EFSA evaluates wheat disease fungus

EFSA has published a scientific opinion on Tilletia indica, a fungus that causes a disease in wheat called Karnal bunt. The Plant Health Panel (PLH) concludes that T. indica can enter the European Union through imported wheat grain. The European Commission asked EFSA for advice on this plant disease following a request from the United States Department of Agriculture (USDA) to review current EU control measures on wheat grain imported from the United States.

The spores of Tilletia indica are very resistant to adverse environmental conditions and can survive in soil for several years. Once established, Karnal bunt disease is very difficult to eradicate. When weather conditions become favourable for the fungus it can infect wheat flowers and then develop spores on kernels. Wheat infected with Tilletia indica has an unpleasant fishy smell and severely infected grain cannot be used for flour.

In support of their request the USDA put forward a mathematical model  which is based on the assumption that a minimum of 150 thousand spores per hectare are needed before the disease can occur in non-contaminated areas. According to this model, the number of spores in wheat grain imported from the US is not high enough to trigger the disease in the EU.

Following its evaluation, the PLH Panel concludes in the opinion that there is no published evidence to show that a minimum number of spores are needed for the fungus to trigger the disease in new areas.  Therefore, EFSA does not consider that the rationale for the proposal put forward by the USDA is scientifically substantiated.

Karnal bunt is currently not present in Europe. All imported wheat grain originating from areas contaminated by the fungus must be tested both at harvest and before shipment and must be found free from the spores of the fungus.

Karnal bunt is widespread in some Asian countries and since the 1970s it has spread to parts of South and North America. In the United States, the disease has been detected in Arizona, California and Texas, areas that export wheat to the EU.

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