The diagram below summarizes the management levers that can be used in organic farming. To learn more about a particular management lever, click on the respective box within the scheme (or scroll down):

Favour a quick emergence

The fungus causing common bunt is able to penetrate a wheat seedling in a well-defined time window between germination and the 3-leaf stage (see section: "what is common bunt?"). It will then thrive and grow within plant tissues. Fostering rapid emergence and development of seedlings therefore reduces the potential for the fungus to infect plants and spread. Sowing under conditions as favourable as possible to germination and emergence of the crop reduces the risk of infection with common bunt.

However, it is not easy to predict exactly what will promote rapid emergence from place to another place and year one year to the next. Some farmers practice early and/or shallow sowing.

Return to top

Crop rotation

A diversified rotation is a basic principle for the prevention of plant diseases in organic agriculture. The closer the susceptible cereal crops follow each other in the rotation, the higher the risk of common bunt.

Return to top

Soil cultivation

Bunt spores need oxygen and water to germinate. Compacted soils therefore hinder their germination.

When the soil of a plot is contaminated, deep tillage in the first year of infection buries the spores, making it difficult for seedlings to become infected the following year. However, another deep ploughing will bring the spores back to the surface. Also, buried spores, which do not find the oxygen necessary for germination, are preserved. The inoculum present in the soil therefore does not degrade.
On the other hand, the vast majority of spores remaining on the surface germinate within 2 to 4 months following the harvesting a bunted wheat, provided the soil is sufficiently moist. Also, colembols living in the first few centimetres of soil can ingest and destroy spores (Borgen, 2001). In order to promote spore degradation as much as possible, it may then be preferable to delay ploughing and only till in winter or spring after the harvest to plant a spring crop.

In tillage systems, it is recommended to wait five ploughings before growing another susceptible cereal crop on an infected plot. Spore biology and survival in no-till systems has not yet been studied sufficiently. We therefore advise to wait 5 years in no-till systems.

Return to top

Observing the crop

Regular observation of the crop allows early detection of bunt in order to take measures to limit damage, for example by eliminating plants presenting symptoms (in small fields). The symptoms visible in the field are described in the "symptoms and detection" section. Observation is particularly important in the case of seed production.

Return to top

Harvest infected fields after healthy ones

If you do decide to harvest an infected cereal crop, harvest plots where bunt symptoms have been observed after the healthy plots, to avoid any cross-contamination. Remember to clean harvesting equipment by harvesting a resistant crop before going into another susceptible crop or sharing it with your neighbor!

Return to top

Cleaning harvesting equipment

Bunt spores can be transmitted by harvesting equipment. A Danish study (Kristensen & Borgen, 2001) concluded that after harvesting a contaminated field, a combine harvester must be filled and emptied 4 times with healthy seed to achieve an acceptable contamination rate. When a harvester has been used for a crop with bunt, or when the last harvested field (shared equipment, contractor) is unknown, it is best to first harvest crops for grain production, and fields for seed production at the end.

Care must also be taken to ensure that any other equipment used during harvesting and for post-harvest is clean: silos, big-bags, cleaning equipment, etc.

Return to top

Destroying the harvest

When bunt-infected wheat is harvested, the smell of rotten fish can make the batch unfit for consumption, and it is then rejected by the mill and for animal feed. Destroying it avoids preserving or even spreading a source of inoculum on the farm.
When significant contamination is observed in the field, field destruction is sometimes preferable in order to avoid the spread of spores by threshing: despite the disturbance to soil biology, burning (which may require an authorization in your region or country) can then be considered (preceded by mowing if it causes a limited dispersion of dust and therefore limited dissemination of spores). The crop can also be destroyed and left on the field, e.g. by using a stubble cultivator. In any case, the plot must be considered as infected.

Return to top

At least 5 years before growing another susceptible cereal

When bunt has occurred in a plot, the soil can be considered as being infected. The survival of spores in the soil is highly dependent on soil conditions. Survival of more than 10 years has been observed in experimental conditions (Johnson, 1990), but generally it is sufficient to wait 5 years to reseed a cereal that is susceptible in the respective field (see "Soil cultivation" above for detail).

Return to top