Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Laurel wilt, caused by Raffaelea lauricola, is detected for the first time outside the southeastern United States.

Abstract

In October 2014, a survey for diseases and pests of an emerging fruit crop, avocado (Persea americana), was conducted in Southern Shan State of Myanmar (aka Burma). In the Tuanggyi District (1400 m elevation), monocultures of up to 20 ha were observed, whereas in the Ywangan District (1850 m elevation), avocado trees were used primarily as shade for the production of coffee (Coffea arabica). In both districts, symptoms of laurel wilt were observed on avocado, but no other tree. Trees exhibited sapwood discoloration, leaf necrosis and defoliation, and, according to producers, usually died within a month or two of symptom development. During the survey, isolates with the colony phenotype of Raffaelea lauricola, the cause of laurel wilt, were recovered from symptomatic sapwood on half strength potato dextrose agar amended with streptomycin sulfate. In tests conducted in the USA with DNA from 6 representative isolates from Tuanggyi and Ywangan and PCR primers for 2 diagnostic microsatellite loci, R. lauricola-specific amplicons were generated for each isolate and locus, confirming the identity of the fungus associated with trees exhibiting laurel wilt in Myanmar. Although R. lauricola was previously identified in Asia, and probably introduced from Asia to the southeastern USA with its ambrosia beetle symbiont, Xyleborus glabratus, laurel wilt had previously been reported only in the southeastern USA. This is thought to be the first report of laurel wilt in the Asian native range of R. lauricola and X. glabratus.