Speakers: Dr. Alfredo Martinez, Professor of Plant Pathology, UGA Griffin Campus; Dr. Clint Waltz, Professor and Extension Specialist, UGA Griffin Campus
Webinar Date: November 14, 2024
Moderator: Dr. Shimat Joseph, UGA Extension Entomologist
Duration: 56:38
NARRATIVE SUMMARY
This comprehensive industry update featured two leading UGA turfgrass specialists providing critical fall and winter management guidance for Georgia’s Green Industry professionals. Dr. Alfredo Martinez opened with an in-depth disease management presentation emphasizing the critical importance of fall as an active disease season for warm-season grasses. He detailed management strategies for Rhizoctonia large patch, currently very active in zoysiagrass and Seashore Paspalum, stressing early detection and the importance of reaching the crown level with fungicide applications using at least three gallons per thousand square feet. Dr. Martinez explained spring dead spot management, noting that fall is the optimal treatment window since infections occur in fall, plant death happens in winter, and symptoms appear in spring. He emphasized that this root disease requires aggressive applications with products watered in to reach the soil level.
Dr. Martinez introduced seven new fungicide products available in 2024, including Serrara for Pythium management, Kalida for broad-spectrum disease control, Densicor and Resilia for root diseases, and several others targeting dollar spot, Rhizoctonia, and multiple turfgrass pathogens. He highlighted landscape-specific formulations including Heritage SC, Compendium, and other products now available for residential applications. Additional disease coverage included microdochium patch as a cold-season concern and Bipolaris leaf spot, which shows direct correlation with low potassium levels and requires attention to nutrient management alongside fungicide applications.
Dr. Clint Waltz provided essential seasonal guidance on fertilization timing, emphasizing that nitrogen applications on warm-season grasses should cease as root activity slows below 65°F. He cautioned against winterizer fertilizers marketed for fall application, clarifying these are inappropriate for dormant warm-season turf. For tall fescue, he outlined the proper fall fertilization schedule with one-pound nitrogen applications in September/October and November. His soil chemistry discussion covered pH management fundamentals, explaining how hydrogen ion concentration affects nutrient availability, particularly phosphorus uptake. Dr. Waltz detailed lime application strategies, recommending fall as ideal timing for warm-season grasses to allow three to four months for activation before spring growth. He introduced UGA’s calcium chloride buffer capacity testing method, which replaced older methods while maintaining accuracy and reducing hazardous waste.
Weed management coverage focused extensively on Poa annua control, with Dr. Waltz presenting University of Tennessee research showing germination patterns and optimal herbicide timing. He recommended pre-emergence herbicides through early October, followed by pre- and post-emergence combinations for the remainder of fall and winter. Product options included dinitroaniline herbicides, sulfonylureas for bermudagrass and zoysiagrass, and triazines with both pre- and post-emergence activity. The presentation concluded with audience questions addressing winter kill prevention research, buffer capacity definitions, and bermudagrass mowing height impacts on turf quality and disease susceptibility.
YOUTUBE TIMESTAMPS
0:00 Introduction and Webinar Overview
0:27 Dr. Alfredo Martinez Introduction and Background
1:22 Disease Management Update: Fall Activity Period
2:22 Weather Patterns and Disease Susceptibility
3:05 Key Diseases: Dollar Spot and Bipolaris Leaf Spot
3:20 Rhizoctonia Large Patch Overview
4:27 Large Patch: Current Activity in Zoysiagrass
4:47 Pathogen Biology and Symptomology
6:01 Susceptible Grass Species and Timing
6:34 Rhizoctonia solani: Diagnostic Features
7:19 Management: Early Detection Importance
7:52 Cultural Practices: Thatch Reduction
9:04 Chemical Control Options for Large Patch
10:06 Application Timing: Prevention vs. Curative
10:28 Gallonage Requirements for Crown Diseases
11:08 Strobilurin Fungicides for Large Patch
11:42 DMI Fungicides: Propiconazole and Others
12:03 SDHI Fungicides: Fluxapyroxad and Penthiopyrad
13:24 Spring Dead Spot: Disease Overview
14:04 Spring Dead Spot: Bermudagrass Specificity
14:44 Symptom Recognition: Dead vs. Dying Grass
15:02 Infection Timing: Fall, Winter, Spring Pattern
15:27 Disease Severity and Site Impacts
15:47 Root System Damage and Temperature Effects
16:01 pH Influence: 6.3 and Above
