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Ohio Pesticide Applicator Certification: Category 6a –
Ornamental Weed Control Questions and Correct Answers
Plus Rationales 2025
- What is the primary goal of ornamental weed control? A. Increase turfgrass density B. Promote flowering C. Prevent weed competition D. Enhance soil compaction Preventing weed competition ensures that ornamental plants can thrive without being crowded or outcompeted for light, nutrients, and water.
- Which weed type typically reappears every year from seed? A. Perennial B. Biennial C. Annual D. Invasive Annual weeds complete their life cycle in one season and must regrow from seed each year.
- A biennial weed completes its life cycle in how long?
A. 1 year B. 2 years C. 3 years D. Indefinitely Biennial weeds grow vegetatively the first year and flower, set seed, and die in the second.
- Which is an example of a perennial weed? A. Crabgrass B. Dandelion C. Chickweed D. Lambsquarters Dandelions have deep taproots and return yearly from root systems.
- What is the most effective time to apply pre-emergent herbicides? A. After weeds have emerged B. During winter C. Before weed seeds germinate D. During flowering Pre-emergent herbicides prevent seeds from germinating, so timing before seed germination is crucial.
- Which part of the plant do systemic herbicides travel through?
- Non-selective herbicides are typically used for: A. Lawns B. Total vegetation control C. Mulch beds D. Water features Non-selective herbicides kill nearly all plant types and are used for complete vegetation removal. 10.Which method improves post-emergent herbicide uptake? A. Waiting until leaves dry B. Applying in cold temperatures C. Using a surfactant D. Adding fertilizer Surfactants help the herbicide stick and spread on the leaf surface for better absorption. 11.What is glyphosate classified as? A. Selective herbicide B. Non-selective systemic herbicide C. Fungicide D. Contact herbicide Glyphosate is a widely used non-selective systemic herbicide absorbed through foliage.
12.Which is most important when spraying ornamentals near turf? A. Wind direction B. Soil temperature C. Herbicide selectivity D. Irrigation pressure Using a selective herbicide is crucial to avoid damaging ornamental plants or turf. 13.What is the function of the label signal word “CAUTION”? A. Extremely toxic B. Slightly toxic C. Highly toxic D. Not toxic "CAUTION" is used on products that are slightly toxic or pose minimal hazard. 14.Drift can be reduced by: A. Increasing nozzle pressure B. Using low-drift nozzles C. Applying during wind D. Using smaller droplets Low-drift nozzles reduce the amount of herbicide that becomes airborne.
18.Yellow nutsedge is best controlled with: A. Broadleaf herbicide B. Sedge-specific herbicide C. Fungicide D. Fertilizer Sedges require specific herbicides, such as halosulfuron or sulfentrazone. 19.The active ingredient in a herbicide is: A. The diluent B. The chemical that kills weeds C. The filler D. The inert ingredient The active ingredient is the component that targets and kills the weed. 20.What is the Ohio pesticide license renewal cycle? A. 1 year B. 3 months C. 3 years D. 6 years Ohio applicator licenses must be renewed every three years.
21.Drift is more likely under which conditions? A. Calm, cool days B. Hot, windy conditions C. During rain D. Cloudy weather Wind and heat increase the likelihood of fine droplets drifting off-target. 22.Weed identification is important because: A. It helps choose sprayers B. Herbicides vary in effectiveness by weed C. Labels are irrelevant D. All weeds respond the same Knowing the weed species helps select the right herbicide and timing. 23.A herbicide with a “Danger” signal word means: A. Slightly toxic B. Highly toxic C. Non-toxic D. Not for professional use "Danger" indicates a high level of toxicity and requires extra care. 24.The re-entry interval (REI) is:
27.When using granular herbicides, the most important factor for effectiveness is: A. Leaf wetness B. Soil moisture C. Wind speed D. Humidity Granular herbicides must be activated by moisture, often through irrigation or rainfall. 28.A surfactant is added to spray solutions to: A. Reduce herbicide toxicity B. Improve herbicide coverage and uptake C. Reduce odor D. Improve root absorption Surfactants help the herbicide stick to and penetrate plant surfaces. 29.Post-emergent herbicides work best when: A. Applied in winter B. Weeds are young and actively growing C. Soil is dry D. Rain is expected soon Young, actively growing weeds absorb herbicide more effectively, leading to better control.
