PCA WEEDS LATEST 2026 TEST PAPER QUESTIONS AND
SOLUTIONS SCORED A+
✔✔Dry flowable (DF), dispersible granule (DG), water dispersible granule (WDG) -
✔✔Form suspension, requires agitation, flow easily out of container to reduce dust
problem WP have
✔✔Aqueous solution (AS), flowable (F), liquid flowable (L) - ✔✔Liquid formulation
requiring agitation in a spray tank
✔✔Emulsifiable concentrate (E or EC) - ✔✔For AI with low water solubility. Forms an
emulsion in water
✔✔Soluble concentrate (S, SC), soluble powder (SP), water-soluble concentrate (WSC)
- ✔✔Low volatility, not abrasive, form a solution in tank, do not require agitation
✔✔List reasons for adding an adjuvant to an herbicide formulation. - ✔✔To enhance or
modify the solution. Enhance the emulsifying, dispersing, spreading, sticking, or wetting
properties of liquids. Reduce runoff, uniform spread
✔✔Describe soil conditions that enhance the degradation of herbicides. - ✔✔Microbial
activities, pH below 6, light absorption, water
✔✔Describe soil conditions that increase the persistence or availability of soil applied
herbicides. - ✔✔Soil type, soil temperature, management practices, application method
✔✔Biotype - ✔✔organisms/structures with same genetic makeup resulting in similarity
in appearance
✔✔Ecotype - ✔✔a population adapted to its unique local environmental conditions
✔✔Describe the impact of weed biotypes on herbicide resistance. - ✔✔Weed biotypes
can lead to an entire group of weeds developing resistance to an herbicide because of
the identical genetic makeup
✔✔Describe how knowledge of the herbicide mode of action/group number aids in
resistance management. - ✔✔Rotating between different modes of action can reduce
the possibility of a weed developing resistance to a particular mode of action.
✔✔Differentiate between herbicide tolerance and herbicide resistance in weeds. -
✔✔Herbicide tolerance is ability of a weed to tolerate an herbicide due to a physical
feature, whereas resistance is genetic coding that enables a weed to completely resist
an herbicide.
, ✔✔Describe methods used to prevent and manage pesticide resistance. - ✔✔Rotating
to herbicides with different modes of action, using non-chemical controls, crop rotations,
etc.
✔✔Describe the importance of crop rotation in managing herbicide resistance -
✔✔Weeds may be crop specific, so rotation can help reduce weed pressure and reduce
the amount of weeds that out compete a particular crop
✔✔Describe how herbicide solubility affects herbicide movement in the soil. - ✔✔Water
soluble herbicides move easier with water than those that are not soluble.
✔✔Describe how soil texture affects herbicide movement in the soil. - ✔✔Some
textures, such as clay, will hold onto herbicides more tightly than a texture such as sand
which could lead to offsite movement in the instance of sandy soils.
✔✔Describe how organic matter affects herbicide movement in the soil. - ✔✔Herbicides
tend to stick to organic matter tightly so it makes herbicide applications into the soil
difficult to move.
✔✔Describe how time to next irrigation affects herbicide movement in the soil. -
✔✔Some herbicides are leached with irrigation or activated with water, but if the
irrigation event is too close to an application it could also lead to runoff and excessive
leaching.
✔✔Describe how pH affects herbicide movement in the soil. - ✔✔Below pH 6 herbicides
will bind tightly with soil colloids and potentially breakdown.
✔✔Define pesticide drift and describe some of the harmful consequences. - ✔✔Drift is
offsite movement of pesticide application particles. It can lead to plant damage, crop
rejection, and damage to wildlife.
✔✔Describe methods to manage pesticide drift. - ✔✔Applications during favorable
weather conditions, adjuvants, spraying close to the canopy
✔✔Chemigation - ✔✔Applying a pesticide through water, used in fumigants
✔✔Wick/Wiper application - ✔✔Selective application of herbicides to weeds growing
taller than the crop.
✔✔Incorporation application - ✔✔Mix pesticide into soil with machine tillage, irrigation,
or rain. Used with preplant and preemergent pesticides.
