrupts cell membranes will have similar plant symptoms.
Amides (propanil) - Photosynthesis inhibitors
Bipryidiliums (paraquat, diquat) - Electron acceptors - PSI (accepts electrons to form
toxic free radicals)
Dinitroanilines (trifluralin, pendimethalin) - MoA- inhibition of cell mitosis
Diphenylethers (oxyfluorfen) - Free radical generators; destruction of cell membranes
Glycine (glyphosate) - EPSP Synthase Inhibitors, interferes with normal carbohydrate
translocation in plants
Phenoxy carboxylic acids (auxinic herbicides, 2,4-D) - Growth regulators, regulate plant
cell growth and differentiation
Phosphinic acid (glufosinate) - MoA- glutamine synthetase inhibitor that binds to the
glutamate site. die due to a buildup of ammonia in the thylakoid lumen
Sulfonylureas (Chlorsulfuron, rimsulfuron) - MoA- direct inhibition of DNA synthesis.
Inhibits ALS/AhAS which is the first step in the synthesis of the branched-chain amino
acids valine, leucine and isoleucine
Thiocarbamates (EPTC, thiobencarb) - Energy production inhibitors. Inhibits lipid
synthesis and cell division.
ANSWERS GUARANTEE A+ 2025/2026
Describe the impact of synthetic mulches on weeds. - Synthetic mulches such as plastic
can block sunlight from reaching weed seeds and preventing germination.
Describe the impact of organic mulches on weeds. - Prevent germination of weed seeds
by keeping the shallow layer dry and giving the crop seed a head start
Describe the impact of sanitation methods on weeds. - Sanitation of equipment and
irrigation water (screens) can reduce the amount of weed seed moved to different parts
of the field or different fields
List and describe common cultivation/tillage methods. - Rolling cultivators, plant hoe, V-
sweep, cultivator knife, bed knives, shovels, vegetable knives, Alabama sweeps, chisel
plow sweeps, cultivator sweeps
Describe how weeds are affected by depth of tillage. - Small weed seed won't germinate
if buried deep but larger seed will. Vegetative propagation will not re-emerge if buried
deep enough but it is difficult.
Describe how weeds are affected by timing of tillage. - Dormant seed will be more likely
to not emerge if tillage is done during dormancy. Freshly emerged seed should be tilled
immediately to eliminate the weed. Vegetative propagation needs to be tilled/removed
before periods of rapid growth.
Describe how weeds are affected by no-tillage. - No-tillage can promote weed growth
unless no-tillage is used with different methods of control such as mulches.
Describe cultivation techniques used in perennial crops. - Mechanical cultivation used
for seedbed preparation and then hand cultivation used in rows after perennial crop
growth.
Compare the advantages and disadvantages of different cultivation methods. - Hand
cultivation: can be closer to the crop but expensive to pay for labor and room for human
error
Mechanical cultivation: inexpensive, but time consuming and often needs a crew to
hand cultivate behind the equipment
Identify the proper timing for cultivation and hand weeding. - When weeds have just
emerged
Describe the use of the following methods for weed control: burning and flaming -
Flaming is used to over heat weeds instead of burning, but it is used to burn the outer
layer and allow for dessication
, Describe the use of the following methods for weed control: steaming and solarization -
Use of moisture and heat with tarp to over heat weeds and kill them
Describe how control measures using heat affect weed and crop growth. - If not directed
carefully, heat can also damage crop growth. Heat will disrupt epidermal cells of the
plant to induce moisture loss and effectively dry out the plant.
Describe some preventative measures that can be used to manage weeds (certified
seed, quarantines, clean equipment) - Certified seed helps prevent introduction of
weeds such as dodder that have seed that look identical to crop seed. Quarantines help
prevent spread of weeds by setting seed aside or crops aside to eliminate weeds. Clean
equipment helps prevent movement of seed to different fields or spots within a field.
List the various methods used to classify herbicides. - Usage, contact or systemic,
method of translocation, method of application, selectivity, time of application, plant
symptomology, toxicology, chemistry
Define mode of action and the results of using an herbicide with a given mode of action
- Mode of action is the way in which an herbicide controls a weed. For example, any
herbicide that disrupts cell membranes will have similar plant symptoms.
Amides (propanil) - Photosynthesis inhibitors
Bipryidiliums (paraquat, diquat) - Electron acceptors - PSI (accepts electrons to form
toxic free radicals)
Dinitroanilines (trifluralin, pendimethalin) - MoA- inhibition of cell mitosis
Diphenylethers (oxyfluorfen) - Free radical generators; destruction of cell membranes
Glycine (glyphosate) - EPSP Synthase Inhibitors, interferes with normal carbohydrate
translocation in plants
Phenoxy carboxylic acids (auxinic herbicides, 2,4-D) - Growth regulators, regulate plant
cell growth and differentiation
Phosphinic acid (glufosinate) - MoA- glutamine synthetase inhibitor that binds to the
glutamate site. die due to a buildup of ammonia in the thylakoid lumen
Sulfonylureas (Chlorsulfuron, rimsulfuron) - MoA- direct inhibition of DNA synthesis.
Inhibits ALS/AhAS which is the first step in the synthesis of the branched-chain amino
acids valine, leucine and isoleucine
Thiocarbamates (EPTC, thiobencarb) - Energy production inhibitors. Inhibits lipid
synthesis and cell division.
