J.R.Liberato and R.W. Barreto*

Departamento de Fitopatologia, Universidade Federal de Viçosa, CEP 36570-000, Viçosa, MG, Brazil

*rbarreto@ufv.br

Accepted for publication 28/06/04

Lagerstroemia indica (pride of India, queen’s rose; local name: extremosa) is a small tree in the Lythraceae, native to India, which has become one of the main urban ornamental trees in the southern states of Brazil (Lorenzi et al. 2003). Severe powdery mildew outbreaks have been observed on L. indica trees grown as ornamentals in Viçosa, (State of Minas Gerais, Brazil), beginning in the spring of 2002. The sole fungal disease listed by Mendes et al. (1998) as occurring in Brazil on this host is black mildew caused by Irenopsis lagerstroemiae but Stammer & Tomaz (1991) have also recorded the occurrence of an undetermined species of Oidium on this host. However no description or illustration of this powdery mildew was provided by those authors.

Figure 1: Lagerstroemia indica: flowering individual showing intense colonisation of leaves by Erysiphe australiana.
Note abundant powdery conidial mass and foliar distortion due to fungal attack.

White superficial colonies, with abundant sporulation, developed amphigenously on leaves and also on the non-lignified parts of the stems (Fig. 1). Infected tissues often became distorted and necrotic. Defoliation and death of young shoots often resulted. Hyphae were 2.5-5.0 µm wide, septate, branched, hyaline, smooth, with mycelial appressoria lobed; conidiophores were epiphytic, produced from the external mycelium, unbranched, cylindrical, 37-73 x 6-10 µm, 1-2 septate, hyaline, smooth; foot-cells were cylindrical, straight, 16-32 x 5-10 µm; conidia were produced singly at the apex of the conidiophores, cylindric, doliiform or ellipsoid, 22-44.5 x 11-20 µm l/w ratio 1.4 – 3.2, aseptate, hyaline, smooth (Fig. 2); germ tubes, 1-4 at an end of the spore, were either short and immediately producing multilobed appressoria or moderately long (1–2 x the length of the conidium), ending in a lobed or inconspicuous appressorium (Figs 3 & 4). 

Figure 2 (left): Conidiophore and conidia of Erysiphe australiana. (note typical Pseudoidium configuration of conidial ontogeny), Bar = 30 μm. Figure 3 (middle): Germinating conidium of Erysiphe australiana, with inconspicuous appressorium. Bar = 20 μm. Figure 4 (right): Bipolar germination of conidium of Erysiphe australiana with multilobed appressoria. Bar = 20 μm.

The teleomorph was absent but the anamorph morphology is identical to that described for Erysiphe australiana [syn. Uncinuliella australiana], a common powdery mildew species infecting Lagerstroemia spp. worldwide (Braun, 1987) and reported from Argentina and Venezuela. Representative material was deposited in the herbarium (VIC 26568, VIC 26570). This is the first record of this species of powdery mildew attacking L. indica in Brazil.

Braun U, 1987. A Monograph of the Erysiphales (Powdery Mildews). Beihefte zur Nova Hedvigia 89, 1-700.

Lorenzi H, Souza HM, Torres MAV, Bacher LB, 2003. Árvores Exóticas do Brasil: madeireiras, ornamentais e aromáticas. Nova Odessa, Brazil: Instituto Plantarum.

Mendes MAS, Silva VL, Dianese JC, Ferreira MASV, Santos CEN, Gomes Neto E, Urben AF, Castro C, 1998. Fungos em Plantas no Brasil. Brasília, Brazil: EMBRAPA

Stammer EE, Tomaz R, 1991. Ocorrência de fungos e bactérias fitopatogênicas no Estado do Paraná. Curitiba, Brazil: Centro de Diagnóstico Marcos Enrietti.

The British Society for Plant Pathology