SOLUTIONS SCORED A+
✔✔Dry flowable (DF), dispersible granule (DG), water dispersible granule (WDG) -
✔✔Form suspension, requires agitation, flow easily out of container to reduce dust
problem WP have
✔✔Aqueous solution (AS), flowable (F), liquid flowable (L) - ✔✔Liquid formulation
requiring agitation in a spray tank
✔✔Emulsifiable concentrate (E or EC) - ✔✔For AI with low water solubility. Forms an
emulsion in water
✔✔Soluble concentrate (S, SC), soluble powder (SP), water-soluble concentrate (WSC)
- ✔✔Low volatility, not abrasive, form a solution in tank, do not require agitation
✔✔List reasons for adding an adjuvant to an herbicide formulation. - ✔✔To enhance or
modify the solution. Enhance the emulsifying, dispersing, spreading, sticking, or wetting
properties of liquids. Reduce runoff, uniform spread
✔✔Describe soil conditions that enhance the degradation of herbicides. - ✔✔Microbial
activities, pH below 6, light absorption, water
✔✔Describe soil conditions that increase the persistence or availability of soil applied
herbicides. - ✔✔Soil type, soil temperature, management practices, application method
✔✔Biotype - ✔✔organisms/structures with same genetic makeup resulting in similarity
in appearance
✔✔Ecotype - ✔✔a population adapted to its unique local environmental conditions
✔✔Describe the impact of weed biotypes on herbicide resistance. - ✔✔Weed biotypes
can lead to an entire group of weeds developing resistance to an herbicide because of
the identical genetic makeup
✔✔Describe how knowledge of the herbicide mode of action/group number aids in
resistance management. - ✔✔Rotating between different modes of action can reduce
the possibility of a weed developing resistance to a particular mode of action.
✔✔Differentiate between herbicide tolerance and herbicide resistance in weeds. -
✔✔Herbicide tolerance is ability of a weed to tolerate an herbicide due to a physical
feature, whereas resistance is genetic coding that enables a weed to completely resist
an herbicide.
, ✔✔Describe methods used to prevent and manage pesticide resistance. - ✔✔Rotating
to herbicides with different modes of action, using non-chemical controls, crop rotations,
etc.
✔✔Describe the importance of crop rotation in managing herbicide resistance -
✔✔Weeds may be crop specific, so rotation can help reduce weed pressure and reduce
the amount of weeds that out compete a particular crop
✔✔Describe how herbicide solubility affects herbicide movement in the soil. - ✔✔Water
soluble herbicides move easier with water than those that are not soluble.
✔✔Describe how soil texture affects herbicide movement in the soil. - ✔✔Some
textures, such as clay, will hold onto herbicides more tightly than a texture such as sand
which could lead to offsite movement in the instance of sandy soils.
✔✔Describe how organic matter affects herbicide movement in the soil. - ✔✔Herbicides
tend to stick to organic matter tightly so it makes herbicide applications into the soil
difficult to move.
✔✔Describe how time to next irrigation affects herbicide movement in the soil. -
✔✔Some herbicides are leached with irrigation or activated with water, but if the
irrigation event is too close to an application it could also lead to runoff and excessive
leaching.
✔✔Describe how pH affects herbicide movement in the soil. - ✔✔Below pH 6 herbicides
will bind tightly with soil colloids and potentially breakdown.
✔✔Define pesticide drift and describe some of the harmful consequences. - ✔✔Drift is
offsite movement of pesticide application particles. It can lead to plant damage, crop
rejection, and damage to wildlife.
✔✔Describe methods to manage pesticide drift. - ✔✔Applications during favorable
weather conditions, adjuvants, spraying close to the canopy
✔✔Chemigation - ✔✔Applying a pesticide through water, used in fumigants
✔✔Wick/Wiper application - ✔✔Selective application of herbicides to weeds growing
taller than the crop.
✔✔Incorporation application - ✔✔Mix pesticide into soil with machine tillage, irrigation,
or rain. Used with preplant and preemergent pesticides.
