# GTBOP Moodle Quiz
## Weed Control in Ornamentals for the Nursery and Landscape — Dr. Chris Marble

**Webinar Date:** July 13, 2023
**Speaker:** Dr. Chris Marble, University of Florida
**Series:** Green & Commercial
**Source Documents:** Corrected SRT (618 blocks) + Archive Package (Stage 2)

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### Question 1
**Timestamp Reference:** 1:36 – 3:54
**Difficulty:** Recall

According to Dr. Marble, what is the number one reason herbicides fail or cause plant injury when a labeled product is being used?

a) Herbicide resistance in the weed population
b) Applying during unfavorable weather conditions
c) Poor calibration and application practices
d) Using an expired herbicide product

**Correct Answer:** c
**Explanation:** Dr. Marble identified poor calibration and application practices as the number one reason herbicides fail, noting that some applicators were off by 50 to several hundred percent of the target rate during field measurements.
**Source in transcript:** Blocks 28–56, ~1:36–3:54

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### Question 2
**Timestamp Reference:** 4:00 – 4:28
**Difficulty:** Recall

When Dr. Marble's team measured applicator accuracy at multiple Southeast locations, what percentage range did most people fall within of the target rate?

a) Within 1–5 percent
b) Within 10–20 percent
c) Within 30–40 percent
d) Within 50–60 percent

**Correct Answer:** b
**Explanation:** Marble reported that most people were within 10 to 20 percent of the label rate, which he considered a good real-world result. However, some were off by a quarter of the rate or more.
**Source in transcript:** Blocks 59–63, ~4:00–4:28

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### Question 3
**Timestamp Reference:** 6:35 – 7:46
**Difficulty:** Application

A nursery manager has just potted a new crop of woody ornamentals. When should pre-emergent herbicides first be applied?

a) Immediately at potting before watering in
b) After the plants are watered in and the soil has settled
c) Two weeks after potting to allow root establishment
d) Only after the first weeds appear in the containers

**Correct Answer:** b
**Explanation:** Marble explained that in a nursery situation, pre-emergent herbicides are typically applied after potting once plants have been watered in and the soil is settled, to prevent exposed roots from contacting the herbicide.
**Source in transcript:** Blocks 85–91, ~6:35–7:24

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### Question 4
**Timestamp Reference:** 8:20 – 9:28
**Difficulty:** Application

A landscape applicator plans to apply a pre-emergent herbicide over the top of ornamentals during a hot afternoon when plants are actively producing new growth. What is the most likely concern?

a) The herbicide will break down too quickly in the heat
b) Tender new growth is more susceptible to herbicide injury
c) Pre-emergent herbicides are ineffective at high temperatures
d) The soil will be too dry for proper herbicide activation

**Correct Answer:** b
**Explanation:** Marble stressed that plants are most susceptible to injury during bud swell and when young foliage is developing, and that high temperatures further increase the risk of injury from over-the-top pre-emergent applications.
**Source in transcript:** Blocks 104–113, ~8:20–9:28

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### Question 5
**Timestamp Reference:** 11:30 – 13:17
**Difficulty:** Recall

Which of the following environmental conditions does Dr. Marble say can reduce post-emergence herbicide performance?

a) Several days of cloudy, overcast weather after application
b) Applying to weeds during a period of rapid active growth
c) High relative humidity at the time of application
d) Applying in the early morning on a clear day

**Correct Answer:** a
**Explanation:** Marble stated that cloudy, overcast conditions for several days after application can delay or reduce the effects of post-emergence herbicides and reduce efficacy. He noted that applications on clear, sunny mornings tend to be more effective.
**Source in transcript:** Blocks 147–148, ~12:21–12:43

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### Question 6
**Timestamp Reference:** 13:18 – 14:24
**Difficulty:** Application

A lawn care operator mows a landscape bed area and then immediately applies a systemic post-emergence herbicide to the remaining weed stems. What problem is most likely to occur?

a) The herbicide will damage the surrounding ornamental plants
b) The mowing removed leaf tissue needed for herbicide uptake and translocation
c) The herbicide will be more effective because weeds are stressed
d) Soil disturbance from mowing will activate weed seeds

