Recovery Plan for Laurel Wilt of Avocado

Authors: PLOETZ, RANDY - University Of Florida; HARRINGTON, TOM - Iowa State University; HULCR, JIRI - North Carolina State University; BOSTOCK, RICHARD - University Of California; ESKALEN, AKIF - University Of California; FABER, BEN - University Of California; CRANE, JONATHAN - University Of Florida; HARMON, CARRIE - University Of Florida; INCH, SHARON - University Of Florida; PALMATEER, AARON - University Of Florida; PENA, JORGE - University Of Florida; SMITH, JASON - University Of Florida; Kendra, Paul; Schnell Ii, Raymond; FRAEDRICH, STEPHEN - Us Forest Service (FS); HANULA, JIM - Us Forest Service (FS); MAYFIELD, BUD - Us Forest Service (FS); RABAGLIA, BOB - Us Forest Service (FS); WINGFIELD, MIKE - University Of Pretoria

Submitted to: Office of Pest Management National Plant Disease Recovery System
Publication Type: Government Publication
Publication Acceptance Date: 7/21/2011
Publication Date: 8/1/2011
Citation: Ploetz, R., Harrington, T., Hulcr, J., Bostock, R., Eskalen, A., Faber, B., Crane, J., Harmon, C., Inch, S., Palmateer, A., Pena, J., Smith, J., Kendra, P.E., Schnell Ii, R.J., Fraedrich, S., Hanula, J., Mayfield, B., Rabaglia, B., Wingfield, M. 2011. Recovery Plan for Laurel Wilt of Avocado. Office of Pest Management National Plant Disease Recovery System. 3.

Interpretive Summary: n

Technical Abstract: Laurel wilt kills American members of the Lauraceae plant family, including avocado (Persea americana). The disease threatens commercial avocado production in Florida, as well as the National Germplasm Repository for avocado in Miami (USDA-ARS). Elsewhere in the US, major (California) and minor commerce in the fruit (Texas, Hawaii and Puerto Rico) could be impacted if the disease continues to spread. Laurel wilt is caused by a recently described fungus, Raffaelea lauricola, which has an Asian ambrosia beetle, Xyleborus glabratus, as a vector both in Asia and the USA. X. glabratus originated in Asia and was reported for the first time in the Western Hemisphere in May 2002 in Port Wentworth, GA, a maritime port near Savannah. Shortly afterwards, laurel wilt was observed in the vicinity on redbay, Persea borbonia, a dominant component of Coastal Plain forest communities in the southeastern USA. Redbay has been devastated in the ensuing epidemic, and a separate recovery plan for it and other native forest suscepts has been written. The first avocado trees were killed by laurel wilt in 2006 in Duval County, FL, and the disease has been documented on avocado as far south as Brevard County, FL. Virtually all commercial avocado production in Florida is centered in Miami-Dade County, ca 200 km south of Brevard County. In February 2011, laurel wilt was confirmed on swampbay, P. palustris, in Miami-Dade County, about 3 km north of the nearest commercial avocado production area. In general, American members of the Lauraceae are more susceptible to the disease than are those from the beetle’s Asian home range. Host and X. glabratus interactions are less clear. Scant information is available on the extent to which lauraceous and non-lauraceous taxa serve as hosts and reservoirs for the vector and pathogen. Laurel wilt has spread due to its mobile insect vector, the movement of infested wood, and the presence of native and non-native plants throughout the southeastern USA that are susceptible to the disease and on which the vector reproduces. Rapid spread has occurred where there are high population densities of redbay and swampbay (some taxonomists do not distinguish these species). In avocado, movement of the pathogen by root grafts is probable and by pruning equipment is possible; the possibilities of movement via fruit, seed or scion material are under investigation. Diverse disease management strategies have been examined for avocado, including host resistance and the use of fungicides and insecticides. To date, no highly efficacious and cost-effective measure has been identified. In the absence of such a measure, holistic considerations of host tolerance, chemical mitigation and cultural measures will be needed. In the latter situation, the prompt identification and removal of infected trees (sanitation) before emergence of brood will probably play a significant role; sanitation will rely on rapid and specific means by which laurel wilt could be diagnosed.