Speaker: Dr. David Coyle, Associate Professor, Department of Forestry and Environmental Conservation, Clemson University
Webinar Date: January 16, 2025
Duration: 52:19
NARRATIVE SUMMARY
Dr. David Coyle, a forest entomologist at Clemson University, delivered a comprehensive overview of landscape tree pests affecting the southeastern United States, emphasizing the critical distinction between invasive and native pest biology. He opened by explaining that invasive pests function as primary agents capable of killing healthy trees, while nearly all native pests are secondary organisms that respond to tree stress. This fundamental principle guided the entire presentation, with Dr. Coyle stressing that effective pest management requires understanding and addressing the underlying stress factors that make trees vulnerable.
The presentation covered environmental and anthropogenic stressors including extreme temperatures, drought, urban heat island effects, soil compaction, improper planting depth, and root damage from construction activities. Dr. Coyle used compelling examples, such as bald cypress planted in unsuitable urban environments far from their natural swamp habitats, to illustrate how site mismatches create chronic stress. He presented vivid imagery of the 2024 urban heat island effects and drought impacts across the Southeast, explaining how these stressors accumulate to compromise tree defenses.
Dr. Coyle systematically addressed major pest categories, beginning with common defoliators including forest tent caterpillar (Malacosoma disstria), which has caused significant outbreaks in the Beaufort-Savannah coastal region over the past three years, and eastern tent caterpillar (Malacosoma americanum). He explained that while these cyclical outbreaks are spectacular nuisances, established trees can typically survive one to three years of complete defoliation due to stored root reserves. Oak worms and other late-season defoliators received similar treatment, with Dr. Coyle emphasizing their role as indicators of tree stress rather than primary threats.
The ambrosia beetle discussion highlighted both native species and the invasive red bay ambrosia beetle, vector of laurel wilt disease (Raffaelea lauricola), which has devastated members of the Lauraceae family including red bay (Persea borbonia) and sassafras (Sassafras albidum) throughout the coastal plain. Dr. Coyle explained the symbiotic relationship between these beetles and their fungal associates, noting that fungicide injections with propiconazole remain the most effective management approach for high-value landscape specimens, though treatment must be repeated annually.
Bark beetle coverage featured extensive discussion of southern pine beetle (Dendroctonus frontalis), the region’s primary tree killer, contrasting its aggressive outbreak behavior with the more opportunistic Ips engravers. Dr. Coyle presented research demonstrating how healthy pines can resist beetle attacks through vigorous pitch responses, but stressed trees succumb rapidly. He provided diagnostic keys including the distinctive green needle drop caused only by southern pine beetle and the characteristic S-shaped galleries under bark.
The presentation’s major focus centered on invasive wood-boring beetles, particularly emerald ash borer (Agrilus planipennis), which Dr. Coyle identified as arguably the worst invasive forest pest of this generation. He detailed the insect’s biology, characteristic D-shaped exit holes, serpentine phloem galleries, and management strategies including trunk injections with emamectin benzoate. Dr. Coyle emphasized that ash trees can be saved if treated before losing thirty percent of canopy, though early detection remains challenging. Asian longhorned beetle (Anoplophora glabripennis), currently established in Charleston County, South Carolina, received detailed coverage including its preference for maples (Acer spp.) and the catastrophic structural damage caused by larvae boring deep into heartwood.
Dr. Coyle addressed newer invasive threats including crape myrtle bark scale (Acanthococcus lagerstroemiae), identifiable by its bright pink hemolymph when crushed, which has spread throughout the Southeast over the past twenty years. Management recommendations emphasized prevention through careful plant selection and properly timed systemic insecticide applications. Elm zigzag sawfly (Aproceros leucopoda) and spotted lanternfly (Lycorma delicatula), recently confirmed in Forsyth County, Georgia, were discussed as emerging concerns. Dr. Coyle noted that while spotted lanternfly populations can reach nuisance levels and impact vineyards and ornamental plantings, they remain manageable with available insecticides.
