Laurel Wilt in Avocado: Review of an Emerging Disease
- 1. Department of Horticultural Sciences, Indian River Research and Education Center, University of Florida, USA
- 2. Department of Plant Pathology, Tropical Research and Education Center, University of Florida, USA
- 3. Horticultural Research Laboratory, USDA-ARS, USA
Abstract
Laurel wilt, caused by the vascular fungus Raffaelea lauricola, is transmitted by the red bay ambrosia beetle, Xyleborus glabratus, and affects many plants in the family Lauraceae. It was introduced into the United States around 2002 through infested packing material arriving in Georgia. In Florida, the beetle and its associated pathogen have moved progressively throughout the state, arriving in the commercial avocado production area of Miami Dade County in 2011. The fungus grows in galleries and adjacent sapwood of host trees, leading to the disruption of water and nutrient flows. Symptoms include streaks of black discoloration in the sapwood with beetle bore holes on stems and branches of affected trees. Wilt symptoms are associated with the production of gels and tyloses in infected trees. The immediate threat to avocado production in South Florida and the possibility of spread to other states has made identification of control measures a high priority. Current research is testing new fungicides, and different strains of entomopathogenic fungi are showing some efficacy against the red bay ambrosia beetle. However, use of resistant avocado cultivars would likely provide the most sustainable long-term solution. As such, screening of candidate resistant avocado germ plasma by artificial inoculation with the R. lauricola pathogen in the field is under way and protocols to facilitate higher throughput screening are also in development. The goal of these efforts is that promising laurel wilt resistant selections with improved horticultural traits and fruit quality for commercial production will be identified.