Laurel wilt
Encyclopedia
Laurel wilt, also called laurel wilt disease, is a vascular disease of the Lauraceous plant caused by the fungus Raffaelea lauricola and transmitted by the invasive
redbay ambrosia beetle
, Xyleborus glabratus
. The disease affects and kills members of the laurel family
. The avocado
is perhaps the most commercially-valuable plant affected by laurel wilt.
and Georgia
, and notably in Florida
, where it has reached as far south as Okeechobee County and as far west as Columbia County
. The redbay ambrosia beetle was discovered in Savannah, Georgia
's Port Wentworth area in spring 2002; however, it is likely to have been established in the area prior to 2002 when the three adult specimens were trapped at the port. The beetle likely entered the country in solid wood packing material with cargo that was imported at Port Wentworth. Redbay trees began dying in Georgia and South Carolina near the Savannah area in 2003. By early 2005, officials with the Georgia Forestry Commission (GFC), South Carolina Forestry Commission (SCFC), and USDA Forest Service began to suspect the newly discovered ambrosia beetle was associated with this mortality.
borbonia), a tree particularly abundant in maritime forests of Georgia, South Carolina and Florida, has been the primary species affected by the wilt. Sassafras, a less common tree in the coastal plains of the Southeast but with a more extensive range than redbay, has also been affected by the disease but to a lesser extent than redbay. The wilt fungus has also been isolated from dead and dying pondspice (Litsea aestivalis) and pondberry (Lindera melissaefolia), however the redbay ambrosia beetle has not been found in either of these species. Pondberry is a federally endangered species while pondspice is regarded as a threatened or endangered species in some southeastern states.
It is important to note that while this fungicide may be useful in protecting some trees against the wilt, this fungicide is NOT cleared for use on fruit trees that are part of commercial production for human consumption.
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
redbay ambrosia beetle
Ambrosia beetle
Ambrosia beetles are beetles of the weevil subfamilies Scolytinae and Platypodinae , which live in nutritional symbiosis with ambrosia fungi and probably with bacteria...
, Xyleborus glabratus
Xyleborus glabratus
The redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is a type of ambrosia beetle recently invasive to United States. It has been documented as spreading laurel wilt, a fungus that can kill several trees in the Lauraceae family ....
. The disease affects and kills members of the laurel family
Lauraceae
The Lauraceae or Laurel family comprises a group of flowering plants included in the order Laurales. The family contains about 55 genera and over 3500, perhaps as many as 4000, species world-wide, mostly from warm or tropical regions, especially Southeast Asia and South America...
. The avocado
Avocado
The avocado is a tree native to Central Mexico, classified in the flowering plant family Lauraceae along with cinnamon, camphor and bay laurel...
is perhaps the most commercially-valuable plant affected by laurel wilt.
Symptoms
Symptoms of laurel wilt include wilted stems and leaves, black streaking in the wood, and strings of compacted sawdust protruding from tree trunks. Laurel wilt can spread in at least two ways: one is via the beetle's natural reproduction and migration. A second way is through the sale and transport of beetle-infested wood, a result of redbay's use as firewood and for outdoor grilling.History
Laurel wilt has been found in South CarolinaSouth Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
and Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
, and notably in Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, where it has reached as far south as Okeechobee County and as far west as Columbia County
Columbia County, Florida
Columbia County is a county located in the U.S. state of Florida. As of 2000, the population was 56,513. The U.S. Census Bureau 2005 estimate for the county is 64,040 . Its county seat is Lake City, Florida....
. The redbay ambrosia beetle was discovered in Savannah, Georgia
Savannah, Georgia
Savannah is the largest city and the county seat of Chatham County, in the U.S. state of Georgia. Established in 1733, the city of Savannah was the colonial capital of the Province of Georgia and later the first state capital of Georgia. Today Savannah is an industrial center and an important...
's Port Wentworth area in spring 2002; however, it is likely to have been established in the area prior to 2002 when the three adult specimens were trapped at the port. The beetle likely entered the country in solid wood packing material with cargo that was imported at Port Wentworth. Redbay trees began dying in Georgia and South Carolina near the Savannah area in 2003. By early 2005, officials with the Georgia Forestry Commission (GFC), South Carolina Forestry Commission (SCFC), and USDA Forest Service began to suspect the newly discovered ambrosia beetle was associated with this mortality.
Consequences
The redbay (PerseaPersea
Persea is a genus of about 150 species of evergreen trees belonging to the laurel family, Lauraceae. The best-known member of the genus is the avocado, P. americana, widely cultivated in subtropical regions for its large, edible fruit.-Overview:...
borbonia), a tree particularly abundant in maritime forests of Georgia, South Carolina and Florida, has been the primary species affected by the wilt. Sassafras, a less common tree in the coastal plains of the Southeast but with a more extensive range than redbay, has also been affected by the disease but to a lesser extent than redbay. The wilt fungus has also been isolated from dead and dying pondspice (Litsea aestivalis) and pondberry (Lindera melissaefolia), however the redbay ambrosia beetle has not been found in either of these species. Pondberry is a federally endangered species while pondspice is regarded as a threatened or endangered species in some southeastern states.
Florida avocado industry
The state’s avocado crop earns about $30 million wholesale each year, with commercial avocados growing on 7500 acres (30.4 km²) mostly in Miami-Dade County. The avocado crop accounts for more than 60 percent of Florida’s tropical fruit production. 60,000 Florida residents also have at least one avocado tree in their yards. Some estimates project that the disease could cut avocado crop in half, at a total economic impact of about $27 million.Fungicidal efforts
In a September 2008 study, a possible fungicide was tested. The abstract of the study reads as follows:In this study, the systemic fungicide propiconazolePropiconazolePropiconazole is a triazole fungicide, also known as a DMI, or demethylation inhibiting fungicide due to its binding with and inhibiting the 14-alpha demethylase enzyme from demethylating a precursor to ergosterol. Without this demethylation step, the ergosterols are not incorporated into the...
completely inhibited mycelial growth of Raffaelea spp. in vitro at concentrations 0.1 parts per million (ppm) or greater and was fungitoxic at 1 ppm or greater, whereas the fungicide thiabendazole was less inhibitory. None of the ten mature redbay trees that received root-flare injections of propiconazole developed crown wilt symptoms for at least 30 weeks after being inoculated with Raffaelea spp., whereas nine of ten untreated control trees wilted in more than one-third of their crowns. Propiconazole was retained in the stem xylem for at least 7.5 months after injection but was more frequently detected in samples from trees injected 4.5 months earlier and was not well detected in small-diameter branches. Results suggest that propiconazole may be useful in preventing laurel wilt in redbay, but limitations and questions regarding duration of efficacy, rate of uptake, and efficacy under different levels of disease pressure remain.
It is important to note that while this fungicide may be useful in protecting some trees against the wilt, this fungicide is NOT cleared for use on fruit trees that are part of commercial production for human consumption.
Resistance in redbay trees
Some redbay trees may be resistant to the disease, and future research will investigate factors associated with resistance, in the hope that tolerant varieties can be identified and developed.External links
- Center for Invasive Species Research - Laurel Wilt
- Species Profile- Laurel Wilt (Raffaelea lauricola), National Invasive Species Information Center, United States National Agricultural LibraryUnited States National Agricultural LibraryThe United States National Agricultural Library is one of the world's largest agricultural research libraries, and serves as a National Library of the United States and as the library of the United States Department of Agriculture...
. Lists general information and resources for Laurel Wilt. - Don't Move Firewood - Gallery of Pests: Laurel Wilt