Claviceps purpurea - Ergot

Claviceps purpurea - Ergot of Rye

Taxonomy

Phylum: Ascomycota

Class: Sordariomycetes

Order: Hypocreales

Family: Clavicipitaceae

The name Ergot is applied to a group of similar tiny ascomycetes fungi that occur on grasses (including in the past some cereal crops). Their lifecycles are complex. The sclerotia develop in place of the seeds once spores of a Claviceps fungus have infected grass flowers. Ryegrass is particularly susceptible because of its open flower form. The Ergot mycelium then destroys the flower ovary and ultimately produces vast numbers of conidia (asexual spores) that can infect grass florets.

Visible eventually as blackened sclerotia in the husks of the florets, they contain toxic alkaloids. When eaten with grain these sclerotia are the cause of the illness known as ergotism, with such notorious symptoms as St Anthony’s Fire. (The name is a reference to The Brothers of St. Anthony, who developed treatments for victims of this ailment, and to the burning sensation in limbs resulting from eating Ergot-infected cereals.)

Identification Guide

Description

The sclerotia (pictured above on a foxtail grass nflowerhead) are banana-shaped; purple, becoming black; 1 to 2mm dia., and 1 to 1.5cm long; falling to ground in winter, at which point the sexual stage of the lifecycle begins.

Spores

Creamy-white.

Habitat

On untreated cereal crops and on grass seedheads. Rye and ryegrasses are particularly susceptible to this fungal infection.

Season

April to September.

Occurrence

Frequent.

Similar species

The common name Ergot refers to many similar ascomycetes fungi of the family Clavicipitaceae.