Claviceps purpurea (Fr.:Fr.) Tul. [teleomorph]
Sphacelia segetum Lév. [anamorph]
- Symptoms: At flowering, infected florets produce a yellowish, sticky, sweet exudate (containing conidia) that is visible on the glumes. As the spike matures, kernels of infected florets are replaced by brown to purplish black fungal structures (sclerotia or "ergot bodies") (picture on left). These ergot bodies can reach 20 mm in length (picture on right).
- Development: The primary infection originates from ascospores in fruiting bodies produced by sclerotia from the previous year's crop. Ascospores infect the florets, which then produce the sticky exudate containing conidia. Insects are attracted to the sweet exudate, and carry conidia to healthy florets in the same spike or to adjacent spikes. Rainy or humid weather favors the production of exudate and spores. An ergot body develops in each infected floret; these fungal structures can survive in the soil from one season to the next, and under dry conditions they can remain viable for many years. Sclerotia require cold temperatures before they can germinate.
- Hosts/Distribution: Ergot is found in all small grain cereal crops, especially if sterility occurs for some reason (e.g., frost). Sterile florets tend to open and thus become more liable to infection. The disease is more prevalent in cool, humid climates.
- Importance: Yield losses tend to be small, but losses due to discounted grain quality can be significant and occur worldwide.