**Correct Answer:** b
**Explanation:** Marble explained that mowing soon before or after a post-emergence application can reduce efficacy because it removes the majority of the weed's leaf tissue, puts the weed into a semi-state of stress, and limits the herbicide's ability to translocate down to the roots for thorough control.
**Source in transcript:** Blocks 165–171, ~13:57–14:25

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### Question 7
**Timestamp Reference:** 14:28 – 15:35
**Difficulty:** Recall

Dr. Marble ranked several factors that impact post-emergence herbicide performance. Which factor did he rank as MOST important?

a) Time of day of application
b) Adjuvant or surfactant selection
c) Rate and inherent efficacy of the herbicide on the target weed
d) Environmental conditions at the time of application

**Correct Answer:** c
**Explanation:** Marble ranked the rate and efficacy of the herbicide on the target weed as the most important factor, reasoning that if the herbicide doesn't work on that weed species, optimal environmental conditions or adjuvants won't compensate. Weed size ranked second, followed by environmental conditions, adjuvants, and time of day.
**Source in transcript:** Blocks 172–186, ~14:28–15:35

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### Question 8
**Timestamp Reference:** 17:17 – 18:43
**Difficulty:** Analysis

A nursery used Gallery (isoxaben) exclusively for several years to control bittercress. They now have a severe crabgrass infestation. Based on Dr. Marble's presentation, what is the most likely explanation?

a) The crabgrass developed resistance to Gallery
b) Gallery is only effective on broadleaf weeds, allowing grass species to proliferate unchecked
c) Gallery's residual activity decreased over time due to soil buildup
d) Bittercress seeds were contaminated with crabgrass seed

**Correct Answer:** b
**Explanation:** Marble used this exact example to illustrate why herbicide rotation matters. Gallery is only effective on broadleaves, so when the nursery used it exclusively, grass species were not controlled and their populations increased exponentially, eventually becoming a major problem.
**Source in transcript:** Blocks 205–219, ~17:33–18:44

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### Question 9
**Timestamp Reference:** 18:48 – 25:10
**Difficulty:** Recall

In Dr. Marble's three-step process for choosing herbicides, what is the correct order of steps?

a) Identify target weeds → select the cheapest option → apply at the highest labeled rate
b) Determine what is labeled/safe for the ornamental → identify the target weed species → combine selections into a rotation plan
c) Choose a mode of action group → find products in that group → check the ornamental safety label
d) Identify the primary weed species → apply the most effective herbicide → rotate only if resistance develops

**Correct Answer:** b
**Explanation:** Marble outlined three steps: first, determine which herbicides are labeled and safe for the ornamental species; second, identify the primary and secondary weed species by season; third, combine those into a year-round rotation using different modes of action.
**Source in transcript:** Blocks 220–308, ~18:48–25:20

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### Question 10
**Timestamp Reference:** 23:01 – 25:06
**Difficulty:** Application

When selecting a pre-emergent herbicide using the efficacy charts Dr. Marble referenced, what rating should you look for on your PRIMARY weed species?

a) Any rating, as long as the herbicide is labeled for the ornamental
b) Fair (F) or better
c) Good (G)
d) It does not matter as long as the secondary species rating is good

**Correct Answer:** c
**Explanation:** Marble explained that for the primary weed species — the most important weed to control — you want a herbicide rated "good" (G) on the efficacy chart. For secondary species, a rating of "fair" (F) or better is acceptable.
**Source in transcript:** Blocks 280–302, ~23:32–24:59

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### Question 11
**Timestamp Reference:** 27:34 – 31:06
**Difficulty:** Recall

In Dr. Marble's research comparing post-only versus pre-plus-post herbicide programs, by what percentage range was total herbicide active ingredient reduced when pre-emergent herbicides were included?

