Acremonium cucurbitacearum can cause sudden collapse of melons
In Spain, serious losses have been observed on melons (Cucumis melo) and watermelons (Citrullus lanatus) since the 1980s (see EPPO RS 93/083 and 99/111). Symptoms are characterized by a sudden collapse of the plants, usually as the fruits approach maturity. Affected root systems show a corky appearance, absence of root hairs and small rootlets. The cause of this syndrome has been subject to controversy. In Spain, Acremonium sp. has been consistently isolated from diseased plants and pathogenicity tests have showed that the fungus could induce disease symptoms. However, other researchers have found that Monosporascus cannonballus (EPPO Alert List) was responsible for the disease in many countries. In Spain, it is frequent to find both fungi in diseased plants, with a prevalence of M. cannonballus in certain areas, although Acremonium sp. has been isolated from more than 90 % of the fields studied. It is also noted that an Acremonium species was isolated from roots of diseased melons in USA, in California (from Sacramento valley to upper San Joaquin valley) and Texas (Lower Rio Grande). The Acremonium species occurring in Spain which is pathogenic to cucurbits has been described as a new species called Acremonium cucurbitacearum, and recent studies of molecular characters and vegetative compatibility confirmed the distinctness of this fungi from other Acremonium species. It is thought that Acremonium cucurbitacearum and Monosporascus cannonballus are both pathogenic to cucurbits and induce similar symptoms, but that they may occur under slightly different ecological conditions.
EPPO note: the entry previously concerning Monosporascus cannonballus in the EPPO Alert List will be extended to cover both fungi.
Vicente, M.J.; Cifuentes, D.; Cenis, J.L.; Abad, P. (1999) RAPD-PCR polymorphism and vegetative compatibility group variation in Spanish isolates of Acremonium cucurbitacearum.
Mycological Research, 103(9), 1173-1178.