Presence and Prevalence ofRaffaelea lauricola, Cause of Laurel Wilt, in Different Species of Ambrosia Beetle in Florida, USA

Abstract

We summarize the information available on ambrosia beetle species that have been associated in Florida with Raffaelea lauricola T.C. Harr., Fraedrich & Aghayeva, the primary symbiont of Xyleborus glabratus Eichhoff and cause of laurel wilt. In total, 14 species in Ambrosiodmus, Euwallacea, Premnobius, Xyleborus, Xyleborinus, and Xylosandrus were either reared from laurel wilt-affected host trees or trapped in laurel wilt-affected stands of the same, and assayed for R. lauricola. In six collections from native species in the southeastern United States [Persea borbonia (L.), Persea palustris (Raf.) Sarg., and Persea humilis Nash] and four from avocado (Persea americana Mill.), extracted mycangia or heads (taxa with mandibular mycangia) or intact bodies (taxa with mycangia in other locations) were surface-disinfested before assays on a semi-selective medium for the isolation of Raffaelea (CSMA+). Raffaelea lauricola was identified based on its characteristic phenotype on CSMA+, and the identity of a random subset of isolates was confirmed with taxon-specific microsatellite markers. The pathogen was recovered from 34% (246 of 726) of the individuals that were associated with the native Persea spp., but only 6% (58 of 931) of those that were associated with avocado. Over all studies, R. lauricola was recovered from 10 of the ambrosia beetle species, but it was most prevalent in Xyleborus congeners. This is the first record of R. lauricola in Ambrosiodmus lecontei Hopkins, Xyleborinus andrewesi (Blandford), and Xyleborus bispinatus Eichhoff. The potential effects of R. lauricola's promiscuity are discussed.

Metagenomic approach of associated fungi with <i>Megaplatypus mutatus</i> (Coleoptera: Platypodinae)

“…On the other hand, Raffaelea species were not detected in this study, although this genus is frequently reported in ambrosia interactions (Ceriani-Nakamurakare et al 2016;Ploetz et al 2017). These results could be due to the known problems of using ITS markers with certain groups of ambrosial fungi (Fraedrich et al 2008;Kostovcik et al 2015).…”

Laurel Wilt in Natural and Agricultural Ecosystems: Understanding the Drivers and Scales of Complex Pathosystems

“…that are native to the southeastern United States, but only 6% (58 of 931) of those that were associated with avocado. Raffaelea lauricola was recovered from 10 of the ambrosia beetle species that were assayed, including X. glabratus, but was most prevalent in Xyleborus congeners [70]. Previous reports had suggested that Raffaelea spp.…”

“…Several other species are associated with redbay, avocado and other lauraceous hosts, but they have been considered as vectors of R. lauricola only recently. The general absence of X. glabratus in avocado orchards that are affected by laurel wilt, the pathogen's presence in other species of ambrosia beetle that are recovered from avocado and other host trees, and the experimental demonstration of pathogen transmission and subsequent laurel wilt development in redbay and avocado suggest that species other than X. glabratus could play roles in the epidemiology of this disease [1,69,70].…”

“…The movement of symbionts amongst ambrosia beetle species had been recognized previously [69,71,73,74]. However, the magnitude and speed with which this has occurred for R. lauricola is unprecedented [70]. Since its introduction into the United States in or before 2002, R. lauricola has been horizontally transferred from X. glabratus to nine additional ambrosia beetle species [1,69,70,75,76].…”

“…were assayed for R. lauricola by Ploetz et al [70]. During 10 experiments, the pathogen was recovered from 34% (246 of 726) of the individuals that were associated with Persea spp.…”