1
IOWA COMMERCIAL PESTICIDE
APPLICATOR CATEGORY 1A
QUESTIONS & SOLUTIONS
2026/2027
What is the greatest hazard when applying most herbicides? - correct-answer -
Injury to nontarget plants
Name some herbicides which are very effective against germinating weeds but
less effective on established weeds. - correct-answer -Frontier, Lasso, and Dual
What soil conditions reduce the activity of many herbicides and require increased
rates for adequate weed control? - correct-answer -Higher levels of soil organic
matter or clay
Two herbicides which are more active on soils with a pH above 7.5 and can injure
soybeans - correct-answer -Sencor and Lexone
Where are high pH soils most common in Iowa? - correct-answer -Next to
limestone and gravel roads
, 2
Two herbicides that are more persistent and likely to carryover residues. -
correct-answer -Atrazine and chlorimuron
What factors can increase chances of herbicide carryover? - correct-answer -Dry
weather, high rates, late application, and in the case of some herbicides, high soil
pH
Can additive injury occur when applying Sencor/Lexone on soybeans in fields with
atrazine carryover residues? - correct-answer -Yes
What do preemergence herbicides rely on to move the herbicide into the weed
seed germination zone (top 1/2-1 inch) of soil? - correct-answer -Rainfall or
irrigation
What tillage tools will improve weed control when rainfall does not occur soon
after herbicide application, and weeds begin emerging? - correct-answer -Rotary
Hoe and Harrow
Name 3 herbicides which must be incorporated to prevent evaporation loss. -
correct-answer -Sultan+, Eradicane, Eradicane Extra
Define photodecomposition - correct-answer -Chemical breakdown caused by
exposure to light
IOWA COMMERCIAL PESTICIDE
APPLICATOR CATEGORY 1A
QUESTIONS & SOLUTIONS
2026/2027
What is the greatest hazard when applying most herbicides? - correct-answer -
Injury to nontarget plants
Name some herbicides which are very effective against germinating weeds but
less effective on established weeds. - correct-answer -Frontier, Lasso, and Dual
What soil conditions reduce the activity of many herbicides and require increased
rates for adequate weed control? - correct-answer -Higher levels of soil organic
matter or clay
Two herbicides which are more active on soils with a pH above 7.5 and can injure
soybeans - correct-answer -Sencor and Lexone
Where are high pH soils most common in Iowa? - correct-answer -Next to
limestone and gravel roads
, 2
Two herbicides that are more persistent and likely to carryover residues. -
correct-answer -Atrazine and chlorimuron
What factors can increase chances of herbicide carryover? - correct-answer -Dry
weather, high rates, late application, and in the case of some herbicides, high soil
pH
Can additive injury occur when applying Sencor/Lexone on soybeans in fields with
atrazine carryover residues? - correct-answer -Yes
What do preemergence herbicides rely on to move the herbicide into the weed
seed germination zone (top 1/2-1 inch) of soil? - correct-answer -Rainfall or
irrigation
What tillage tools will improve weed control when rainfall does not occur soon
after herbicide application, and weeds begin emerging? - correct-answer -Rotary
Hoe and Harrow
Name 3 herbicides which must be incorporated to prevent evaporation loss. -
correct-answer -Sultan+, Eradicane, Eradicane Extra
Define photodecomposition - correct-answer -Chemical breakdown caused by
exposure to light