30.A perennial weed in ornamentals is: A. Pigweed B. Canada thistle C. Goosegrass D. Spurge Canada thistle is a tough perennial weed that regrows from underground parts. 31.A restricted-use pesticide (RUP) requires: A. College degree B. Homeowner license C. Certified applicator status D. Organic approval RUPs can only be applied by certified applicators due to their higher potential for harm. 32.Tank mixing refers to: A. Mixing fuel with herbicide B. Combining multiple pesticides in one spray tank C. Cleaning a spray tank D. Filling a backpack sprayer Tank mixing combines herbicides (or other chemicals) to control multiple weed types in one application.
36.The label is considered: A. A suggestion B. Optional for professionals C. A legal document D. Just marketing material The label is legally enforceable and must be followed to comply with state and federal laws. 37.How often must Ohio commercial applicators recertify? A. Every 6 months B. Every year C. Every 3 years D. Every 5 years Ohio applicators must recertify every three years through continuing education or retesting. 38.Ornamental beds are best treated with: A. Soil sterilants B. Fertilizer only C. Selective pre- and post-emergent herbicides D. Fungicides
Combination treatments with selective herbicides minimize damage to ornamentals while controlling weeds. 39.What is leaching in herbicide context? A. Evaporation of herbicide B. Downward movement of herbicide through soil C. Weeds spreading underground D. Photodegradation Leaching can carry herbicides beyond their target area, potentially harming nearby plants or water sources. 40.A good time to apply pre-emergents in Ohio is: A. After first frost B. Early spring, before weed seeds germinate C. Midsummer D. Late fall Applying pre-emergents in early spring prevents annual weeds from establishing. 41.The best way to calibrate your sprayer is: A. By sight B. By feel
A. Weeds are stronger B. Plants need rest C. Increased risk of phytotoxicity D. Wind is higher at night High temperatures can cause herbicides to volatilize or damage sensitive ornamental plants. 45.What does “spot treatment” mean? A. Treating entire fields B. Applying herbicide only where weeds are present C. Painting weeds D. Using mulch Spot treatments focus herbicide use where needed, reducing cost and non- target damage. 46.Ohio applicators are regulated by: A. Department of Transportation B. USDA C. Ohio Department of Agriculture (ODA) D. EPA only The Ohio Department of Agriculture oversees pesticide applicator certification and enforcement.
47.Which of these can reduce herbicide performance? A. Using surfactants B. Warm weather C. Low water pH or poor mixing D. Applying on cloudy days Poor mixing or incompatible water pH can reduce herbicide effectiveness. 48.Overapplication of herbicide can lead to: A. Faster weed growth B. Environmental contamination and plant damage C. Improved ornamental growth D. Resistance elimination Too much herbicide can damage non-target plants, contaminate soil and water, and violate regulations. 49.A “pre-harvest interval” applies mostly to: A. Ornamentals B. Edible crops C. Turf D. Mulch areas Pre-harvest intervals are waiting periods after pesticide application before harvesting crops.
53.What is the "weed threshold"? A. Total plant weight B. The number of weeds before action is taken C. Soil pH D. Wind speed for drift The weed threshold is the point at which weed populations cause unacceptable damage or cost. 54.The main disadvantage of contact herbicides is: A. Too strong B. They don’t kill roots C. Over-regulated D. Require fertilizers Contact herbicides only kill the visible part of the plant, not the root system. 55.Which is an annual grass weed? A. Dandelion B. Crabgrass C. Plantain D. Oxalis Crabgrass germinates from seed each year and is a common annual grassy weed.
56.What label section explains how to avoid resistance? A. Directions for Use B. Resistance Management C. Environmental Hazards D. Warranty Statement The resistance management section explains how to rotate modes of action and prevent resistance. 57.What is volatilization? A. Spray runoff B. Herbicide turning into gas and drifting C. Soil absorption D. Tank mixing error Volatile herbicides can vaporize under hot conditions and move off-target. 58.What is the primary concern when using herbicide near water? A. Weeds returning B. Water contamination C. Drift onto turf D. Fertilizer leaching Contaminating water sources can harm aquatic life and violate environmental regulations.
