Iowa Commercial Pesticide Applicator Category 1A exam with 100% correct answers

What is the greatest hazard when applying most herbicides? Injury to nontarget plants Name some herbicides which are very effective against germinating weeds but less effective on established weeds. Frontier, Lasso, and Dual 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 Two herbicides which are more active on soils with a pH above 7.5 and can injure soybeans Sencor and Lexone Where are high pH soils most common in Iowa? Next to limestone and gravel roads Two herbicides that are more persistent and likely to carryover residues. Atrazine and chlorimuron What factors can increase chances of herbicide carryover? 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? Yes What do preemergence herbicides rely on to move the herbicide into the weed seed germination zone (top 1/2-1 inch) of soil? Rainfall or irrigation What tillage tools will improve weed control when rainfall does not occur soon after herbicide application, and weeds begin emerging? Rotary Hoe and Harrow Name 3 herbicides which must be incorporated to prevent evaporation loss. Sultan+, Eradicane, Eradicane Extra Define photodecomposition Chemical breakdown caused by exposure to light Name two herbicides that must be incorporated to prevent photodecomposition. Treflan, Sonalan Why are Basagran, Blazer, Buctril, Poast Plus, and Fusilade 2000 only applied postemergence? They have little or no soil activity Are Roundup and Gramoxone Extra selective or nonselective herbicides? Nonselective Are Blazer, Basagran, Buctril, and Gramoxone Extra contact herbicides or translocated herbicides? Contact herbicides Define translocated herbicides Herbicides which move in the phloem of plants Do translocated herbicides move up, down, or both ways in plants? 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? Translocated herbicides What is essential when using contact herbicides? 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? When the weeds are small and actively growing Why are contact herbicides not great at controlling perennial weeds? They only control the shoot, and cannot travel down to kill the root system resulting in regrowth When you are using translocated herbicides to control perennial weed root systems, when is usually the best treatment time? Bud to bloom growth stage When applying Prowl, Banvel, and Clarity in a corn crop, what practice can cause injury Incorporation Why shouldn't you apply 2,4-D to corn from tasseling to brown silk? Severe pollination injury can occur When does particle drift occur? Small spray droplets move off target when they are applied, typically due to wind How can you reduce particle drift? Use coarse sprays and drift control agents while avoiding application during windy conditions Which formulation of 2,4-D can drift in vapor form and which cannot? Ester 2,4-D can vapor drift