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GTBOP Moodle Review Activities

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Weed Control in the Landscape & Nursery — Dr. Mark Czarnota (November 18, 2021)

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Source: Corrected SRT (Stage 1) — GTBOP_Transcript_2021-11-18_WeedControl.srt (786 blocks) +Structural Reference: Stage 2 Archive Package — GTBOP_Archive_Summary_2021-11-18_WeedControl.md +Review Tasks: 6

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Review Task 1

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Watch: 4:23 – 6:40 +Task: List the six characteristics Dr. Czarnota identifies as predictors of weediness, then describe the specific real-world example he uses for the first characteristic. +Key Points to Identify: +- The six characteristics (vegetative reproduction, abundant seed production, rapid establishment, seed dormancy, adaptive traits, disturbed site colonization) +- Yellow and purple nutsedge as the example of vegetative reproductive structures +- Pigweed seed production numbers (5,000–10,000 seeds per plant)

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Review Task 2

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Watch: 15:44 – 18:06 +Task: Identify the four biological control methods Dr. Czarnota describes and note the specific target weed or pest for each. For one method, describe why it was discontinued. +Key Points to Identify: +- Grass carp for submerged aquatic weeds (8–10 per surface acre) +- Goats for kudzu (followed by herbicide on regrowth) +- Thistle weevil for musk thistle (larvae prevent seed development over 2–3 years) +- DeVine bioherbicide for strangler vine in citrus (worked too well — eliminated the vine and left no host for the biocontrol agent)

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Review Task 3

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Watch: 21:07 – 23:43 +Task: Explain the key difference between how pre-emergent and post-emergent herbicides work, and identify the critical weather requirement for each type after application. +Key Points to Identify: +- Pre-emergent: applied before germination, needs 0.5–1 inch of rain to move into top quarter inch of soil +- Post-emergent: applied after emergence, needs a dry period for leaf absorption +- Glyphosate as the only broad-spectrum systemic (phloem-loaded) post-emergent herbicide

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Review Task 4

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Watch: 26:20 – 29:08 +Task: Describe the modes of action for glyphosate and the dinitroaniline herbicides. For glyphosate, identify the three amino acids affected and explain why this matters for mammalian safety. +Key Points to Identify: +- Glyphosate inhibits EPSP synthase, blocking production of tryptophan, phenylalanine, and tyrosine +- The EPSP synthase pathway does not exist in animals — humans obtain these amino acids through diet +- Dinitroanilines disrupt microtubule formation during cell division, preventing chromosome separation +- Visual symptom of dinitroaniline overdose: club rooting

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Review Task 5

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Watch: 29:42 – 35:16 +Task: From the pre-emergent and post-emergent products Dr. Czarnota reviews, identify the two products he recommends most highly for landscape use and note their key advantages and any limitations. +Key Points to Identify: +- Dimension (dithiopyr): most underutilized; safe on turfgrasses, broad woody ornamentals, some perennials and annuals +- Marengo (indaziflam): up to 16 weeks control; established woody ornamentals only; does not control nutsedge +- Combination granular products (Snapshot, FreeHand) provide both pre-emergent control and oxyfluorfen burndown

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Review Task 6

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Watch: 36:40 – 39:30 +Task: List the common application errors Dr. Czarnota identifies that reduce herbicide effectiveness, and note his recommended application frequency for field versus container production. +Key Points to Identify: +- No rain after pre-emergent application (needs rain within 72 hours) +- Rain immediately after post-emergent application +- Poorly calibrated equipment +- Wrong herbicide for the target weed +- Applying pre-emergent after weeds have already germinated +- Field: 2–4 applications/year; Containers: 4–6 applications/year

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Generated for UGA Center for Urban Agriculture / GTBOP Moodle Course Activities +Source: Corrected SRT (Stage 1) — GTBOP_Transcript_2021-11-18_WeedControl.srt (786 blocks) +Structural Reference: Stage 2 Archive Package

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