Iowa Commercial Pesticide Applicator Category 1A Questions with Correct Answer Rated A+ 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 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 1 / 2
Define photodecomposition - Correct Answer Chemical breakdown caused by exposure to light Name two herbicides that must be incorporated to prevent photodecomposition. - Correct Answer Treflan, Sonalan Why are Basagran, Blazer, Buctril, Poast Plus, and Fusilade 2000 only applied postemergence? - Correct Answer They have little or no soil activity Are Roundup and Gramoxone Extra selective or nonselective herbicides? - Correct Answer Nonselective Are Blazer, Basagran, Buctril, and Gramoxone Extra contact herbicides or translocated herbicides? - Correct Answer Contact herbicides Define translocated herbicides - Correct Answer Herbicides which move in the phloem of plants Do translocated herbicides move up, down, or both ways in plants? - Correct Answer Because translocated herbicides move within the phloem, they can move both up and down a plant.Are Roundup, 2,4-D, Fusilade 2000, Poast Plus, Clarity, and Banvil contact herbicides or translocted herbicides? - Correct Answer Translocated herbicides What is essential when using contact herbicides? - Correct Answer Good spray coverage (usually involving high carrier volumes) When is the best time (in regards to maximum weed control) to apply contact herbicides to annual weeds? - Correct Answer When the weeds are small and actively growing Why are contact herbicides not great at controlling perennial weeds? - Correct Answer They only control the shoot, and cannot travel down to kill the root system resulting in regrowth
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