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# 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)

### 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

### 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

### 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)

### 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

### 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

### 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%

### 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

### 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

### 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)

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