Application of Propiconazole in Management of Laurel Wilt Disease in Avocado (Persea americana Mill.) Trees

Laurel wilt is a vascular disease of Lauraceous plants caused by a fungus (Raffaelea spp.) that is carried by a recently introduced, nonnative ambrosia beetle (Xyleborus glabratus). The disease is devastating to Persea species including redbay (Persea borbonia) and avocado (Persea americana) trees in forests, parks, orchards and residential areas in the southeastern United States. Avocado is the most important agricultural crop susceptible to laurel wilt. Management strategies for reducing its impact in Persea sp. (specifically P. americana) are needed. The USDA ARS NPGS collection of avocado is conserved at the National Germplasm Repository (NGR) in Miami-Dade County Florida. Although the avocado collection is currently free from the ambrosia beetle and the laurel wilt disease, it is believed to be only a matter of time before this insect/disease complex reaches the collection. Macro infusion of the fungicide Propiconazole (Alamo (R)) has been shown to control the disease in red bay and other oak species. In this study, the use of the systemic fungicide Propiconazole (Alamo (R)) macro infusion through the root system was infused at the recommended doses. Plants were infused in June 2009 and again in February 2011. The rate of application varied greatly with the diameter of tree trunk at breast level (dbl). The rates recommended on the Alamo (R) label were the rates use initially. Results from research conducted in redbay suggest propiconazole could be useful in preventing laurel wilt in redbay and other Persea species. Preliminary results demonstrated propiconazole was present in branches of trees injected 14 months after treatment.