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  • HOME
  • About
    • Benefits of Membership
    • Renew or Join
    • Officers
    • History of SE-ARS
    • HELP: How to use our website
    • 2012 ARS/ASA Convention
    • Contact Us
    • Events >
      • Upcoming & Past Events >
        • Calendar View
      • Flower Show Information >
        • 2018 Flower Show
        • 2017 Flower Show
        • 2016 Flower Show
        • 2015 Flower Show
        • 2014 Flower Show
  • BRR
  • Info
    • Dexter Study Group >
      • Don Kellam
    • Plant Sources
    • "Good Doers"
    • How to plant and care for a rhododendron
    • Rhododendron diseases & pests
    • How to propagate rhododendrons
    • How to hybridize rhododendrons
    • Other rhododendron links
    • Rhododendrons for Upstate South Carolina
    • RhodoWeather
    • ARS Blog
    • Hooper Bald
    • Rosebay
  • Photos
    • 2019 ASA CONVENTION
    • 2020 Virtual Flower Show
    • New Hybrids
    • Submit Photos
    • 2015 Photo Contest
    • General Gallery
    • Featured Rhodos >
      • Red R. maximum
      • R. hyperythrum
  • Members
    • Join or Renew >
      • Mail Application
    • Plant Payment
    • Gardens
    • JOURNAL ARS
    • Custom Search
    • SE-ARS Board Minutes (log in)
    • SE-ARS Member and Assoc Roster (log in)
    • Treasurer's Report 2016-24 >
      • Treasurer's Reports 2015 (log in) >
        • Treasurer's Reports 2014 (log in)
    • SE-ARS Meeting Minutes
Rhododendron Books
Compendium of Rhododendron Diseases, APS

Rhododendron Diseases and Pests

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Winter (cold, wind and sun) damage
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        Rhododendrons are relatively disease free when planted properly and provided adequate but not excessive water.    If disease trouble does develop, the following links may be helpful:
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​       Clemson University, S.C.:

                Clemson University Extension Service diseases
                Clemson University Extension Service insects
     
           Connecticut (Dr. Sharon Douglas):
                 List of Common Diseases and Insect Pests of Rhododendrons
                 Common Problems of Rhododendrons and Azaleas
                 Rhododendron Tissue Proliferation
                 Winter Injury and Drying of Rhododendrons



            University of Maryland:
                 Rhododendron and Azalea Diseases






The Azalea/Rhododendron Stem Borer (Oberea myops) and Rhododendron Borer (Synanthodon rhododendri) are common pests in our area, endemic in wild populations, affecting rhododendrons, azaleas, mountain laurels and other ericaceous plants.
Control is most effective by frequently monitoring plants for wilted stems, which should be promptly cut off below the infestation.   If the borer tunnel is below the wilted stem, injecting the tunnel with WD40 (which displaces water from the borer larva) may kill the larva and arrest the damage.              
      Natural History and Recommendations for Control of the Rhododendron Stem Borer, Oberea Myops.  Culin, Gorsuch, Pizzuto, Clemson University
      



Rhododendron stem borer, Oberea myops.
Small, thin longhorned beetles feed on the undersides of leaves at the midvein causing the leaf to curl abnormally. Females lay eggs in new shoots just below the bud in late June to early July. Larvae bore into the twig and most likely overwinter there. The second year, the larva continues boring downward and spends the second winter in the roots. This year many holes are made to remove frass from the tunnel and "sawdust" gathers on the ground around the stem. At maturity, the creamy white larva is 1" long. When needed, permethrin, one of the products registered for use against this pest in Connecticut, applied to the stems from late May through mid-June, should control this pest. Consult the label for dosage rates and safety precautions. Alternatively, prune out and dispose of infested shoots.           (University of Connecticut)
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Joseph D. Culin, Clyde S. Gorsuch, Theresa M. Pizzuto Department of Entomology, Clemson University
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Joseph D. Culin, Clyde S. Gorsuch, Theresa M. Pizzuto Department of Entomology, Clemson University
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Joseph D. Culin, Clyde S. Gorsuch, Theresa M. Pizzuto Department of Entomology, Clemson University


Rhododendron Borer, Synanthedon rhododendri
Recognition and Life Cycle
The adults of this pest are day-flying moths that resemble wasps or yellow jackets. They are approximately 1/4-inch long, making them the smallest clear-wing borer. The wings are mostly clear, and the body is black with three yellow abdominal bands. Adults appear in late-May into June and females lay eggs on the twigs. Upon hatching, the small grub-like caterpillars, with white bodies and dark heads, bore into the inner bark, and later the sapwood, of the main stems and branches. This pest overwinters in the burrows as an inch long mature larva. There is one generation per year.       (University of Conn.)
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Univ. Massachusetts
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Univ. Massachusetts
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https://www.butterfliesandmoths.org/species/Synanthedon-rhododendri
RHODODENDRON BORER: A WORTHY COMPETITOR
John W. Neal, Jr.
Florist and Nursery Crops Laboratory
USDA, SE, ARS Beltsville, Maryland
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Hi All,
The Scentry Rhododendron Borer lures used with the sticky wing traps ended the borer problem I had several years ago.  The lures attact and trap the males to interrupt the breeding cycle.  It is non-toxic.  I used the traps for several years in a row, but haven't used them for a number of years now and the problem has not showed up again.  They are advertised to be used for monitoring so you know when to spray, but I never did spray and the traps & lures alone took care of it.  
Vivian Abney
East Fork Nursery

Comment:
The Scentury Rhododendron Borer lures noted above would be expected to apply only to the Rhododendron Borer,  Synanthedon rhododendri, a small clearwing moth, and not to Oberea myops, the Rhododendron Stem Borer, a small longhorn beetle.
Larvae of both borers produce similar damage to plants (wilting, tunnels and frass) which may be controlled mechanically by cutting below the tunneled stem.   (JHMcC)

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Lichen on old branches: Not a disease.   Austin Hagan,Extension Plant Pathologist,Professor, Plant Pathology, Auburn University.

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Click on image for more information
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Steve D. Pettis 
Commercial and Consumer Horticultural Agent
NC State Extension, Henderson County Center, 100 Jackson Park Rd., Hendersonville, N.C.
"Rhododendron sp. Plant Diseases"
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Cranberry Rootworm Beetle
    Thanks to Rick Ellis, Charlotte, NC for drawing attention to this pest, which has been recognized in the Charlotte area for at least 10 years.
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Click on image for information
Phytopthera ramorum (sudden oak death) West Coast plants caution
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