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Disease Management of Fusarium head blight

Resistant cultivars of wheat and barley

A large body of research has focused on the use of resistant cereal cultivars for the control of Fusarium head blight. Thousands of plant lines are subjected to artificial inoculation with F. graminearum (Figure 18). Those lines harboring reduced fungal growth and low levels of contamination with the mycotoxin DON are further selected for additional breeding efforts. To date, there does not appear to be a high-yielding wheat or barley cultivar that is completely resistant to F. graminearum. However, in recent years significant progress has been made in developing partially resistant cultivars in many of the bread wheats. In contrast, barley breeding programs have not seen such progress. The lack of resistant barley cultvars is due to the zero tolerance of Fusarium infected barley seed in the malting/brewing industries.

Figure 18

Agronomic considerations

Crop sequence (what crops were planted, and when) and tillage (soil incorporation of crop residues) have been shown to affect the incidence of FHB. In recent years, decreases in tillage are thought to have contributed to regional scab epidemics by increasing levels of inoculum available for infection.

Since the risk of FHB depends on a viable inoculum source, the management of cereal debris on the soil surface may or may not impact the level of FHB. The relative contribution of inoculum from local and distant sources is not yet fully understood. In regions where there is a significant source of airborne inoculum, local management of the disease (on a single farm) may not be effective.

Fungicides

Chemical controls, such as fungicides, provide partial control of FHB and associated mycotoxin contamination. A number of foliar fungicides have been used to manage FHB in some areas and are applied around the period of wheat flowering. In many areas, fungicides are rarely used for FHB control because of high cost, variable efficacy, and the erratic nature of FHB epidemics. Research continues to identify fungicides that are more effective for the control of FHB.

Many commercial fungicides that are routinely used for cereal seed treatment also reduce the risk of Fusarium seedling blight.

Biological Control

Several investigators are focused on finding affordable and environmentally compatible biocontrol agents for the management of FHB. Certain strains of spore- producing bacteria (such as Bacillus subtilis) and yeasts show some promise for the control of FHB and the reduction of mycotoxin contamination (Figure 19).

Figure 19

Integrated management

Integrated management of FHB may one day be achieved by the combined application of biocontrol agents and fungicides to flowering wheat and barley varieties with partial resistance. Disease forecasting models may help to optimize FHB management by targeting fungicide and biocontrol applications.