July 18, 2024 | Dr. Karla Addesso, Tennessee State University
CEU Categories: Category 24 (Ornamental and Turf), Category 35 (Industrial, Institutional, Structural)
Duration: 53:37
SUMMARY
Dr. Karla Addesso provides comprehensive guidance on Chrysobothris flathead borers, native beetles causing significant damage to nursery and landscape trees. Over 140 species exist in North America, many nearly impossible to distinguish visually. The presentation covers innovative identification methods including genetic analysis and spectral imaging. Life cycle features mid-May emergence (580-600 growing degree days), invisible damage until fall, and preference for drought-stressed transplants. A groundbreaking finding involves larvae in California pear fruit—unprecedented host shift potentially driven by drought. Management emphasizes irrigation as remarkably effective, with watered transplants showing very low attacks without insecticides. Imidacloprid drenches remain best chemical option (three years protection). Alternative strategies include purple trunk traps, cover crops, avoiding herbicide drift, and preserving parasitic wasp natural enemies.
KEY TIMESTAMPS
0:00 Introduction and Speaker Background
4:09 Flathead Borer Overview and Chrysobothris Focus
6:41 Life Cycle and Seasonal Timing
8:52 When Damage Becomes Visible
11:05 Most Susceptible Trees
12:29 Species Identification Challenges
15:06 Morphological and Genetic Methods
20:33 California Pear Fruit Discovery
24:27 Chemical Communication and Wax Profiling
28:22 Scouting and Monitoring Strategies
29:46 Purple Sticky Traps
30:44 Trunk Mimic Traps vs Panel Traps
32:52 Growing Degree Day Models
36:02 How Small of Tree Will They Attack?
37:44 Herbicide Drift Stimulates Attacks
39:08 Imidacloprid Systemic Drenches
41:00 Alternative Products: Acelepryn and Mainspring
44:14 White Latex Paint for Orchards
45:00 Weeds and Cover Crops Provide Protection
47:32 Irrigation: Unexpected Effectiveness
48:42 Natural Enemies: Parasitic Wasps
50:06 Summary and Take-Home Messages
52:05 Q&A: Imidacloprid Availability
KEY TAKEAWAYS
Identification: 140+ Chrysobothris species; requires expert dissection or genetic tools; host-specific behavior varies by species
Timing: Mid-May emergence in Tennessee (earlier south, later north); use 580-600 GDD (base 50°F) for prediction
Vulnerable Trees: Newly transplanted, drought-stressed, mechanically injured, or grafted trees; southwest-facing trunk sides
Most Effective Management: Irrigation during establishment year dramatically reduces attacks; imidacloprid drench at transplant gives 3-year protection
Non-Chemical Options: Cover crops or weeds shade trunks; white paint for orchards; maintain plant health; avoid herbicide drift
Monitoring: Purple trunk mimic sticky traps work better than panels; placement in full sun
Natural Control: Parasitic wasps provide biocontrol; judicious insecticide use preserves beneficials
QUESTIONS ANSWERED
Q: Why is species identification so difficult?
A: Over 140 similar-looking species require expert genitalia dissection or genetic analysis; females often indistinguishable; what we call “flathead apple tree borer” is actually a species complex.
Q: What was discovered in California pear orchards?
A: Chrysobothris larvae found in fruit for first time ever—previously only fed under bark; adults successfully emerged from fruit; potential host shift driven by drought stress; could transform ornamental pest into crop pest.
Q: What is the single most effective management practice?
A: Irrigation. Research showed irrigated transplants had very low beetle attacks without insecticides; explains why container production sees fewer problems; drought stress produces chemical signals attracting beetles.
Q: Does herbicide use affect borer attacks?
A: Yes, significantly. Accidental glyphosate overspray on trunks stimulates attacks; beetles can smell herbicide-treated trees; careful application essential around valued plants.
Q: What about imidacloprid concerns?
A: Still most effective treatment (3-year protection); read labels for flowering tree restrictions; alternatives (Acelepryn, Mainspring) show variable results; trunk sprays require monthly applications; non-chemical options increasingly viable.
Full archive summary with 88 detailed timestamps and extended Q&A: [GTBOP Website Link]
Speaker: Dr. Karla Addesso, Associate Professor of Entomology, Tennessee State University Nursery Research Center, McMinnville, TN
Funding: USDA NIFA and Southern SARE
Resources: Southeastern U.S. Pest Control Guide (NC State Extension)