Sudden Oak Death and Laurel Wilt:

Emerging Plant Pathology Problems of Woody

Ornamentals-North and Central Florida

Carrie Lapaire Harmon

UF/IFAS-SPDN

4-08

P. ramorum Status• 2006, DPI find plants of 5 species of Camellia infected with P.

ramorum at 2 nurseries.• 2006, Clemson researchers isolate P. r. from water at one of the

positive nurseries. Additional sampling has not recovered the pathogen

• Florida trace surveys found no additional FL nurseries infected.• Additional hosts of interest: Osmanthus, Prunus, Rosa rugosa,

others• 2007, DPI finds camellias in a North FL nursery for the second year

in a row. The nursery is conducting eradication efforts in tandem with DPI.

• An infected plant from this nursery is found in a landscape setting and is eradicated, along with some soil.

Environmental Impact

• Although there have been positive finds in landscapes, there are no detections currently known to be infected in natural areas.

• The pathogen has been isolated from water from a nursery; the pathogen could easily move in our streams, springs, and groundwater.

• If this disease were to become established in natural areas, several of our native plant species are listed as possible hosts.

• Hosts of concern remain those in nurseries and landscape environments; areas surrounding nurseries are inspected as well.

Phytophthora ramorum: associated symptoms

• Two syndromes caused by this pathogen– Leaf and twig blight

• Leads to leaf drop and general dieback

– Trunk, branch, and bark canker• Disease progresses under the bark, disrupts

vascular movement of xylem and phloem – kills the host by clogging up the pathways for movement of water and nutrients – this is why the symptoms include wilting

• Cankers occasionally will bleed plant sap – not always

Phytophthora ramorum: associated symptoms

• Hosts of immediate importance to Florida:– Camellia, azalea exhibit leaf and twig

blight

– Viburnum also exhibits bark canker (sometimes bleeding) followed by wilt and death

What’s FL doing about it?• FDACS, DPI continue to survey nurseries every year• DPI and IFAS are working together to try to identify if

there are diseased plants in the FL landscape• Still collecting samples any symptomatic host,

especially: camellia, viburnum, rhododendron of CA origin 4 years old or newer exhibiting dieback, leaf blight

• Remove a small twig with a few leaves and place it in a zip-top bag. Take the sample to your extension agent and ask them to submit it to GNV.

Hosts summary

• Many more than 100 species Approximately 2/3 exhibit leaf and stem blight and sporulate

• Approximately 1/3 exhibit stem and bole canker and do not sporulate

• Complete list in handout

Ramorum blight: camelliaRamorum blight: camellia

Ramorum blight: camelliaRamorum blight: camellia

SOD: oak hostsSOD: oak hosts

Contact information

Richard Cullen, DiagnosticianRichard Cullen, DiagnosticianPlant Disease ClinicPlant Disease ClinicBldg 78 Mowry Rd., University of FloridaBldg 78 Mowry Rd., University of FloridaGainesville, FL 32611Gainesville, FL 32611

Phil Harmon, Extension Pathologist:Phil Harmon, Extension Pathologist:UF-IFAS Department of Plant PathologyUF-IFAS Department of Plant Pathology1453 Fifield Hall, Gainesville, FL 326111453 Fifield Hall, Gainesville, FL 32611

New Disease of Red Bay/Laurel• Host is Persea borbonia, an important species for

wildlife• Associated with an exotic ambrosia beetle,

Xyleborus glabratus, and caused by a new fungus, Raffaelea laurelensis

• Wilted foliage, vascular discoloration, sawdust tubes

• Other Lauraceae, including Sassafras albidum, Lindera benzoin, and Persea palustris are killed when artificially inoculated

• Coastal locations in FL, GA, and SC

Red bay, Persea borbonia, is a significant component of forest ecosystems in the southeastern US. It has been decimated by laurel wilt.

Distribution and Additional Info

• Attacks seemingly healthy trees; beetle may be attracted to stressed trees

• Leads to wilt and death• Redbay and sassafras mortality in SC, GA and FL • Mortality in Florida since detection increased from 10 to

60% in 9 months• Several Laurel relatives susceptible, including pondspice,

avocado, sassafrass, and pondberry/southern spicebush (federally endangered species)

• New name is Laurel Wilt Disease• Similar to another devastating tree wilt disease: Dutch Elm

Disease

FL counties with Laurel Wilt

• Duval (2004)• Baker (2006)• Bradford (2006)• Clay (2006)• Nassau (2006)• St. Johns (2006)• Indian River (2006)• Putnam (2007)

Wilt, Vascular Discoloration

Signs of the Beetle

Picture credits: Albert E. Mayfield III, and M. C. Thomas, FDACS/DPI

Avocado

• Research at the UF-TREC in Homestead and DPI quarantine facilities in GNV has resulted in data on susceptible cultivars of avocado: ‘Brogdon’ was highly, ‘Simmonds’ moderately, and ‘Reed’ slightly susceptible.

• In September 2007, the first

landscape avocado plant

succumbed to

the disease in Jacksonville.

‘Simmonds” avocado 20 days after inoculation, DPI

What can we do about it?• By the end of 2006, the disease had spread to 5 counties

in SC, 15 in Georgia, and 8 in FL• Now there are more than 30 counties with infected trees• Currently, there is no method to halt or even slow the

spread of this disease– The beetle is a powerful flier– By the time symptoms appear, the beetle has infected many trees

in the area– Pesticide use is not recommended due to the numerous off-target

species that would be affected– Biological controls are not known at this time– Human movement of infested plant material is aiding the long-

distance spread of the vector.

• Two experiments in process: sanitation (cutting out all dead or dying trees) and fungicide/insecticide injections

You can help

Encourage others to collect red bay seeds. It is possible that some germplasm will be resistant to the disease. (note the forms included in the handouts)

Remind people not to transport mulch, firewood, etc.

Direct people to the Forest Health Protection site: http://www.fs.fed.us/r8/foresthealth/laurelwilt/index.shtml

Images from http://www.fs.fed.us/r8/foresthealth/laurelwilt/gallery/gallery_host_plants.shtml

Contact information

Bud Mayfield, Forest Entomologist:Bud Mayfield, Forest Entomologist:Florida Department of Agriculture and Consumer Services, Florida Department of Agriculture and Consumer Services, Division of ForestryDivision of ForestryPO Box 147100 Gainesville, FL 32614-7100PO Box 147100 Gainesville, FL 32614-7100

Randy C. Ploetz, ProfessorIFAS, Tropical Research and Education Center, Plant Pathology Department, Homestead, Florida

Jason Smith, Assistant ProfessorIFAS, Dept. of Forestry and ConservationGainesville, FL