In November 2006, witches' broom symptoms on cacao trees in the Union Vale, La Dauphine, and Robot estates in Saint Lucia, were observed. The disease has since been found in other smallholder plots throughout the island. Estate managers report that up to 50% of the cacao trees are infected. Diseased trees have dense, slightly curved proliferations of shoots with shortened internodes (witches' brooms), arising from the lateral buds. Other symptoms include leaf necrosis, distortion and enlargement of the leaf lamina and veins, and stem swellings. Brooms in cacao are characteristic of infection by M. perniciosa. In May 2007, samples of older, well-dried brooms were sent to the Global Plant Clinic, UK, for confirmation of the pathogen. Aggregations of white saprotrophic hyphae were observed under the bark, which under microscopic examination revealed clamp connections that are characteristic of M. perniciosa. A more definitive morphological identification was obtained by inducing the fungus to produce basidiocarps. The subsequent basidiocarps were pink, tinged with crimson, and had a delicate pileus that was radially grooved with fluted edges. Fungal mycelia isolated directly from the brooms were also tested using molecular characterization. The sequence obtained (GenBank accession no. EU861393) showed greater than 99% homology to 16 strains of this species held in the GenBank database. This is thought to be the first report of witches' broom in cacao from Saint Lucia.
Kelly, P.L.; Reeder, R.; Rhodes, S.; Edwards, N. First confirmed report of witches&#8217; broom caused by Moniliophthora perniciosa on cacao, Theobroma cacao, in Saint Lucia. Plant Pathology (2008) 58 (4) 798-798. [DOI: 10.1111/j.1365-3059.2009.02024.x]