Fusarium blight

Fusarium blight of cereals is caused by a complex of fungal pathogens belonging to the genus Fusarium (Kingdom Fungi, Phylum Ascomycota). These are polyphagous pathogens with a wide host range.

The pathogen persists in soil and on crop residues as mycelium, chlamydospores, or sclerotia. Infested seeds and infected soil particles serve as the primary sources of infection.

Fungi of this genus exhibit high ecological adaptability, allowing them to disperse via wind, water splashes, and insect vectors during the flowering stage of cereal crops.

During their growth, these fungi produce harmful secondary metabolites known as mycotoxins (such as deoxynivalenol and zearalenone), which render the grain unsuitable for consumption.

In laboratory settings, identification involves culturing on growth media, where the pathogen typically displays cotton-like mycelial growth, ranging in color from white to pink or purple.

Fusarium species infect almost all cereal crops, including wheat, barley, rye, oats, and maize, causing significant damage to agricultural production worldwide.

The infection leads to a range of diseases, including root rot, seedling blight, leaf spots, and the most severe form, Fusarium head blight (FHB).

Early-stage infection causes mass mortality of seedlings, resulting in poor stand establishment and uneven crop growth across the field.

During the grain-filling stage, the infection results in "white heads," where the grain becomes shriveled, underdeveloped, and covered with characteristic fungal spores.

In addition to direct yield losses, infected grain has reduced germination rates and serves as an inoculum source for subsequent seasons, threatening future harvests.

Disease development begins in early spring when soil temperatures rise above +5…+10°C, triggering the activity of the pathogen within plant residues.

The highest damage occurs during the flowering phase, particularly when weather conditions are wet, warm, and humid, as these factors facilitate spore infection.

Spore dispersal is most active during periods of intermittent rain and wind, allowing the fungus to infect the wheat head via the anthers during the pollination process.

During prolonged wet autumns, the pathogen can also cause snow mold, which develops underneath the snow cover, weakening winter crops significantly.

Dry weather conditions during grain maturation may temporarily suppress further spread, but the mycelium remains viable within the seed, ready to reactivate when moisture returns.

Early symptoms include browning and decay of the roots and the base of the stem, causing plants to wilt and exhibit stunted growth during the vegetative phase.

A classic sign of Fusarium head blight is the emergence of a pink or orange fungal layer on the glumes, which consists of masses of spores and conidia.

Affected sections of the head lose their green color and turn bleached or white, making them easily distinguishable from healthy parts of the plant during field inspections.

Kernels inside infected heads appear chalky, lack their natural luster, and are often covered with white or pinkish fungal mycelium, rendering them light and shriveled.

• Bleached, white-colored heads.
• Pinkish mold growth on spikelets.
• Root and crown rot.
• Shriveled and light-weight grain.
• Premature plant death.

The foundation of management is the use of high-quality, certified seeds treated with effective fungicides to eliminate seed-borne pathogens.

Strict crop rotation is essential, as planting cereals after cereals or maize increases the inoculum density in the soil and promotes disease outbreaks.

Cultural practices such as thorough plowing and burial of crop residues help accelerate the decomposition of plant material and reduce the survival of the fungus.

Fungicide applications during the flowering stage are the most effective way to prevent head infection and minimize mycotoxin contamination in the final grain harvest.

Balanced mineral nutrition, specifically appropriate potassium fertilization, helps improve the plant's immune system and resistance to various fungal diseases.