2025 PCA WEEDS ALL QUIZ EXAM QUESTIONS WITH ANSWERS
GUARANTEE A+ 2025/2026
Define biological control - Use of organism or byproducts of living organisms to
suppress or kill pests
Describe and give an example of biological weed control using arthropods. - -Gall
forming mite (Aceria chondrillae) on rush skeletonweed
-Tetranychus lintearius to control gorse
-Cinnabar moth (Tyria jacobaea) on tansy ragwort
-Ragwort seed fly (Botanophila seneciella) on tansy ragwort
-Ragwort flea beetle (Longistarsus jacobaeae) on tansy ragwort
-Klamath weed beetle (Chrysolina quadrigemina) on Klamath weed/St. Johnswort
Describe and give an example of biological weed control using pathogens. - -
Xanthamonas campestris pv. poannua to control unwanted grass species
-Phyllocoptes fructiphilus to kill multiflora rose
-Puccinia carduorum to control musk thistle
Describe and give an example of biological weed control using grazing animals. - -
Young stages of Yellow starthistle
-Grass carp
Identify the factors that would limit the use of biological control for weeds. - Agent may
attack non-target species, need species with high specificity to the target weed, some
agents may not exist for pest weeds, program is expensive and takes a long time,
unexpected factors such as environment or other predators of control agent
Describe the impact of seedbed preparation on weeds. - Secondary tillage can eliminate
existing vegetation, apply fertilizer only where crops will be planted, remove weeds as
seedling crops as emerging, dislodging small weeds
Describe the impact of irrigation method on weeds. - Different weeds will grow in
different irrigation methods (drip vs sprinkler vs flood). Managing the irrigation method to
provide adequate water to crop but reduce water to weeds (drip) can help reduce weed
populations
Describe the impact of irrigation timing on weeds. - Preplant irrigation to remove
germinated weeds. Not irrigating after cultivation to allow weeds to dry out and die.
Describe the impact of time of seeding on weeds. - Time seeding to outcompete weeds
to reduce weed pressure. Do not seed if weeds have emerged.
Describe the impact of soil nutrition on weeds. - If soil nutrients are directed to other
spots than where the crops will uptake them, then the weeds will take up nutrients and
try to out-compete the crop being grown
,Describe the impact of seed/plant spacing on weeds. - If there is not enough room for
weeds to receive light or water, crops will out-compete weeds
Describe the impact of crop variety on weeds. - Select for varieties that grow quickly
and develop canopies to shade out weeds to reduce susceptibility to weed competition
Describe the impact of crop rotation on weeds. - Allows for diverse methods to manage
weeds. Diversification of crops grown reduces and prevents the proliferation of weed
species acclimated to a monoculture
Describe the impact of pre-irrigation on weeds. - Pre-irrigation can germinate weed
seed present and allow for easy cultivation before planting.
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
GUARANTEE A+ 2025/2026
Define biological control - Use of organism or byproducts of living organisms to
suppress or kill pests
Describe and give an example of biological weed control using arthropods. - -Gall
forming mite (Aceria chondrillae) on rush skeletonweed
-Tetranychus lintearius to control gorse
-Cinnabar moth (Tyria jacobaea) on tansy ragwort
-Ragwort seed fly (Botanophila seneciella) on tansy ragwort
-Ragwort flea beetle (Longistarsus jacobaeae) on tansy ragwort
-Klamath weed beetle (Chrysolina quadrigemina) on Klamath weed/St. Johnswort
Describe and give an example of biological weed control using pathogens. - -
Xanthamonas campestris pv. poannua to control unwanted grass species
-Phyllocoptes fructiphilus to kill multiflora rose
-Puccinia carduorum to control musk thistle
Describe and give an example of biological weed control using grazing animals. - -
Young stages of Yellow starthistle
-Grass carp
Identify the factors that would limit the use of biological control for weeds. - Agent may
attack non-target species, need species with high specificity to the target weed, some
agents may not exist for pest weeds, program is expensive and takes a long time,
unexpected factors such as environment or other predators of control agent
Describe the impact of seedbed preparation on weeds. - Secondary tillage can eliminate
existing vegetation, apply fertilizer only where crops will be planted, remove weeds as
seedling crops as emerging, dislodging small weeds
Describe the impact of irrigation method on weeds. - Different weeds will grow in
different irrigation methods (drip vs sprinkler vs flood). Managing the irrigation method to
provide adequate water to crop but reduce water to weeds (drip) can help reduce weed
populations
Describe the impact of irrigation timing on weeds. - Preplant irrigation to remove
germinated weeds. Not irrigating after cultivation to allow weeds to dry out and die.
Describe the impact of time of seeding on weeds. - Time seeding to outcompete weeds
to reduce weed pressure. Do not seed if weeds have emerged.
Describe the impact of soil nutrition on weeds. - If soil nutrients are directed to other
spots than where the crops will uptake them, then the weeds will take up nutrients and
try to out-compete the crop being grown
,Describe the impact of seed/plant spacing on weeds. - If there is not enough room for
weeds to receive light or water, crops will out-compete weeds
Describe the impact of crop variety on weeds. - Select for varieties that grow quickly
and develop canopies to shade out weeds to reduce susceptibility to weed competition
Describe the impact of crop rotation on weeds. - Allows for diverse methods to manage
weeds. Diversification of crops grown reduces and prevents the proliferation of weed
species acclimated to a monoculture
Describe the impact of pre-irrigation on weeds. - Pre-irrigation can germinate weed
seed present and allow for easy cultivation before planting.
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
