2025 PCA WEEDS REAL EXAM EVALUATION QUESTIONS WITH
ANSWERS GUARANTEE A+ 2025/2026
Describe the influence of seasonal changes on the weed spectrum - Different seasons
will see different groups of weeds present in fields (winter vs summer annuals)
Describe the influence of weed growth on water and nutrient availability to the crop. -
Weeds will out-compete crops for water and nutrient availability, hence why it is
important to manage weeds before they become out of control.
Describe the influence of temperature on plant growth. - Warmer temperatures will lead
to increased plant growth but too hot of temperatures can damage plants and retard
their growth
Recognize the importance of light and space in plant growth and development - Plants
need space from other plants as well as adequate light to grow and develop
Reproductive capability of weeds - Weeds can produce seed which can be dispersed
across space, or they can produce propagules which make them very persistent and
difficult to manage
Seeds are only way for annuals and biennials to reproduce.
Propagules are how perennials reproduce and allow for recovery from mechanical
damage.
Describe the mechanisms by which weed seeds are disseminated. - Weed seeds can
be dispersed naturally by wind, water, and animals. They can also be dispersed via
tumbling weeds. They can also be dispersed by humans such as on equipment, in soil
on equipment, or seeds that puncture tires.
Describe how biotic factors of the environment contribute to regulating the seed bank
and seed longevity. - Natural decay can break seed dormancy which if left unmanaged
can replenish the seed bank. Biotic factors can replenish the weed seed bank.
Describe how loss of seed viability contributes to regulating the seed bank and seed
longevity. - Loss of seed viability reduces the amount of weeds that are able to
germinate and reproduce more seed. If a seed bank were to theoretically become
unviable, there would be no weed problems.
Describe how production practices, such as applications of preemergence herbicides,
contribute to regulating the seed bank and seed longevity. - Preemergence herbicides
can reduce the amount of weeds that emerge and have the potential to set seed, thus
reducing the seed bank as well as seed longevity.
Describe how cultural practices contribute to regulating the seed bank and seed
longevity. - Cultural practices, such as preirrigation or crop rotation, can reduce the
,seed bank and longevity by germinating weed seeds to be cultivated, or rotating to a
crop that outcompetes the current weed seeds.
Describe how different types of vegetative propagules spread. - When weeds with
vegetative propagules are fragmented, they can be spread to different fields or parts of
the field.
Describe how to map a field in relationship to weed management considerations. - A
field should be mapped to show what weeds are present, where the weeds are present,
how many weeds are present, and if there are any factors that will influence the choice
of management (water sources, sensitive sites, etc)
List information necessary to document a field's weed history - Cropping history, weeds
prevalent, areas of high weed pressure
Absolute sampling - Sampling to count every individual in a given area
Relative sampling - Sampling to give an estimate of a total population by sampling a
proportion of a population in a given area
Random sampling patterns - Every sample unit has an equal chance of selection
Stratified sampling patterns - Partitions the habitat into subunits that may vary in
character, each subunit is then independently sampled
Systematic sampling patterns - Each sample unit is chosen systematically from a
randomly selected starting point, such as every 50th plant or every 5 feet.
Identify essential times during which monitoring should be done for annual weeds -
Winter annuals during fall and winter, summer annuals during spring and summer
Identify essential times during which monitoring should be done for perennial weeds - At
all times aware that some species are dormant during some seasons
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.
ANSWERS GUARANTEE A+ 2025/2026
Describe the influence of seasonal changes on the weed spectrum - Different seasons
will see different groups of weeds present in fields (winter vs summer annuals)
Describe the influence of weed growth on water and nutrient availability to the crop. -
Weeds will out-compete crops for water and nutrient availability, hence why it is
important to manage weeds before they become out of control.
Describe the influence of temperature on plant growth. - Warmer temperatures will lead
to increased plant growth but too hot of temperatures can damage plants and retard
their growth
Recognize the importance of light and space in plant growth and development - Plants
need space from other plants as well as adequate light to grow and develop
Reproductive capability of weeds - Weeds can produce seed which can be dispersed
across space, or they can produce propagules which make them very persistent and
difficult to manage
Seeds are only way for annuals and biennials to reproduce.
Propagules are how perennials reproduce and allow for recovery from mechanical
damage.
Describe the mechanisms by which weed seeds are disseminated. - Weed seeds can
be dispersed naturally by wind, water, and animals. They can also be dispersed via
tumbling weeds. They can also be dispersed by humans such as on equipment, in soil
on equipment, or seeds that puncture tires.
Describe how biotic factors of the environment contribute to regulating the seed bank
and seed longevity. - Natural decay can break seed dormancy which if left unmanaged
can replenish the seed bank. Biotic factors can replenish the weed seed bank.
Describe how loss of seed viability contributes to regulating the seed bank and seed
longevity. - Loss of seed viability reduces the amount of weeds that are able to
germinate and reproduce more seed. If a seed bank were to theoretically become
unviable, there would be no weed problems.
Describe how production practices, such as applications of preemergence herbicides,
contribute to regulating the seed bank and seed longevity. - Preemergence herbicides
can reduce the amount of weeds that emerge and have the potential to set seed, thus
reducing the seed bank as well as seed longevity.
Describe how cultural practices contribute to regulating the seed bank and seed
longevity. - Cultural practices, such as preirrigation or crop rotation, can reduce the
,seed bank and longevity by germinating weed seeds to be cultivated, or rotating to a
crop that outcompetes the current weed seeds.
Describe how different types of vegetative propagules spread. - When weeds with
vegetative propagules are fragmented, they can be spread to different fields or parts of
the field.
Describe how to map a field in relationship to weed management considerations. - A
field should be mapped to show what weeds are present, where the weeds are present,
how many weeds are present, and if there are any factors that will influence the choice
of management (water sources, sensitive sites, etc)
List information necessary to document a field's weed history - Cropping history, weeds
prevalent, areas of high weed pressure
Absolute sampling - Sampling to count every individual in a given area
Relative sampling - Sampling to give an estimate of a total population by sampling a
proportion of a population in a given area
Random sampling patterns - Every sample unit has an equal chance of selection
Stratified sampling patterns - Partitions the habitat into subunits that may vary in
character, each subunit is then independently sampled
Systematic sampling patterns - Each sample unit is chosen systematically from a
randomly selected starting point, such as every 50th plant or every 5 feet.
Identify essential times during which monitoring should be done for annual weeds -
Winter annuals during fall and winter, summer annuals during spring and summer
Identify essential times during which monitoring should be done for perennial weeds - At
all times aware that some species are dormant during some seasons
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.
