Fungi associated with Eichhornia crassipes (water hyacinth) in the upper Amazon basin and prospects for their use in biological control.

Surveys were undertaken in 1998 and 1999 in the upper Amazon basin of Ecuador and Peru to collect and catalogue the mycobiota associated with water hyacinth in the river and lake systems. The results indicate that three groups of fungi, which occupy distinct niches on the plant, can be delimited: biotrophic fungi, colonising green leaf tissue, often without significant visible symptoms (e.g. Didymella and Mycosphaerella); necrotrophic fungi, causing prominent leaf lesions (e.g. Leptosphaeria, Colletotrichum, Myrothecium, Phaeoseptoria and Stagonospora); and fungi associated with and isolated from petioles previously invaded by coevolved insect natural enemies, such as Taosa and Thrypticus spp. (e.g. Acremonium, Cephalosporiospsis, Cylindrocarpon, Cylindrocladium and Stauronema). Some of these represent new host records, as well as undescribed taxa. A re-analysis of the mycobiota associated with water hyacinth worldwide reveals that most of the records originate from the USA and the Palaeotropics, where the plant is a major invasive species, and where, as a consequence, most research on its control has been concentrated. Fungal genera such as Alternaria and Cercospora, which traditionally have been favoured as biocontrol agents, seem to be absent or rare on E. crassipes in the Upper Amazon.