a) 10 to 20 percent
b) 20 to 30 percent
c) 40 to 60 percent
d) 70 to 80 percent

**Correct Answer:** c
**Explanation:** Marble's research showed that including pre-emergent herbicides like Specticle or SureGuard with post-emergence treatments reduced the total amount of herbicide active ingredient applied by 40 to 60 percent compared to using glyphosate or other post-emergence herbicides alone.
**Source in transcript:** Blocks 356–358, ~30:27–31:06

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### Question 12
**Timestamp Reference:** 37:01 – 38:05
**Difficulty:** Analysis

Dr. Marble discussed the increasing restrictions on glyphosate use in certain counties and by HOAs in Florida. Based on his presentation, why is it important to have alternatives to glyphosate even if your sites have no restrictions on its use?

a) Glyphosate is more expensive than alternative products
b) Over-reliance on any single herbicide contributes to resistance development
c) Glyphosate is no longer available for commercial purchase
d) Alternative products provide faster visual results for clients

**Correct Answer:** b
**Explanation:** Marble stated that the reason there are many glyphosate-resistant weeds is because it has been overused without enough rotation between different modes of action. He emphasized that professionals need alternatives regardless of restrictions, to prevent further resistance development.
**Source in transcript:** Blocks 455–459, ~37:53–38:06

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### Question 13
**Timestamp Reference:** 38:08 – 39:00
**Difficulty:** Recall

What is the primary limitation of glufosinate (Finale/Cheetah) compared to glyphosate as a post-emergence herbicide?

a) It can only be used on grasses, not broadleaves
b) It is primarily contact-acting and doesn't provide the same systemic control
c) It requires a restricted-use pesticide license to purchase
d) It cannot be used in landscape planting beds

**Correct Answer:** b
**Explanation:** Marble described glufosinate as similar to glyphosate in its broad-spectrum activity on broadleaves, grasses, and sedges, but noted that it is primarily contact action, meaning it doesn't translocate systemically through the plant the way glyphosate does.
**Source in transcript:** Blocks 460–467, ~38:08–38:34

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### Question 14
**Timestamp Reference:** 42:23 – 43:50
**Difficulty:** Application

A landscape professional needs to control bermudagrass growing into a bed of azaleas and roses. Based on Dr. Marble's presentation, which type of selective herbicide would be the safest option for over-the-top application?

a) A PPO-inhibiting pre-emergent herbicide
b) A glufosinate-based non-selective spray, applied carefully
c) A graminicide such as sethoxydim, clethodim, fluazifop, or fenoxaprop
d) Basagran (bentazon) applied as a directed spray

**Correct Answer:** c
**Explanation:** Marble highlighted graminicides as underutilized tools that can be applied over the top of hundreds of broadleaf ornamental species. They affect only true grasses and are much safer than spot-treating with non-selective herbicides like glyphosate, which risks damaging the ornamentals.
**Source in transcript:** Blocks 514–531, ~42:23–43:50

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### Question 15
**Timestamp Reference:** 45:52 – 47:59
**Difficulty:** Recall

What are the three signal word levels on pesticide labels, listed from lowest to highest toxicity?

a) Caution, Warning, Danger/Poison
b) Notice, Caution, Danger
c) Warning, Caution, Restricted
d) Low, Moderate, High

**Correct Answer:** a
**Explanation:** During the Q&A, Marble reviewed the three signal word levels: caution (lowest), warning (intermediate), and danger/poison (most dangerous). He noted these are based on different routes of toxicity including skin and eye exposure, and that higher signal words require more PPE and may carry restricted-use designations.
**Source in transcript:** Blocks 575–587, ~46:51–48:02

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## Quiz Summary

| Difficulty | Count | Percentage |
|------------|:-----:|:----------:|
| Recall | 8 | 53% |
| Application | 5 | 33% |
| Analysis | 2 | 13% |

**Coverage distribution:**
- Early (0:00–17:00): Questions 1–7
- Middle (17:00–35:00): Questions 8–11
- Late (35:00–50:38): Questions 12–15

**Source document:** Corrected SRT — GTBOP_Transcript_2023-07-13_WeedControlOrnamentals.srt (618 blocks)

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*Generated for UGA Center for Urban Agriculture / GTBOP Moodle Certificate Courses*
