Wheat and barley blight in Iran was first reported by Esfandiari in 1326.
This disease exists in all regions of Iran and its damage is of secondary importance compared to latent wheat blight.
Symptoms:
Before clustering, there is no discernible difference between diseased and healthy clusters. The diseased plants soon cluster and the whole cluster turns into a black mass. The black mass is actually the fungal teliospores. The teliospores are a spherical cell with a thick wall and appear light brown under a microscope. The formation is spread by wind and insects on the field surface and only the main axis remains from the infected axis. The spread of teliospores is often healthy clusters when the inflorescence appears.
cause of disease:
Ustilago nuda is the causative agent of obvious black spot disease in wheat and barley. Teliospores of this fungus are 6.5 to 7 microns in diameter and germinate easily under favorable conditions and form basidiomycetes.
biology:
The fungus overwinters as dicotyledonous mycelium in wheat and barley grains. After sowing the seeds and simultaneously with the activation of its seedlings, the fungal mycelium enters the seedling and then goes to its end growth point. The terminal bud moves parallel to the plant growth through the intercellular space and reaches the cluster formation site. During the formation of the fungus cluster, it attacks all the young spikes and infects them. Fungi quickly turn into millions of teliospores or black seeds in their seeds. The spore mass is first covered as a thin membrane and then released by bursting the membrane when the inflorescences of healthy plants are being pollinated and are transferred to the inflorescence by wind or insects.
Control:
Fighting the apparent black spot disease of wheat and barley was difficult in the past due to the presence of fungal filaments in the seeds and the absence of systemic fungicides. At that time, contaminated seeds were disinfected with hot water. Nowadays, systemic fungicides are used as seed disinfectants. The systemic toxins used can be used as Toboconazole 2% Ds) at a rate of 1.5 kg per thousand kg Seed – Tabuconazole (70% Wp) at 150 g / 100 kg Seed – Carbendazim 60% Wp)) At a rate of two kilograms per thousand liters of water can be used to disinfect seeds
