Speakers: Dr. Jean Williams-Woodward, Extension Plant Pathologist, University of Georgia Athens; Dr. Shimat Joseph, Turfgrass and Ornamental Entomologist, University of Georgia
Webinar Date: November 14, 2024
Moderator: Rich Braman, UGA Center for Urban Agriculture
Duration: 50:12
NARRATIVE SUMMARY
This ornamentals industry update featured two University of Georgia specialists providing critical information on emerging plant diseases and invasive insect pests affecting Georgia’s landscape and nursery industries.
Dr. Jean Williams-Woodward, Extension Plant Pathologist based in Athens, opened with an update on vascular streak dieback (VSD), a condition affecting deciduous trees, particularly redbuds. The organism associated with VSD has been found on approximately 30 plant species, with research from Tennessee State University ongoing. Dr. Williams-Woodward noted that lighter-colored redbud varieties appear more susceptible than purple-leaved cultivars. She explained that bot canker, caused by Botryosphaeria fungi, remains prevalent in red maples, with the fungus living endophytically within plants and becoming problematic during water stress. Systemic fungicides including propiconazole and mefentrifluconazole (Cevya), applied with Pentra-Bark adjuvant, have shown effectiveness in reducing bot canker symptoms.
The presentation covered anthracnose diseases, which were particularly severe during the wet spring of 2024, affecting Japanese maples, oaks, sycamores, and London plane trees. Dr. Williams-Woodward emphasized that pruning dead branch tips where the fungus overwinters is essential for reducing future infections. Her boxwood blight research demonstrated that with intensive management—including biweekly fungicide applications and restricting pet access—landscapes can maintain boxwoods despite infection. However, she cautioned that most homeowners cannot sustain this level of care. She also introduced hydrangea ringspot virus, a mechanically-transmitted virus causing leaf distortion and reduced flowering that is spreading through propagation and pruning activities.
Dr. Shimat Joseph provided updates on three invasive insect threats. The box tree moth, established in northeastern states, has been detected in Tennessee and South Carolina but not yet Georgia. This caterpillar pest can decimate boxwoods by feeding on both leaves and stems. Dr. Joseph announced that spotted lanternfly was first detected in Georgia in Fulton County in October 2024, emphasizing the importance of early detection. He concluded with information on an invasive thrips species present in Georgia that resembles chili thrips damage and is commonly misdiagnosed as broad mite injury. Management options including spinosad, spinetoram, and systemic insecticides were discussed for all three pests.
YOUTUBE TIMESTAMPS
0:00 Introduction and Welcome
0:16 Dr. Jean Williams-Woodward Introduction
1:01 Setting Up Presentation
1:27 Overview: Plant Diseases Update
1:42 Vascular Streak Dieback (VSD) in Deciduous Trees
2:06 VSD in Redbuds: Symptoms and Research
2:30 VSD vs. Bot Canker Comparison
2:46 Bot Canker: Botryosphaeria Complex
3:04 Bot Canker: Wound Entry and Cambial Damage
3:32 Bot Canker: Endophytic Nature of the Fungus
4:00 Water Stress and Bot Canker Development
4:27 Fungicide Treatments: Propiconazole and Mefentrifluconazole
4:51 Pentra-Bark Adjuvant for Bark Penetration
5:19 VSD Organism Discussion
5:33 VSD Symptoms: Leaf Scorching and Variety Susceptibility
5:59 VSD Research: Widespread Distribution
6:25 VSD as Possible Endophyte
7:04 Postiva Fungicide for VSD Management
7:32 VSD: Sanitation and Timing of Applications
8:00 VSD Identification on Red Maples
