Symptoms usually first appear during or shortly after flowering. A few or all of the spikelets on the spike may be bleached. If the rachis is infected, the spike above the point of infection will bleach out. Frequently, the entire head is bleached and devoid of grain. Later, tiny fruiting bodies resembling pepper grains will appear on the surface of the grain.
Infected grain is underweight and shriveled.
Infected seed either fail to germinate or produce weakened seedlings that usually die soon after they emerge from the soil. Persistence And Spread. Fusarium species that cause wheat scab or head blight survive and reproduce on volunteer wheat, grass hosts, or on plant debris and other organic matter in the soil. Spores are blown from Fusaria living on plant debris in the soil and other weed host plants to wheat spikelets. Under warm, moist conditions spores land on spikelets, germinate, and invade glumes, floral parts, and other susceptible plant parts.