Further data on Claviceps africana (sorghum ergot)
As reported previously in EPPO RS 97/031, 97/073 and 97/119, sorghum ergot (also called sugary disease) caused by Claviceps africana is spreading in the Americas and Australia. Three species of Claviceps infecting sorghum have been described (their anamorph being in all cases Sphacelia sorghi): Claviceps sorghi, C. africana and an unnamed Claviceps sp. found on sorghum in Japan. Ergot of sorghum caused by C. sorghi was first observed in India in 1915, it occurs also in Myanmar, and the Philippines. In Africa, sorghum ergot was first observed in Kenya in 1924 and is now widespread in eastern, western and southern Africa. In 1991 with the first description of the teleomorph, the pathogen found in Africa was recognized as a separate species: C. africana. Recently, C. africana has been spreading very rapidly in the Americas, and in Australia, in countries where sorghum (Sorghum bicolor) is an important crop. The distribution list below gives details of its spread. C. africana attacks sorghum (Sorghum bicolor); but other Sorghum species (e.g. the weed S. halepense) and pearl millet (Pennisetum glaucum) can host the disease. Ergot attacks unfertilized ovaries and the two major symptoms are the presence of honeydew oozing from infected florets, and of fungal sphacelia or sclerotia between the glumes of infected florets. The disease is particularly damaging for the production of F1 hybrid seeds. The development of the disease is favoured by cool (approximately 19 °C), wet, cloudy weather during floret opening and from the onset of anthesis to fertilization. Its spread can be extremely rapid, as for example in Brazil, one month after the discovery of the first focus, it was found on 800,000 km². The disease cycle is quite complex but it is thought that the main means of dissemination is wind dispersal of secondary conidia. Secondary conidia are also produced on honeydew that drips and falls onto wet soils. They can also be dispersed during farming and postharvest operation. Sclerotia are present in infected seed lots and can also spread the disease. To control C. africana, cultural methods (appropriate dates of sowing, elimination of infected panicules, rotation, etc.), fungicide treatments (crop sprays with benomyl, propiconazole, seed treatment with thiram or captan) and seed processing (washing and drying to remove sclerotia) can be used. Further breeding research is needed to find sources of resistance to the disease.
Distribution List: Claviceps africana
EPPO region: absent.
Asia: Japan, Thailand, Yemen#.
Africa: Angola#, Botswana, Burundi#, Ethiopia, Ghana#, Kenya#, Lesotho#, Malawi#, Mozambique#, Nigeria, Rwanda, Senegal#, South Africa, Swaziland, Tanzania#, Uganda#, Zambia, Zimbabwe.
North America: Mexico (first in Tamaulipas in 1997 – later in Guanajuato, Jalisco, Michoacan), USA (first in Texas in October 1997 and later in Kansas*, Georgia*, Nebraska*; it may be present in Mississippi (Zummo et al., 1998)).
Central America and Caribbean: Dominican Republic (1997), Honduras (end of 1996), Haiti*(1997), Jamaica (1997), Puerto Rico (1997).
South America: Argentina (mid-1996), Bolivia (mid-1996), Brazil (1995 - Goias, Minas Gerais, Sao Paulo), Colombia (end of 1996), Uruguay (mid-1996), Paraguay* (mid-1996), Venezuela (end of 1996).
Oceania: Australia (1996 in Queensland, then in New South Wales).
* new records corresponding to recent introductions.
# new records according to the EPPO Secretariat, but the disease has been reported in these countries at least 10 years ago.
Sources
Bandyopadhyay, R.; Frederickson, D.E.; McLaren, N.W.; Odvody, G.N.; Ryley, M.J. (1998) Ergot: a new disease threat to sorghum in the Americas and Australia.
Plant Disease, 82(4), 356-367.
Isakeit, T.; Odvody, G.N.; Shelby, R.A. (1998) First report of Sorghum ergot caused by Claviceps africana in the United States
Plant Disease, 82(5), p 592.
Velasquez-Valle, R.; Narro-Sanchez, J.; Mora-Nolasco, R.; Odvody, G.N. (1998) Spread of ergot of Sorghum (Claviceps africana) in Central Mexico.
Plant Disease, 82(4), p 447.
Zummo, N.; Gourley, L.M.; Trevathan, L.E.; Gonzalez, M.S;; Dahlberg, J. (1998) Occurrence of ergot (sugary disease) incited by a Sphacelia sp. on Sorghum in Mississippi in 1997.
Plant Disease, 82(5), p 590.
Further reading and pictures on INTERNET
http://www.cgiar.org/icrisat/
http://www.ars-grin.gov/ars/SoAtlantic/Mayaguez/sorghumnews.html
http://www.pioneer.com/xweb/usa/txt/pio/company/high/sorgh.html