PCA WEEDS UPDATED 2026 EXAM SCRIPT QUESTIONS
AND SOLUTIONS SCORED A+
✔✔thiocarbamates (EPTC, thiobencarb); - ✔✔MoA-
✔✔triazines (atrazine, simazine); - ✔✔MoA- act as inhibitors of plastoquinone binding;
inhibits Photosystem II
✔✔ureas (linuron, diuron). - ✔✔MoA- foliar absorbed and residual herbicide. inhibits
photosynthesis at photosystem II
✔✔phytotoxicity; - ✔✔Injury or damage to a sensitive plant caused by a chemical
exposure.
✔✔adjuvant; - ✔✔ormulation or added to the spray tank to improve herbicidal activity or
application characteristics.
✔✔cross-resistance; - ✔✔Refers to a biotype that is resistant to two or more chemically
similar herbicides
✔✔multiple resistance; - ✔✔Refers to weed biotype that is resistant to two or more
chemically unrelated herbicides
✔✔plantback restrictions. - ✔✔some pesticides can adversely affect the growth of
sensitive rotational crops or because a tolerance for the active ingredient has not been
established for the next crop in rotation.
✔✔Describe soil conditions that: increase the persistence or availability of most soil-
applied herbicides. - ✔✔Are held tightly in soils that have high clay content or high
levels or OM. Results- have to increase herbicide usage.
✔✔Biotype - ✔✔a group of organisms having an identical genetic constitution.
✔✔Ecotype - ✔✔a distinct form or race of a plant or animal species occupying a
particular habitat.
✔✔Describe the impact of weed biotypes on
herbicide resistance. - ✔✔If one uses same herbicide on same biotypes too much,
resistance can develop.
✔✔herbicide tolerance vs herbicide resistance in weeds. - ✔✔Tolerance- Plant
populations survive, naturally immune to a particular herbicide, when applied at labeled
use rate
, Resistance- Ability of a biotype to survive a treatment with a given herbicide to which
the weed species is normally susceptible
✔✔Soil texture - ✔✔as soil texture and OM increase, one must use more herbicides.
✔✔pH - ✔✔pH affects the herbicides ability to be absorbed.
✔✔List the economic factors to be considered in a weed management program. -
✔✔Worth spending 'x' amount to save crop, ID pest, if I apply this over that product is it
worth
✔✔Identify the factors that contribute to herbicide leaching to ground water. -
✔✔Overuse, drift into water ways, runoff into waterways, applying then irrigating
✔✔shielded; - ✔✔A sprayer the is shielded keeping all contents within that area.
✔✔List factors that affect the behavior of herbicides in the soil and the environment. -
✔✔pH, OM content, soil texture + moisture, amount of clay, porosity
✔✔Redroot pigweed* - ✔✔Annual
✔✔Yellow starthistle* - ✔✔Annual
✔✔Hairy fleabane* - ✔✔Annual
✔✔Horseweed - ✔✔Annual
✔✔Prickly lettuce* - ✔✔
✔✔Common groundsel* - ✔✔
✔✔Annual sowthistle - ✔✔
✔✔Coast fiddleneck* - ✔✔
✔✔Black mustard* - ✔✔
✔✔Shepherd's-purse* - ✔✔
✔✔London rocket - ✔✔
✔✔Common chickweed* - ✔✔
AND SOLUTIONS SCORED A+
✔✔thiocarbamates (EPTC, thiobencarb); - ✔✔MoA-
✔✔triazines (atrazine, simazine); - ✔✔MoA- act as inhibitors of plastoquinone binding;
inhibits Photosystem II
✔✔ureas (linuron, diuron). - ✔✔MoA- foliar absorbed and residual herbicide. inhibits
photosynthesis at photosystem II
✔✔phytotoxicity; - ✔✔Injury or damage to a sensitive plant caused by a chemical
exposure.
✔✔adjuvant; - ✔✔ormulation or added to the spray tank to improve herbicidal activity or
application characteristics.
✔✔cross-resistance; - ✔✔Refers to a biotype that is resistant to two or more chemically
similar herbicides
✔✔multiple resistance; - ✔✔Refers to weed biotype that is resistant to two or more
chemically unrelated herbicides
✔✔plantback restrictions. - ✔✔some pesticides can adversely affect the growth of
sensitive rotational crops or because a tolerance for the active ingredient has not been
established for the next crop in rotation.
✔✔Describe soil conditions that: increase the persistence or availability of most soil-
applied herbicides. - ✔✔Are held tightly in soils that have high clay content or high
levels or OM. Results- have to increase herbicide usage.
✔✔Biotype - ✔✔a group of organisms having an identical genetic constitution.
✔✔Ecotype - ✔✔a distinct form or race of a plant or animal species occupying a
particular habitat.
✔✔Describe the impact of weed biotypes on
herbicide resistance. - ✔✔If one uses same herbicide on same biotypes too much,
resistance can develop.
✔✔herbicide tolerance vs herbicide resistance in weeds. - ✔✔Tolerance- Plant
populations survive, naturally immune to a particular herbicide, when applied at labeled
use rate
, Resistance- Ability of a biotype to survive a treatment with a given herbicide to which
the weed species is normally susceptible
✔✔Soil texture - ✔✔as soil texture and OM increase, one must use more herbicides.
✔✔pH - ✔✔pH affects the herbicides ability to be absorbed.
✔✔List the economic factors to be considered in a weed management program. -
✔✔Worth spending 'x' amount to save crop, ID pest, if I apply this over that product is it
worth
✔✔Identify the factors that contribute to herbicide leaching to ground water. -
✔✔Overuse, drift into water ways, runoff into waterways, applying then irrigating
✔✔shielded; - ✔✔A sprayer the is shielded keeping all contents within that area.
✔✔List factors that affect the behavior of herbicides in the soil and the environment. -
✔✔pH, OM content, soil texture + moisture, amount of clay, porosity
✔✔Redroot pigweed* - ✔✔Annual
✔✔Yellow starthistle* - ✔✔Annual
✔✔Hairy fleabane* - ✔✔Annual
✔✔Horseweed - ✔✔Annual
✔✔Prickly lettuce* - ✔✔
✔✔Common groundsel* - ✔✔
✔✔Annual sowthistle - ✔✔
✔✔Coast fiddleneck* - ✔✔
✔✔Black mustard* - ✔✔
✔✔Shepherd's-purse* - ✔✔
✔✔London rocket - ✔✔
✔✔Common chickweed* - ✔✔
