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

**Webinar Date:** July 13, 2023
**Speaker:** Dr. Chris Marble, Associate Professor, University of Florida Mid-Florida Research and Education Center
**Series:** Green & Commercial
**Duration:** 50:38

**Activity Type:** Timestamp-Linked Review Prompts
**Source:** Corrected SRT (Stage 1) — `GTBOP_Transcript_2023-07-13_WeedControlOrnamentals.srt` (618 blocks)

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### Review Task 1
**Watch:** 1:36 – 6:34
**Task:** Identify the number one reason herbicides fail according to Dr. Marble, and describe the range of rate errors his team measured at Southeast nursery and landscape operations.
**Key Points to Identify:**
- Poor calibration as the primary cause of both poor weed control and plant injury
- Most applicators were within 10–20% of label rate, but some were off by 50% to several hundred percent
- Free UF-developed calibration tools and herbicide mixing calculators available for download

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### Review Task 2
**Watch:** 6:35 – 10:42
**Task:** Explain why the timing of pre-emergent herbicide applications over the top of ornamentals matters, and describe the holly/SureGuard example that illustrates the difference between new growth and hardened foliage.
**Key Points to Identify:**
- Avoid application during bud swell, tender new growth, or high-temperature periods
- In the SureGuard (flumioxazin) trial, newest growth was severely affected while older hardened foliage showed no injury
- Plants with fully expanded, matured leaves are less susceptible to injury from over-the-top pre-emergent applications

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### Review Task 3
**Watch:** 10:42 – 15:38
**Task:** List the factors Dr. Marble ranks in order of importance for post-emergence herbicide performance, from most to least important.
**Key Points to Identify:**
- Rate and inherent efficacy of the herbicide (most important)
- Size of the weed at time of application
- Environmental conditions (temperature, relative humidity)
- Adjuvant/surfactant selection
- Time of day (least important)

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### Review Task 4
**Watch:** 15:38 – 19:17
**Task:** Describe the Gallery/crabgrass example and explain why Dr. Marble says you need a "program, not products."
**Key Points to Identify:**
- A nursery switched to Gallery (isoxaben) exclusively for bittercress control; it worked well on bittercress but had no activity on grasses
- Crabgrass population exploded because no herbicide in the rotation targeted grassy species
- No single herbicide controls all weeds; the uncontrolled species increases exponentially
- A program is a planned but flexible schedule rotating herbicides across modes of action, combined with cultural controls

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### Review Task 5
**Watch:** 19:17 – 26:08
**Task:** Walk through Dr. Marble's three-step herbicide selection process using his container-grown gardenia example. For each step, identify what decision is being made.
**Key Points to Identify:**
- Step 1: Determine which herbicides are labeled and safe for the ornamental (gardenia) — narrows to granular options using the 2017 Southeast Pest Control Guide
- Step 2: Identify primary weed species (spotted spurge) and secondary species (eclipta) by season; select herbicides rated "Good" for the primary and at least "Fair" for the secondary
- Step 3: Combine selected herbicides into a year-round rotation using different mode-of-action groups to avoid resistance

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### Review Task 6
**Watch:** 27:52 – 31:17
**Task:** Summarize the research results comparing post-emergence-only programs to combined pre+post-emergence programs in landscape beds. Note the specific metrics Dr. Marble reports.
**Key Points to Identify:**
- Study compared Ranger (glyphosate), Finale (glufosinate), and Reward (diquat) alone versus combined with Specticle or SureGuard
- Glyphosate-only required retreatment basically every month; combined programs needed only 1–2 follow-up applications
- Including pre-emergent herbicides reduced total costs by 3–30% and reduced total herbicide active ingredient by 40–60%

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### Review Task 7
**Watch:** 37:01 – 42:05
**Task:** Compare glyphosate alternatives as post-emergence non-selective herbicides. Describe how desiccant-type products differ from systemic herbicides in terms of performance over time.
**Key Points to Identify:**
- Glufosinate (Finale/Cheetah) is the most common alternative — broad-spectrum but primarily contact action, less systemic than glyphosate
- Desiccant products (Axxe, Finalsan, FireWorxx, acetic acid) show rapid burndown (visible within 30 minutes) but are not translocated
- At 2 weeks, burndown is impressive; by 4–8 weeks, larger weeds recover because coverage doesn't reach the base
- Two applications of desiccants can achieve control comparable to one glyphosate application on annuals; large perennials require many more

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### Review Task 8
**Watch:** 42:23 – 44:44
**Task:** Identify the selective post-emergence herbicide options available for landscape beds and explain why Dr. Marble considers graminicides underutilized.
**Key Points to Identify:**
- Graminicides (sethoxydim, clethodim, fluazifop, fenoxaprop — sold as Segment, Envoy, Fusilade, Acclaim) can be applied over the top of hundreds of broadleaf ornamentals because they only affect true grasses
- Other selective options (Basagran for sedge, Lontrel/clopyralid for Asteraceae and legumes, Certainty for sedge in ground covers) are limited to 20–30 labeled ornamentals each
- Many practitioners default to risky glyphosate spot treatments around ornamentals rather than using these safer selective alternatives

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### Review Task 9
**Watch:** 45:52 – 50:22
**Task:** From the Q&A discussion, explain the three signal word levels, how they affect PPE requirements, and describe two practical steps to reduce spray drift.
**Key Points to Identify:**
- Signal words in order of increasing toxicity: Caution (lowest), Warning, Danger/Poison (highest) — based on routes of exposure (skin, eye, etc.)
- Higher signal words require more PPE and may trigger restricted use product requirements with stricter record-keeping
- To reduce physical drift: use coarser nozzle tips (larger droplets fall more readily) and lower sprayer pressure (avoids fine mist)

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*Processed for UGA Center for Urban Agriculture / GTBOP Archives*
*Source: Corrected SRT (Stage 1) — GTBOP_Transcript_2023-07-13_WeedControlOrnamentals.srt (618 blocks)*