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# GTBOP YouTube Description

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

Weed Control in the Landscape & Nursery with Dr. Mark Czarnota

Dr. Mark Czarnota, weed scientist at the University of Georgia Griffin Campus, presents a comprehensive overview of weed control strategies for landscape and nursery professionals. Topics include weed identification and life cycles, physical and biological control methods, pre-emergent and post-emergent herbicide categories, recommended products including Dimension (dithiopyr) and Marengo (indaziflam), herbicide modes of action, glyphosate safety research, and practical application tips. The session concludes with audience Q&A on torpedograss, Virginia buttonweed, and bermudagrass control in ornamentals.

Speaker: Dr. Mark Czarnota, Associate Professor of Horticulture (Weed Science), UGA Griffin Campus Moderator: Dr. Shimat Joseph, Turfgrass Entomologist, UGA Griffin Campus Series: GTBOP Green & Commercial CEU Categories: 10, 21, 22, 23, 24, 27, 31, 32, 35

🕐 TIMESTAMPS 0:00 Introduction and Speaker Background 3:02 What Is a Weed? Definitions and Weediness Predictors 5:13 Challenging Weed Problems in Nursery Production 9:03 Weed Identification and Plant Life Cycles 11:55 Weed Control Methods: Physical Removal and Barriers 15:44 Biological Control: Grass Carp, Goats, Thistle Weevil 19:50 Chemical Weed Control: Impact of Major Herbicides 21:07 Pre-Emergent vs. Post-Emergent Herbicides 25:16 Trade Names, Active Ingredients, and Cost Savings 26:20 Herbicide Modes of Action 29:42 Pre-Emergent Herbicides for Landscape and Nursery 31:17 Post-Emergent and Combination Herbicides 35:16 Recommended Products: Marengo, BroadStar, SureGuard 36:40 Best Practices and Common Application Errors 40:21 Herbicide Fate, Organic Options, and Glyphosate Safety 43:40 Glyphosate Damage, Adjuvants, and Future Technologies 44:54 Q&A: Torpedograss, Virginia Buttonweed, Bermudagrass Control

❓ Q&A HIGHLIGHTS

Q: Which pre-emergent herbicides are recommended most for landscape use? A: Dimension (dithiopyr) is one of the most underutilized pre-emergent herbicides — safe for most turfgrasses, broad woody ornamentals, and some perennials and annuals. Marengo (indaziflam) provides up to 16 weeks of control in established woody ornamentals but does not control nutsedge. BroadStar (flumioxazin) as a granular and SureGuard as its sprayable form are also recommended.

Q: What is the difference between pre-emergent and post-emergent herbicides? A: Pre-emergent herbicides are applied to bare soil or mulch before weed seeds germinate and need a half-inch to one inch of rain to activate, providing 8–12 weeks of control. Post-emergent herbicides are applied after weeds have emerged and need a dry period after application to be absorbed into the plant.

Q: How can bermudagrass creeping into ornamental beds be selectively controlled? A: Clethodim (Envoy) gives approximately 10–15% better activity than alternatives, providing three to four months of suppression. Other options include Segment and Fusilade DX. Glyphosate also controls bermudagrass but cannot be used selectively over ornamentals.

Q: What product works best for controlling torpedograss? A: Drive (quinclorac) controls torpedograss very well. It is not yet labeled for over-top use on ornamentals but research at UGA has found it fairly safe on most woody ornamentals.

Q: What common mistakes reduce the effectiveness of herbicide applications? A: Failing to irrigate after pre-emergent applications (they need rain within 72 hours), rain too soon after post-emergent applications, poorly calibrated equipment, poor herbicide selection, and applying pre-emergent herbicides after weeds have already germinated.

📌 RESOURCES Labels & Safety Data Sheets: CDMS.net Turfgrass Weed Control: Contact Dr. Patrick McCullough, UGA

Presented by the University of Georgia Center for Urban Agriculture Getting the Best of Pests (GTBOP) Webinar Series