16:52 Cultural Management: Nitrogen and pH
17:21 Potassium and Root Growth Promotion
18:07 Fungicide Options for Spring Dead Spot
18:40 Strobilurins and DMI Combinations
19:06 Fall Timing Critical for Control
19:36 Gallonage and Watering In Requirements
20:15 New Products: Serrara for Pythium Control
21:03 Kalida: Combination SDHI and DMI Product
21:40 Densicor and Resilia: Root Disease Specialists
22:05 Ascernity: Fairy Ring Label Expansion
22:32 Posterity Product Line Extensions
23:00 Landscape Products: Heritage SC and Compendium
23:40 Additional Professional Products Overview
24:23 Microdochium Patch: Cold Season Disease
25:07 Preventative Applications for Microdochium
26:01 Cream Leaf Blight: Minor Concern
27:01 Control Options for Microdochium
28:13 Bipolaris Leaf Spot: Current Activity
28:40 Spore Dispersal and Spread Patterns
29:07 Potassium Deficiency Connection
29:16 Fungicide Products for Bipolaris
29:40 Mowing and Sanitation Practices
30:03 Transition to Dr. Clint Waltz
30:17 Dr. Clint Waltz Introduction
30:44 Fall and Winter Seasonal Practices Overview
31:05 Nitrogen Fertilization: Marketing vs. Science
31:28 Root Temperature: 65°F Critical Threshold
32:04 Current Root Activity in Georgia
32:16 Early Spring Fertilizers: Wrong for Fall
32:34 Winterizer Products: Not for Warm-Season Grass
33:05 Tall Fescue: Appropriate Fall Fertilization
33:47 October Drought Impacts on Fertilizer
34:00 Tall Fescue Schedule: Two Fall Applications
35:05 Presentation Sharing Issue Resolution
35:49 Fertilization Review and Product Analysis
36:01 Soil Chemistry Fundamentals
36:16 pH Definition: Hydrogen Ion Concentration
36:36 Sources of Hydrogen Ions in Soil
37:05 Plant Contributions to Soil pH
37:40 Ammonium Uptake and pH Effects
38:03 Calcium Uptake and Neutrality
38:25 Phosphorus Availability and pH Range
39:20 Nutrient Use Efficiency: The Sweet Spot
39:44 Soil Testing: The Only Way to Know pH
40:10 Lime Buffer Capacity Testing
40:46 UGA Calcium Chloride Method
41:19 Raising pH with Lime Products
41:52 Splitting Lime Applications
42:27 Timing: Fall Application Benefits
43:00 Lime Activation Period: 3-4 Months
43:29 Tall Fescue Lime Timing: Midsummer
43:45 Lowering pH: Acidifying Fertilizers
44:20 Split Pea Sulfur Applications
44:40 Elemental Sulfur for Extreme pH
45:16 Poa annua: The Cockroach of Weeds
45:40 Germination Timing and Soil Temperature
46:03 Prolific Nature of Annual Bluegrass
46:33 University of Tennessee Emergence Research
47:00 Pre-Emergence Herbicide Timing
47:25 Pre- and Post-Emergence Combinations
47:37 Dinitroaniline Pre-Emergence Options
48:01 Sulfonylurea Post-Emergence Products
48:20 MSM and Manor: Early Seedling Control
48:44 Triazine Products: Atrazine and Simazine
49:03 Pre-Emergence Activity Duration
49:24 Tall Fescue Poa Control Challenges
49:47 Pre-Emergence Options for Tall Fescue
50:07 Post-Emergence Products: Limited and Expensive
50:23 Closing Remarks and Resources
50:40 Pest Control Recommendations Availability
51:05 Website: georgiaturf.com Resources
51:17 Q&A Session Begins
51:27 Winter Kill Prevention Research Discussion
52:08 Virginia Tech Late-Season Nitrogen Work
52:44 Proper Mowing Height Recommendations
53:05 Desiccation vs. Winter Kill in Georgia
53:40 Disease Considerations with Nitrogen
54:29 Transition Zone Context
54:49 Buffer Capacity Definition and Explanation
55:06 Soil Parent Material and pH Resistance
55:40 Soil Testing: The Only Reliable Method
55:49 Bermudagrass Mowing Height Question
56:05 Three-Inch Height Problems: Shading and Density
56:26 Disease Promotion and Canopy Issues
56:38 Closing Thank You
QUESTIONS & ANSWERS
Q: What are the critical timing considerations for large patch management in fall?
A: Right now we are probably at the tail end of prevention and entering curative action. The importance is timing of application and gallonage. For crown diseases like large patch, use at least three gallons per thousand square feet or water in very lightly to reach the crown area. Early detection is key for disease prevention, and training crews to recognize symptoms is important.
Q: Which new fungicide products are available for 2024 and what are their target diseases?
A: Seven new products were highlighted: Serrara targets Pythium and root diseases; Kalida combines fluxapyroxad and fluopyram for dollar spot, Bipolaris, take-all root rot, and Rhizoctonia; Densicor is a DMI for foliar and root diseases; Resilia combines prothioconazole and propamocarb for root diseases; Ascernity now includes fairy ring on the label; Posterity XT and Forte are enhanced versions with more active ingredient; and Encartis combines boscalid with chlorothalonil.
Q: Why is fall the critical time for spring dead spot management rather than spring?
