LAUREL WILT

Laurel wilt is a fungal disease that attacks the vascular system of woody plants in the Lauraceae family. Once infected, the tree rapidly wilts and dies, often in a matter of weeks. There are currently very few effective control measures beyond sanitation of affected material. A recent study suggests that approximately 300 million redbay trees have died due to the disease as of 2017.

 

DISEASE SYMPTOMS

  • Flagging of shoots near the apex of the tree
  • Leaves on flagged shoots rapidly brown, but do not abscise from shoots
  • Vascular discoloration

 

CAUSAL AGENT

The disease is caused by the ascomycete fungus Raffaelea lauricola.

 

HOST RANGE

  • Woody plants in the Lauraceae, a large family containing over 50 genera and 2500 species, including:
    • Avocado (Persea americana)
    • Redbay (Persea palustris)
    • Pondspice (Litsea aestivalis) (POPULATION THREATENED)
    • Pondberry (Lindera melissifolia) (POPULATION ENDANGERED)

 

GEOGRAPHIC DISTRIBUTION

Since the first detection of the disease in 2004 near the port of Savannah, Georgia, laurel wilt has spread rapidly across the Southern United States, and has been reported from 168 counties in nine states as of fall 2017. Based on genetic analyses, both Xyleborus glabratus and Raffaelea lauricola were introduced into the United States during a single event, and their populations seem to be native to parts of Asia.

 

SPREAD of the PATHOGEN and CONTROL OPTIONS

In Florida, the pathogen is spread by the introduced ambrosia beetle Xyleborus glabratus, which carries the fungus in specialized mouth pouches called mycangia. Other ambrosia beetles in the landscape carry R. lauricola in their mycangia, but may or may not spread the disease to new trees. In addition, the pathogen may spread between neighboring plants that have grafted roots. Rapid detection and destruction of infected plants is the most effective management option for trees in agricultural production. UF researchers are developing methods for exclusion of vectors by pheromones as well as testing efficacy of conventional and organic pesticides. Movement of infested firewood likely spread the vector and pathogen to new states and counties.

 

MORE RESOURCES

 

 

Prepared by Robin Choudhury, UF/IFAS Plant Pathology and EPI.