1. A new threat to California avocado industry
Laurel Wilt Disease
A new threat to California avocado industry
Akif Eskalen, Ph.D.
Asst. Cooperative Extension Specialist / Plant Pathologist
Department of Plant Pathology and Microbiology
University of California, Riverside
Laurel Wilt module courtesy of Akif Eskalen, UC Riverside

2. Causal agent
It is an Ophiostoma fungus, Raffaelea lauricola similar to the Dutch Elm Disease.
Pictures from: Fraedrich et al. 2008
Slide courtesy of Akif Eskalen, UC Riverside

3. Coleoptera, Curculionida
The fungus is believed to have arrived with an Asian origin redbay ambrosia beetle Xyleborus glabratus, Eichhoff, 1877
Coleoptera, Curculionida
1/16 inch-long
Pictures from: Albert E. Mayfield
Slide courtesy of Akif Eskalen, UC Riverside

4. How did they get here?
The redbay ambrosia beetle likely arrived in solid wood packing material, such as crates or pallets.
Pictures from: Albert E. Mayfield
Like many other non-native wood-boring beetles
SWPM is routinely used to ship goods internationally, but these materials can harbor unwanted wood-inhabiting pests if they are not properly treated before export.
Slide courtesy of Akif Eskalen, UC Riverside

5. How does the disease spread?
The pouches or mycangia (arrows) in the head of a red bay ambrosia beetle, where the wilt fungus is carried
(Photo by Mike Ulyshen).
they feed on the fungi growing on the wood.
Slide courtesy of Akif Eskalen, UC Riverside Source:

6. How does the disease spread?
 Most likely the result of human transport of infested wood, either from Asia as a separate, new introduction or from previously infested areas in the southeastern United States.
Source:
Photo by: T. Coleman
Slide courtesy of Akif Eskalen, UC Riverside

7. Trees in the Lauraceae Avocado Bay Laurel California Bay Laurel Redbay
Persea americana
Bay Laurel
Laurus nobilis
California Bay Laurel
Umbellularia californica
Redbay
Persea borbonia
Camphor tree
Cinnamomum camphora
Sassafras
Sassafras albidum
Silk bay
Persea humilis
Northern Spicebush
Lindera benzoin
Lancewood
Ocotea coriacea
Swamp bay
Persea palustris
Love vine, Devil’s gut
Cassytha filiformis
Pepperleaf sweetwood
Licaria triandra
Pondspice
Litsea aestivalis
Slide courtesy of Akif Eskalen, UC Riverside

8. Distribution of California Bay laurel in California
It has been shown that the native California bay laurel is susceptible to this disease. Thus, it is highly probable that the disease will establish in California if the beetle spreads into the western United States.
Slide courtesy of Akif Eskalen, UC Riverside
Photo from: San Francisco State University Department of Geography
by  Alicia Mariscal, student in Geography 316, Fall 2001

9. Symptoms on Redbay Slide courtesy of Akif Eskalen, UC Riverside
Photo by: A.Eskalen
Slide courtesy of Akif Eskalen, UC Riverside

10. Sapwood symptom on Redbay
Slide courtesy of Akif Eskalen, UC Riverside
Picture from: Fraedrich et al. 2008

11. Sapwood symptom on Redbay
Photo by: A.Eskalen
Slide courtesy of Akif Eskalen, UC Riverside

12. Symptom on Sassafras healthy infected Dead Row of Sassafras
Photos by: A.Eskalen
Slide courtesy of Akif Eskalen, UC Riverside

13. Geographical distribution of Laurel Wilt
Miami Dade county
Slide courtesy of Akif Eskalen, UC Riverside

14. Laurel wilt disease on avocado
Insect live in woody tissues and distribute the disease.
Recently a new avocado wilting disease was reported in Florida which is also known as laurel wilt disease caused by a Raffaelea laurelensis. Laurel wilt is a vascular disease of redbay (Persea borbonia (L.) Spreng.) and other plants in the family Lauraceae. The fungus is vectored by a non-native insect of Asian origin, the redbay ambrosia beetle (Xyleborus glabratus Eichhoff). (Mayfield et al. 2008; Fraedrich et al. 2008; Kubono and Ito, 2002).
Avocado (Persea americana)
(Ploetz and Pena, 2007)
Slide courtesy of Akif Eskalen, UC Riverside

15. Laurel wilt disease on avocado in Florida
Laurel wilt disease caused by Raffaelea sp. on backyard avocado trees in Florida
February 2009, Savannah/Florida
Photo by: A.Eskalen
Slide courtesy of Akif Eskalen, UC Riverside

16. Laurel wilt disease on avocado in Florida
Photos by: A. Eskalen
Laurel wilt disease caused by Raffaelea lauricola on backyard avocado tree in Florida
Slide courtesy of Akif Eskalen, UC Riverside

17. What to do?
If the tree is wilted in a large proportion of its crown, and has black discoloration in the sapwood, it is likely infected with the laurel wilt fungus. Notify your local county agent for confirmation
Slide courtesy of Akif Eskalen, UC Riverside
Photos by: A.Eskalen

18. Acknowledgements
California Avocado Commission & Avocado growers Virginia McDonald Shannon C. Lynch Ben Faber Gary Bender Mary Bianchi From University of Florida Randy Ploetz Jonathan Crane Jorge Pena
Slide courtesy of Akif Eskalen, UC Riverside