First Report of Gulf Licaria, Licaria trianda, as a Suscept of Laurel Wilt

Gulf licaria, Licaria trianda (Sw.) Kosterm., is a federally endangered member of the Lauraceae plant family in Miami-Dade County, Florida. It was never common in the area, and urban development has extirpated it from most of its former range; as of 2001, fewer than 10 trees remained in a single, remnant habitat in the continental United States, Simpson Park (25°45′31″N, 80°11′46″W) (2). Laurel wilt, caused by the fungus Raffaelea lauricola T. C. Harr., Fraedrich & Aghayeva, has recently devastated members of the Lauraceae in the southeastern United States, most notably redbay, Persea borbonia (1). As R. lauricola and its vector, the redbay ambrosia beetle Xyleborus glabratus, have spread in the region, an increasing number of taxa in this plant family have been affected by this disease (1). In 2012, seedlings of gulf licaria and redbay were obtained from local nurseries; they were grown in 30 liter pots, 1.3 m tall, had stems 3 cm in diameter 20 cm above the soil line, and were maintained with standard watering and fertilization practices. In two pathogenicity experiments on July 6 and September 25, 2012, three plants each of gulf licaria and redbay were inoculated with an isolate of R. lauricola, RL4, as described in previous experiments (3), and two plants each were mock inoculated (water control). RL4 is deposited as CBS 127349 at the Centraalbureau voor Schimmelcultures (CBS Fungal Biodiversity Centre, Utrecht, The Netherlands), and a SSU rDNA sequence for it is deposited in GenBank under Accession No. HM446155. Beginning 2 weeks after inoculation, plants were rated on a weekly basis for the development of external symptoms, on a subjective 1 (no symptoms) to 10 (dead) scale (3). After 5 weeks, inoculated plants of redbay in each experiment (positive control) had died after first developing symptoms of wilt and necrotic foliage that are typical for this disease (1). In contrast, inoculated plants of gulf licaria developed severe symptoms by the time experiments were terminated 6 and 11 weeks after inoculation; chlorosis developed on some of the leaves of all plants and these eventually abscised (mean external severities of 7.3 and 6.5, respectively), but plants did not die. Brown to greyish discoloration of sapwood developed in all inoculated plants, and the pathogen was recovered from symptomatic sapwood on CSMA (3). No symptoms developed on mock inoculated plants and the pathogen was not recovered from them. It is concluded that gulf licaria is susceptible to laurel wilt, but that it is apparently less susceptible than redbay. Whether X. glabratus is attracted to, or will bore into, gulf licaria is not known, but will play a significant role in the extent to which this rare tree is affected by laurel wilt. References: (1) S. W. Fraedrich et al. Plant Dis. 92:215, 2008. (2) G. D. Gann et al. Rare Plants of South Florida: Their History, Conservation, and Restoration. Institute for Regional Conservation, Miami, 2002. (3) R. C. Ploetz et al. Plant Pathol. 61:801, 2012.