Throughout the presentation, Dr. Coyle emphasized practical management philosophy: prevention through appropriate species selection and site matching, maintaining tree health through proper cultural practices, early detection through regular monitoring, and realistic expectations regarding control options. He concluded with an extensive question-and-answer session addressing topics including Joro spider (Trichonephila clavata) management, elm zigzag sawfly spread potential, replanting intervals for pine regeneration, spotted lanternfly impacts on southeastern landscapes, and biological control prospects for crape myrtle bark scale.
YOUTUBE TIMESTAMPS
0:00 Introduction and Speaker Background
1:07 Welcome and Webinar Overview
1:19 Topic Introduction: Landscape Tree Pests
1:40 Critical Concept: Invasive vs. Native Pests
2:07 Native Pests as Secondary Stress Responders
2:22 Example: Bald Cypress Habitat vs. Urban Placement
3:00 Environmental Stressors: Temperature Extremes
3:23 Drought Monitor and Moisture Stress
3:58 Urban Heat Island Effects
4:42 Proper Planting Depth and Root Management
5:28 Avoiding Mulch Volcanoes
6:10 Construction Damage and Soil Compaction
7:18 Root Damage and Long-term Tree Decline
8:10 Environmental vs. Human-caused Stress Factors
8:29 Common Defoliators Introduction
8:40 Forest Tent Caterpillar Biology and Life Cycle
9:10 Egg Masses and Larval Behavior
9:22 Cyclical Outbreak Patterns
9:32 Tree Tolerance to Defoliation
9:53 Nuisance Issues During Outbreaks
10:05 Beaufort-Savannah Outbreak (2021-2024)
10:35 Aerial Imagery of Defoliation Patterns
11:21 Eastern Tent Caterpillar Comparison
12:08 Identification: White Stripe vs. Boot Prints
13:02 Fall Webworm Overview
14:08 Variable Moth Patterns and Distribution
14:41 Oak Worms: Late Season Defoliators
15:50 Treatment Decisions for Defoliators
17:25 Bagworm Biology and Host Range
18:42 Evergreen Bagworm Damage
20:15 Management Timing for Bagworms
23:30 Ambrosia Beetles: Regional Occurrence
23:45 Fungal Gallery Formation
24:00 Toothpick Frass Tubes on Hardwoods
24:40 Black Twig Borer and Branch Flagging
25:15 Red Bay Ambrosia Beetle Introduction
25:37 Laurel Wilt Disease and Lauraceae Family
26:03 Red Bay Decline Throughout Coastal Plain
26:27 Management Options: Fungicide Injections
27:02 Bark Beetles: Native Species Overview
27:08 Southern Pine Beetle: Primary Tree Killer
27:43 Geographic Range and Risk Assessment
28:00 Diagnostic Sign: Green Needle Drop
28:16 Pitch Tubes and Attack Patterns
28:40 S-shaped Galleries Under Bark
29:02 Ips Bark Beetles: Opportunistic Attackers
29:18 Ips vs. Southern Pine Beetle Behavior
29:49 Spotty Damage Patterns with Ips
30:35 Turpentine Beetles and Pitch Response
31:11 Research on Healthy Tree Resistance
32:15 Pine Sawyers as Late-succession Species
33:10 Bark Beetle Management: Tree Health Focus
34:24 Jewel Beetles and Flat-headed Borers
34:33 Emerald Ash Borer: Worst Invasive of Generation
34:56 Life Cycle and Phloem-feeding Larvae
35:16 Distribution Across Eastern North America
35:27 Diagnostic Symptoms: Crown Decline
35:42 Epicormic Sprouting: “Soul of the Tree Leaving”
36:04 Management Decision: Remove and Replace
36:13 D-shaped Exit Holes and Winding Galleries
36:28 Woodpecker Blonding on Infested Trees
36:54 Saving Ash Trees: 30% Canopy Threshold
37:32 Chemical Control Options: Emamectin Benzoate
37:57 Cerambycids and Round-headed Borers
38:04 Asian Longhorned Beetle Introduction
38:15 Wide Host Range: Preference for Maples
38:39 Egg Niches and Phloem Feeding
38:47 Larvae Boring into Heartwood
39:00 Structural Damage and Branch Failure
39:20 Charleston County, SC Population
40:51 Crape Myrtle Bark Scale Overview
41:04 Scale Feeding and Sooty Mold Production
41:22 Identification: Bright Pink Hemolymph
41:41 Distribution Throughout Southeast
42:00 Management: Prevention and Systemics
42:27 Spotted Lanternfly: New to Georgia
42:43 Life Cycle and Host Range
43:02 Tree of Heaven Preference
43:16 Elm Zigzag Sawfly Introduction
43:33 Distinctive Zigzag Feeding Pattern
43:59 Complete Defoliation Potential