A: Spring dead spot infections happen in the fall, plant death occurs in winter, and symptoms appear in spring. If you try to treat in spring, you’re going against the current. The timing for spring dead spot management is right now in fall. Since it’s a root disease, you need more than three gallons per thousand square feet or water the product in to go down to the soil and crown level.
Q: How does Bipolaris leaf spot differ from other turfgrass diseases in its management approach?
A: Bipolaris leaf spot has an almost direct relationship with low potassium levels. The first management step is to check potassium levels in the soil. The disease is dispersed by spores through rain, mowing equipment, and foot traffic, so sanitation is critical. Mow heavily affected areas last, catch clippings, and use products like iprodione, mancozeb, strobilurins, or SDHIs in combination with adequate potassium levels.
Q: What are the landscape-specific fungicide products now available for residential applications?
A: Several products are now formulated specifically for landscape companies: Heritage SC (azoxystrobin in a unique formulation), Compendium (formerly Armada, azoxystrobin plus propiconazole), and azoxystrobin standalone products. Additionally, Fosclaw, Castlon, Indow, and Compendium are available for residential and landscape-friendly applications, making disease management more accessible beyond golf course settings.
Q: At what soil temperature should nitrogen fertilization cease for warm-season grasses?
A: Nitrogen fertilization should stop when four-inch root zone temperatures drop below 65°F. At this temperature, root growth and root activity decline significantly. While Griffin’s temperatures are still in the mid-60s in mid-November, the grass is responding to environmental cues and slowing down. Winterizer fertilizers marketed for fall application are absolutely not appropriate for warm-season grasses at this time.
Q: What is lime buffer capacity and why does it matter for pH management?
A: Buffer capacity is the soil’s resistance to change in pH based on the parent material. A straight sand has very little buffer capacity because there’s no organic matter or clay to buffer it. Different soils have different buffering capacities. The only way to know your buffering capacity is through a soil test, which tells you not just whether you need lime, but how much lime you need to achieve the appropriate pH range.
Q: When is the ideal time to apply lime to warm-season turfgrass?
A: Mid to late fall or early winter is ideal for warm-season grasses. Now is a really good time because warm-season grasses are going dormant, we’re four to five months from spring green-up, and lime takes three to four months to activate and change soil chemistry. This allows wintertime rains to work it in and have it ready for efficient nutrient use when spring growth begins.
Q: What is the proper pre- and post-emergence herbicide strategy for Poa annua control?
A: From early August through early October, use pre-emergence herbicides only. After the first of October when the biggest germination jump occurs, use a mixture of pre-emergence and post-emergence herbicides. Pre-emergence options include dinitroaniline products, pendimethalin, prodiamine, dithiopyr, and Specticle. For bermudagrass and zoysiagrass, add sulfonylureas like Katana, Revolver, or Monument. For early seedlings, MSM or Manor work well, and triazines provide both pre- and post-emergence activity.
Q: What does recent research say about preventing winter kill in warm-season grasses?
A: A multi-university study including Maryland, Clemson, Arkansas, and Louisiana identified three factors: light late-season nitrogen applications for golf courses and sports fields (not necessary for landscapes), proper mowing height around three-quarters to one inch, and keeping grass hydrated. However, for Georgia, it’s more accurately called “winter impatience” rather than winter kill—killing established bermudagrass is very difficult, and people often just get impatient waiting for spring green-up.
Q: Why is mowing bermudagrass at three inches problematic?
A: Bermudagrass at three inches tends to shade itself out. Bermudagrass really likes light, so mowing at a high height reduces canopy density. The canopy also harbors humidity, promoting diseases, and the grass becomes very leggy, further diminishing density. For homeowner lawns, the ideal mowing height is around one and a half inches to maintain good turf quality.
Q: What are the fertilization recommendations for tall fescue in fall and spring?
A: Tall fescue should receive two one-pound nitrogen applications in fall: one in late September or October, and a second in November. This totals two pounds over the fall. In spring, apply two additional one-pound applications—one in mid-February around Valentine’s Day, and another around April 1st. Good fertilizer analysis examples include 16-4-8 or 32-8 for tall fescue applications.
ADDITIONAL RESOURCES
UGA Turfgrass Resources:
- Website: georgiaturf.com (2024 Turfgrass Pest Control Recommendations for Professionals)
- Publication sections available: Disease, Insect, and Weed management
- Seasonal calendars included
Soil Testing:
- UGA Extension County Offices
- UGA Soil Testing Laboratory (calcium chloride buffer method)
Weather and Climate Data:
- Georgia Automated Environmental Monitoring Network
- Four-inch soil temperature monitoring for fertilization timing
Upcoming Programs:
- Check georgiaturf.com for field days and educational events
- County extension offices for local programming
For technical questions on turfgrass disease management, contact Dr. Alfredo Martinez at the UGA Griffin Campus. For questions on turfgrass fertility, soil management, and weed control, contact Dr. Clint Waltz at the UGA Griffin Campus.