8:44 VSD vs. Verticillium Wilt: Diagnostic Differences
9:31 Anthracnose Diseases: Wet Spring Impact
9:42 Anthracnose on Japanese Maples
9:56 Aureobasidium and Discula: Causative Fungi
10:09 Anthracnose Stem Cankers
10:51 Pruning to Remove Overwintering Inoculum
11:18 Fungicides for Anthracnose: Georgia Pest Management Handbook
11:44 Anthracnose on Oaks, Sycamores, and London Plane Trees
12:15 Oak Anthracnose vs. Leaf Miners
12:50 Severe Anthracnose: Leaf Drop and Recovery
13:28 Boxwood Blight: History and Impact
13:59 Barnsley Gardens Case Study
14:27 Managing Boxwood Blight in Existing Landscapes
15:17 Boxwood Blight Symptoms: Leaf Litter and Black Stem Lesions
15:46 Kingston Boxwood: Management Success Story
16:36 Fungicide Spray Programs for Boxwood Blight
16:58 Pet Transmission of Boxwood Blight
17:17 American Boxwood vs. Korean Types
18:18 Boxwood Blight Pathogen Survival in Soil
19:05 Boxwood Blight: Reinfection Risk
19:32 Boxwood Blight Management Tactics Summary
20:06 Disinfesting Tools and Clothing
20:33 Resistant Boxwood Varieties
21:02 The Cat Named “Vector”
21:34 Rose Rosette Virus Reminder
22:01 Hydrangea Ringspot Virus: New Identification
22:31 Hydrangea Ringspot: Mechanical Transmission
23:05 Hydrangea Ringspot: Symptoms on Cuttings
23:43 Propagation Concerns for Hydrangea Virus
24:03 Transition to Entomology Presentation
24:22 Dr. Shimat Joseph Introduction
25:03 Turf and Ornamental Pest Management Website
25:40 Box Tree Moth: Introduction to Topic
26:07 Box Tree Moth: Current US Distribution
26:56 Box Tree Moth: Damage Potential
27:34 Box Tree Moth: Adult Identification
28:03 Box Tree Moth: Egg Description
28:41 Box Tree Moth: Larval Identification and Behavior
29:30 Box Tree Moth: Overwintering Biology
30:00 Box Tree Moth: Life Cycle Completion
30:47 Box Tree Moth: Generation Potential in South
31:25 Box Tree Moth: Damage Progression
31:59 Box Tree Moth: Caterpillar Pictures and Webbing
32:25 Box Tree Moth: Management Options
33:03 Box Tree Moth: BT kurstaki and Pyrethroids
33:26 Spotted Lanternfly: Introduction
33:57 Spotted Lanternfly: Host Range
34:28 Spotted Lanternfly: Current Spread Map
35:03 Spotted Lanternfly: Tennessee Detections
35:56 Spotted Lanternfly: Egg-Laying Behavior
36:46 Spotted Lanternfly: Egg Mass Camouflage
37:16 Spotted Lanternfly: First Georgia Detection (Fulton County)
38:15 Spotted Lanternfly: Urban Host Trees
38:39 Spotted Lanternfly: Phloem Feeding and Honeydew
39:17 Spotted Lanternfly: Adult Description
39:36 Spotted Lanternfly: Egg Mass Details
40:08 Spotted Lanternfly: Nymphal Stages
40:42 Spotted Lanternfly: Sap Oozing and Sooty Mold
41:05 Spotted Lanternfly: Honeydew Fermentation
41:32 Lampshade Trap for Spotted Lanternfly
41:59 Spotted Lanternfly: Rail Car Spread
42:36 Spotted Lanternfly: Management Options
43:20 Systemic Insecticides: Imidacloprid and Dinotefuran
43:57 Transition to Questions
44:16 Invasive Thrips Species: Introduction
44:31 Thrips Distribution and First Detection
45:10 Thrips Survey in Garden Centers
45:24 Thrips: Why This Pest is Dangerous
45:52 Thrips: Small Size and Detection Challenges
46:07 Thrips: Misdiagnosis as Mite Damage
46:29 Thrips: Life Cycle and Biology
47:07 Thrips: Host Plants Including Pepper
47:34 Thrips: Gardenia Damage
47:51 Chili Thrips Comparison
48:00 Broad Mite vs. Thrips Damage Appearance
48:11 Thrips Management: Early Detection Key
48:17 Management Products: Xxpire, Spinosad, Mainspring
48:50 Closing and Q&A Opportunity
49:00 Sign-In Sheet Reminder
49:40 Final Thanks and Closing
50:00 Speaker Availability for Questions
QUESTIONS & ANSWERS
Q: What is the difference between vascular streak dieback and bot canker in landscape trees?
