# GTBOP Moodle Review Activities
## Weed Control in Turf — A Review of the Basics and Recent Updates

**Webinar Date:** November 17, 2017
**Speaker:** Dr. Patrick McCullough, Weed Scientist, University of Georgia
**Series:** Green & Commercial
**Course Context:** Weed Science Certificate Course
**Source:** Corrected SRT (Stage 1) + Archive Package (Stage 2)

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### Review Task 1: Weed Identification Characteristics
**Watch:** 2:43 – 9:33
**Task:** As McCullough walks through the diagnostic characteristics used to identify weed species, list the six types of characteristics he covers and note one specific example species he uses to illustrate each.
**Key Points to Identify:**
- Seed heads (e.g., bahiagrass vs. dallisgrass, Poa annua panicle)
- Ligules (e.g., barnyardgrass absent ligule vs. crabgrass fleshy ligule)
- Flowers (e.g., two-petal vs. three-petal day flower species)
- Leaf arrangement on stems (alternate vs. opposite)
- Pubescence/hairs (e.g., smooth crabgrass vs. large crabgrass vs. southern crabgrass)
- Leaf markings (e.g., white clover chevron vs. spotted burr clover purple dot)

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### Review Task 2: Cultural Practices and Weed Competition
**Watch:** 17:08 – 21:26
**Task:** McCullough presents two research studies demonstrating how cultural practices influence weed populations. Summarize the key finding of each study, including the specific numbers he provides.
**Key Points to Identify:**
- Mowing height study: tall fescue at 1 inch vs. 4 inches — crabgrass reduced from 95% to 0%
- Irrigation study: daily watering vs. as-needed — dollarweed cover increased 5–6 fold with daily irrigation
- The connection between these findings and reducing the need for herbicide inputs

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### Review Task 3: Pre-Emergent Herbicide Mechanism
**Watch:** 24:07 – 27:00
**Task:** McCullough explains a common misconception about how pre-emergent herbicides work. Identify what pre-emergent herbicides do NOT do and then describe the actual mechanism in three steps (where the product goes, how the weed encounters it, what happens to the seedling).
**Key Points to Identify:**
- Pre-emergents do NOT prevent germination
- Product binds in the upper half-inch of the soil profile
- Germinating seedling roots and shoots absorb the herbicide from soil water solution
- Herbicide inhibits cell division; seedling fails to establish healthy roots and dies

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### Review Task 4: Herbicide Resistance Selection Pressure
**Watch:** 37:31 – 43:33
**Task:** McCullough uses a year-by-year diagram to explain how herbicide resistance develops through selection pressure. Trace the progression from Year 1 through Year 5 and explain why simply increasing the herbicide rate does not solve the problem.
**Key Points to Identify:**
- Year 1: one naturally resistant biotype survives among susceptible population
- Repeated applications kill susceptible plants, allowing resistant biotype to reproduce
- By Year 5: resistant biotype dominates the population
- Target-site resistance: altered binding site means the herbicide simply does not work regardless of rate (300x rate example with Monument)

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### Review Task 5: Resistance Management Through Mode of Action Combinations
**Watch:** 46:05 – 50:48
**Task:** McCullough describes the results of resistance management trials at three golf courses. For each course, note which herbicides worked, which failed, and explain why the combination of a sulfonylurea with simazine succeeded at all three locations.
**Key Points to Identify:**
- Different resistance profiles at each golf course (Barricade-resistant at courses 1 and 2; simazine-resistant at courses 1 and 3; sulfonylurea-resistant at course 2)
- Specticle controlled dinitroaniline-resistant Poa at all sites
- Sulfonylurea + simazine combination provided complete control at all three courses
- Cost-effectiveness: simazine adds a second mode of action for ~$5/acre

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### Review Task 6: New Product Comparison — Halauxifen Formulations
**Watch:** 55:01 – 1:01:21
**Task:** McCullough introduces three new products from Dow that all contain halauxifen. Create a comparison noting the other active ingredients in each product, which turfgrass species each is labeled for, and which product would be appropriate for a centipedegrass lawn.
**Key Points to Identify:**
- RELZAR: halauxifen + florasulam — all major warm and cool-season species; one labeled rate
- Game On: halauxifen + 2,4-D choline + fluroxypyr — primarily cool-season grasses plus bermudagrass and zoysiagrass; NOT centipedegrass or St. Augustinegrass (2,4-D sensitivity)
- Switchblade: halauxifen + dicamba + fluroxypyr — warm and cool-season including centipedegrass and St. Augustinegrass
- For a centipedegrass lawn: RELZAR or Switchblade, not Game On

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## Review Activity Summary

**Total Tasks:** 6
**Coverage Distribution:**
- Weed Identification (early): Task 1
- Cultural Practices (early-mid): Task 2
- Pre-Emergent Science (mid): Task 3
- Herbicide Resistance (mid-late): Tasks 4, 5
- New Products (late): Task 6

**Design Notes:** Tasks are structured to guide self-paced viewing by directing learners to specific segments. Each task asks for synthesis beyond simple recall — listing, comparing, tracing progressions, or correcting misconceptions — to promote active engagement with the video content.

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*Generated for UGA Center for Urban Agriculture / GTBOP Moodle Certificate Course — Weed Science*
*Source: Corrected SRT (Stage 1) — GTBOP_Transcript_2017-11-17_WeedControlTurf.srt (649 blocks)*