44:28 Management with Insecticides
45:00 Joro Spider Brief Discussion
45:46 Q&A Session Begins
46:14 Q: Preventing Joro Spiders
46:53 Q: Elm Zigzag Sawfly Spread Prognosis
47:27 Q: Replanting Intervals for Pines
48:06 Regeneration Weevils and Nantucket Pine Tip Moth
48:22 Pre-treated Seedlings Recommendation
48:43 Q: Spotted Lanternfly Impact Concerns
48:51 Forsyth County, Georgia Population
49:00 Management Feasibility and Expectations
50:32 Q: Systemic Treatment Duration for Seedlings
51:22 Q: Biological Control for Crape Myrtle Bark Scale
51:45 Research on Ants and Lacewings
52:00 Host Specificity Challenges in Biocontrol
52:13 Closing Remarks and Thank You
QUESTIONS & ANSWERS
Q: What is the fundamental difference between invasive and native tree pests in terms of their behavior?
A: Invasive pests function as primary agents, meaning they can attack and kill healthy, vigorous trees regardless of the plant’s condition. In contrast, nearly all native pests in our region are secondary organisms that respond to stress in trees. For native pests, the underlying issue is almost always tree stress from environmental factors, site conditions, or management practices rather than the pest itself.
Q: Can established trees survive complete defoliation from native pest outbreaks like forest tent caterpillar?
A: Yes, established trees with healthy root systems can typically survive one, two, or even three consecutive years of complete defoliation because they have substantial energy reserves stored in their roots. However, recently transplanted trees, trees in roadway medians, or those already under stress are much more susceptible to mortality. While native defoliators are massive nuisances during outbreak years, they usually don’t kill well-established landscape trees.
Q: What is laurel wilt disease and how is it managed?
A: Laurel wilt is a devastating vascular disease caused by the fungus Raffaelea lauricola, which is transmitted by the invasive red bay ambrosia beetle. The disease affects members of the Lauraceae family including red bay, sassafras, and other laurel relatives. Management options are limited—cutting down and chipping infected trees, or for high-value landscape specimens, annual fungicide injections with propiconazole. Insecticides aren’t practical because the beetles fly practically year-round in the coastal plain.
Q: How can you tell if you have southern pine beetle versus other bark beetles?
A: The most diagnostic sign of southern pine beetle is green needles dropping from the tree—it’s the only bark beetle that causes pines to drop green needles. You’ll also see pitch tubes in bark crevices where the tree tried to fight off the beetles. Under the bark, southern pine beetle creates distinctive S-shaped galleries, whereas Ips beetles create Y-shaped or H-shaped patterns. Southern pine beetle attacks the entire tree simultaneously, causing uniform color change, while Ips damage appears spotty.
Q: Can ash trees be saved from emerald ash borer, or is removal the only option?
A: Ash trees can be saved if caught early enough—specifically, if they have lost less than thirty percent of their canopy. Treatment involves trunk injections or soil drenches with emamectin benzoate or similar systemic insecticides. However, once a tree has lost more than thirty percent of its canopy to emerald ash borer, saving it becomes an uphill battle. The challenge is that trees often look healthy while already heavily infested, making early detection difficult.
Q: What makes Asian longhorned beetle such a serious threat to landscape trees?
A: Asian longhorned beetle attacks a wide range of hardwoods, with a strong preference for maples in our region—approximately ninety-eight percent of attacks occur on maple species. The larvae bore deep into the heartwood of the tree, creating extensive tunnels that structurally weaken the tree and lead to branch failure. Unlike phloem-feeding insects, this heartwood damage is irreversible and can cause catastrophic tree failure. The beetle is currently established in Charleston County, South Carolina.
