Heads of infected plants usually emerge from the boot slightly earlier than normal. Prior to heading infected plants may have dark green, erect leaves, sometimes with chlorotic streaks. Disease Cycle Wheat plants are infected only during flowering by wind blown spores from nearby smutted heads. Rain and insects may also disseminate the spores. Dispersal of spores at flowering is critical to the perpetuation of loose smut because infection usually takes place during the two days after flowering.
Plants become resistant to infection one week after flowering.
Once the spores have been deposited in open flowers, they soon germinate and the mycelium grows through the ovary wall into the embryo of the developing seed. 60 to 71 degrees F favor infection. After establishing in the embryo of the kernel, the mycelium of the fungus becomes dormant. Infected kernels do not appear different from healthy ones. When infected kernels are planted and germinate, the fungus becomes active again.