A: Both conditions can cause dieback in deciduous trees, but they have distinct characteristics. Bot canker, caused by Botryosphaeria fungi, creates visible cankers with dark brown discoloration in cambial tissue, typically entering through wounds. The fungus lives endophytically in the plant and becomes problematic during water stress. Vascular streak dieback shows streaking in the vascular tissue when stems are cut vertically, similar in appearance to Verticillium wilt. VSD appears worse on lighter-colored redbud varieties and is associated with a fungal organism that researchers have found on approximately 30 different plant species.
Q: How can systemic fungicides be applied effectively for bot canker management in trees?
A: Systemic fungicides including propiconazole and mefentrifluconazole (sold as Cevya) can be applied with Pentra-Bark, an adjuvant that helps move the fungicide through the bark and into vascular tissue. Applications in fall and winter seem to provide good control of bot canker by reducing the dieback symptoms. This bark spray approach allows the product to reach the colonized internal tissues where the fungus is active.
Q: What management approach is recommended for anthracnose diseases in landscape trees?
A: The most important management step is pruning to remove dead branch tips where the anthracnose fungus overwinters. Without removing this inoculum source, spores will splash onto new foliage the following spring, causing reinfection. Fungicides can be applied preventatively in spring to protect new foliage, with options listed in the Georgia Pest Management Handbook. For severe infections causing heavy leaf drop, rake and remove fallen leaves; the tree will produce new growth from axillary buds that typically escapes infection as environmental conditions change.
Q: Can boxwood blight be managed in existing landscape plantings, or must infected plants be removed?
A: Boxwood blight can potentially be managed in place, but it requires intensive, ongoing effort that many homeowners cannot sustain. Successful management requires fungicide applications every two weeks throughout the growing season, restricting pet access to prevent spread on fur, and diligent sanitation. Research at sites like Barnsley Gardens shows that boxwoods can survive with the disease present when these practices are followed. However, for most landscapes, removal of infected plants remains the most practical recommendation. Korean-type boxwoods retain leaves better than American and dwarf English varieties when infected.
Q: How does hydrangea ringspot virus spread, and what symptoms should professionals look for?
A: Hydrangea ringspot virus is mechanically transmitted, meaning it spreads through pruning activities and propagation from infected stock plants. Symptoms include tiny ring patterns developing on leaves around the veins, leaf distortion, and reduced or distorted flowering. The symptoms can initially appear similar to thrips damage or herbicide injury. There is no cure for this virus, so prevention through using clean stock and sanitizing pruning tools between plants is essential. Landscape companies should avoid propagating from symptomatic plants.
Q: What makes the box tree moth a significant threat to boxwoods if it reaches Georgia?
A: The box tree moth can cause complete defoliation and plant death because caterpillars feed on both leaves and stem tissue. When populations build over multiple generations, they can decimate boxwood plants by disrupting water and nutrient movement through stem feeding. The pest is currently established in northeastern states and has been detected in Tennessee and South Carolina. It can complete up to five generations annually in cooler climates and potentially more in the South. Early detection and treatment of young caterpillars with products like spinosad, pyrethroids, or Bt kurstaki is critical for effective management.
Q: What is the current status of spotted lanternfly in Georgia, and how does it spread?