Q: How do you identify crape myrtle bark scale?
A: Crape myrtle bark scale appears as white, felt-like encrustations on crape myrtle bark. The definitive identification method is to crush one—if you get bright pink hemolymph (insect blood), you’ve confirmed crape myrtle bark scale. The scales feed by inserting their mouthparts like a straw and sucking plant fluids, then excrete honeydew (sugar water) which leads to black sooty mold growth on leaves, bark, and anything underneath the tree.
Q: What management options exist for crape myrtle bark scale?
A: Prevention is the best approach—don’t purchase or plant infested material, and diversify plantings rather than relying solely on crape myrtles. For chemical management, foliar sprays must be timed to target the crawler stage before scales settle and form their protective waxy covering. Soil-applied systemic insecticides work very well and provide season-long control. Research is ongoing regarding biological control with natural enemies, but current options are limited.
Q: Should homeowners be concerned about spotted lanternfly now that it’s confirmed in Georgia?
A: Spotted lanternfly has been confirmed in Forsyth County in the Atlanta area, and populations will likely continue to spread. They are extremely annoying when present in high numbers and can impact vineyards, fruit trees, and ornamental plantings. However, they’re not invincible—various insecticides provide effective control. If you get them on your property, expect to put in effort to manage them, but they are manageable. They’re more of a significant nuisance pest than a catastrophic threat in our region.
Q: What precautions should be taken when replanting pines after harvest?
A: Newly planted pines are susceptible to regeneration weevils and Nantucket pine tip moth. The most cost-effective approach is purchasing seedlings that are pre-treated with systemic insecticide—these cost only a few cents more per seedling but provide one to two years of protection. From a forestry perspective, waiting six to eight months after harvest before replanting allows time for natural enemies to establish and for leftover roots to degrade, reducing pest pressure.
Q: Is biological control a viable option for managing crape myrtle bark scale?
A: Biological control research is currently underway, with studies examining whether ants and lacewings might provide effective control. However, there’s a significant challenge with biocontrol for scale insects—there are so many different scale species in the landscape that unless you have an agent highly specific to crape myrtle bark scale, predators will simply feed on whatever scales are available rather than focusing on the target pest. This lack of host specificity makes developing effective biological control difficult.
Q: Can Joro spiders be prevented from establishing in an area?
A: No, there’s no practical way to prevent Joro spiders from establishing in an area. If they’re not already present, they will likely arrive eventually. They prefer structures like houses, decks, carports, and porches, which is why they’re so noticeable. While you can remove individual webs and spiders from your immediate property as a hobby, once they establish in a general area, they’re there to stay. Prevention on a large scale is not feasible.
ADDITIONAL RESOURCES
Speaker Contact:
Dr. David Coyle
Associate Professor, Department of Forestry and Environmental Conservation
Clemson University
Email: [Contact through Clemson University Extension]
Key References:
- Emerald Ash Borer Management Guide (comprehensive chemical control options)
- Southern Pine Beetle Prevention and Management (UGA/Clemson Extension)
- Laurel Wilt Disease Information (USDA Forest Service)
- Crape Myrtle Bark Scale Management (Multiple State Extension Services)
Pest Identification Resources:
- Forest tent caterpillar: Distinguished by “footprint” markings, no tent construction
- Eastern tent caterpillar: White dorsal stripe, constructs tents in branch crotches
- Southern pine beetle: S-shaped galleries, green needle drop
- Ips: Y or H-shaped galleries, spotty tree damage
- Emerald ash borer: D-shaped exit holes, serpentine galleries, ash hosts only
- Asian longhorned beetle: Round exit holes, preference for maples, large white spots
- Crape myrtle bark scale: Bright pink hemolymph when crushed
Reported Pest Sightings:
- iNaturalist for documenting invasive species observations
- State extension services for confirmed pest identifications
- USDA APHIS for regulated pest detections
For questions about forest and landscape tree health, contact your local Extension office or visit Clemson University Extension’s website.