First report of Pestalotiopsis macrochaeta on Carapa guianensis

Carapa guianensis (Meliaceae) is a tree which occurs naturally in Central and South America, but which is also planted as ornamental. It has attracted much attention because its seeds contain an oil with medicinal properties. The common name of C. guianensis in Brazil is andiroba, hence andiroba oil, while in Guyana it is known a karaba and crabwood oil.

In 2003 a foliar blight was observed in the lower canopy of trees in the state of Roraima, Brazil (Fig. 1). Closer examination revealed punctiform acervuli (Fig. 2), which contained conidia typical of Pestalotiopsis (Nag Raj, 1993). These were smooth, long-fusiform, 4-septate, with three intermediate cells almost concolorous and 2 to 3 apical appendages. They measured 24-34 x 5-8 µm, with median cells 16-21 µm, apical appendage 16-34 µm long and a single basal appendage 5-8 µm long. Mycelial growth on potato dextrose agar media was cottony white and conidia were produced in ink-like fruiting bodies (Fig. 3). Based on these observations the fungus was identified as Pestalotiopsis macrochaeta (Zhang et al., 2003).

To demonstrate pathogenicity, a suspension of 10⁶ conidia per ml in distilled water was sprayed on five, 8-month-old plants and distilled water only on another five (as controls). The plants were kept in a humid chamber for 24 hours. After seven days a blight similar to that observed in natural infections was seen only on the inoculated plants (Fig. 4). P. macrochaeta was reisolated from these plants. Up to 50% of the leaves of inoculated plants were blighted.

Despite searches, no published information on diseases of C. guianensi could be found, despite its widespread distribution in Central America, the Caribbean region and the northern part of South America. Although the foliar blight does not appear to be a serious disease at present we draw attention to this first report of P. macrochaeta on C. guianensis because of increased interest in harvesting the oil from the tree. As more plantations are established the importance of pests and diseases is likely to increase.