A: As of October 2024, spotted lanternfly was first detected in Georgia in Fulton County, according to the Georgia Department of Agriculture. The pest spreads primarily through egg masses laid on surfaces including trees, vehicles, trailers, and rail cars. Egg masses resemble dried mud patches and are easily overlooked, allowing hitchhiking transport over long distances. The pest feeds on phloem tissue of many host trees including maples, oaks, elms, and dogwoods, producing copious honeydew that leads to sooty mold growth. While rarely killing mature trees, it causes significant aesthetic damage and is a serious pest of grapes.
Q: How should spotted lanternfly be managed on landscape trees?
A: For tree applications, systemic insecticides are preferred over foliar sprays due to drift concerns and application challenges on large trees. Imidacloprid and dinotefuran can be applied as soil drenches around the tree base or through trunk injection. These systemic products are taken up by the tree and affect the insects as they feed on phloem tissue. Contact insecticides like pyrethroids work well but are impractical for large tree canopies in most landscape settings. Destroying egg masses when found and monitoring for nymphs in spring are also important management tactics.
Q: Why is the invasive thrips species often misdiagnosed, and how can it be correctly identified?
A: This invasive thrips species causes damage that closely resembles broad mite injury, leading to frequent misdiagnosis. When treatments for mites fail to provide control, thrips should be suspected. The thrips are extremely small—only a couple of millimeters long—making visual detection difficult. They prefer feeding on new developing shoots and are particularly problematic on peppers and gardenias. Unlike broad mites, these thrips lay eggs in plant tissue, and pupae develop in the soil. Correct identification is important because mite treatments will not control thrips; effective products include spinosad, spinetoram (Xxpire), Mainspring, and Sarisa.
Q: How can pets contribute to the spread of boxwood blight in landscapes?
A: Cats and dogs moving through boxwood plantings can spread boxwood blight spores on their fur from infected plants to healthy ones. In research observations, a neighbor’s cat nicknamed “Vector” effectively spread the disease throughout a landscape by moving between infected and healthy boxwoods. When assessing boxwood blight risk, asking about pet access is essential—including whether neighbors have outdoor cats or dogs that might travel through the property. In managed landscapes where boxwood blight is being controlled with fungicides, restricting pet access to boxwood areas significantly improves disease management outcomes.
Q: What resources are available for staying updated on turf and ornamental pest issues in Georgia?
A: The UGA Turf and Ornamental Pest Management website offers a subscription service where professionals can sign up with their email to receive notifications about new blog posts and updates on insect pests, diseases, and weed science topics. This includes alerts about new pest detections, management recommendations, and research updates. The Georgia Pest Management Handbook, available online, provides current fungicide and pesticide recommendations. For specific diagnostic questions, samples can be submitted to the UGA Plant Disease Clinic, and both Dr. Williams-Woodward and Dr. Joseph are available via email for follow-up questions.
ADDITIONAL RESOURCES
Dr. Jean Williams-Woodward Contact:
Extension Plant Pathologist, University of Georgia Athens
Email available through UGA Extension
Dr. Shimat Joseph Contact:
Turfgrass and Ornamental Entomologist, University of Georgia
Turf and Ornamental Pest Management Blog: Available via QR code in presentation
Key References Mentioned:
- Georgia Pest Management Handbook (available online)
- Tennessee State University VSD Research
- Barnsley Gardens Boxwood Blight Case Study
- Georgia Department of Agriculture Spotted Lanternfly Updates
Products Mentioned:
- Fungicides: Propiconazole, Cevya (mefentrifluconazole), Postiva, Pentra-Bark adjuvant
- Insecticides: Spinosad, Xxpire, Acelepryn, Mainspring, Sarisa, imidacloprid, dinotefuran
- Biological: Bt kurstaki
For questions about plant diseases, contact Dr. Jean Williams-Woodward. For questions about insect pests, contact Dr. Shimat Joseph. All specialists are available via University of Georgia Cooperative Extension.
Processed for UGA Center for Urban Agriculture / GTBOP Archives