IOWA COMMERCIAL PESTICIDE
APPLICATOR CATEGORY 1A
QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS 100%
CORRECT RATED A+ NEWLY
UPDATED 2025
Q1: What is the greatest hazard when applying most herbicides?
✔ Injury to nontarget plants
Explanation: Herbicides are designed to kill plants—so drift or misapplication
can easily harm crops, lawns, trees, or ornamental plants not intended to be treated.
Q2: Name some herbicides which are very effective against germinating weeds
but less effective on established weeds.
✔ Frontier, Lasso, and Dual
Explanation: These are pre-emergent herbicides effective on germinating
seeds, but not strong enough for mature weeds.
Q3: What soil conditions reduce the activity of many herbicides and require
increased rates for adequate weed control?
✔ Higher levels of soil organic matter or clay
Explanation: These soil types bind herbicides, reducing their availability to
control weeds—requiring higher application rates.
Q4: Name two herbicides which are more active on soils with a pH above 7.5
and can injure soybeans.
, ✔ Sencor and Lexone
Explanation: On high pH soils, these herbicides increase in solubility and
uptake, leading to potential soybean injury.
Q5: Where are high pH soils most common in Iowa?
✔ Next to limestone and gravel roads
Explanation: Limestone and gravel materials raise soil alkalinity (pH), which
affects herbicide behavior.
Q6: Name two herbicides that are more persistent and likely to carry over
residues.
✔ Atrazine and Chlorimuron
Explanation: These herbicides degrade slowly and may persist in soil, impacting
subsequent crops (carryover).
What factors can increase chances of herbicide carryover? - 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? - 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? - ANSWER✔✔Rainfall or irrigation
What tillage tools will improve weed control when rainfall does not occur soon
after herbicide application, and weeds begin emerging? - ANSWER✔✔Rotary Hoe
and Harrow
APPLICATOR CATEGORY 1A
QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS 100%
CORRECT RATED A+ NEWLY
UPDATED 2025
Q1: What is the greatest hazard when applying most herbicides?
✔ Injury to nontarget plants
Explanation: Herbicides are designed to kill plants—so drift or misapplication
can easily harm crops, lawns, trees, or ornamental plants not intended to be treated.
Q2: Name some herbicides which are very effective against germinating weeds
but less effective on established weeds.
✔ Frontier, Lasso, and Dual
Explanation: These are pre-emergent herbicides effective on germinating
seeds, but not strong enough for mature weeds.
Q3: What soil conditions reduce the activity of many herbicides and require
increased rates for adequate weed control?
✔ Higher levels of soil organic matter or clay
Explanation: These soil types bind herbicides, reducing their availability to
control weeds—requiring higher application rates.
Q4: Name two herbicides which are more active on soils with a pH above 7.5
and can injure soybeans.
, ✔ Sencor and Lexone
Explanation: On high pH soils, these herbicides increase in solubility and
uptake, leading to potential soybean injury.
Q5: Where are high pH soils most common in Iowa?
✔ Next to limestone and gravel roads
Explanation: Limestone and gravel materials raise soil alkalinity (pH), which
affects herbicide behavior.
Q6: Name two herbicides that are more persistent and likely to carry over
residues.
✔ Atrazine and Chlorimuron
Explanation: These herbicides degrade slowly and may persist in soil, impacting
subsequent crops (carryover).
What factors can increase chances of herbicide carryover? - 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? - 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? - ANSWER✔✔Rainfall or irrigation
What tillage tools will improve weed control when rainfall does not occur soon
after herbicide application, and weeds begin emerging? - ANSWER✔✔Rotary Hoe
and Harrow
