It is a common and destructive disease in wheat, It did not cause much concern till very recently it became wild spread. Many of wheat varieties are resistance to rusts. Have been found highly susceptible to the disease. The younger seedlings are not affected. It is only when the crop is 7-8 weeks old that the disease first makes its appearance in the field.
The disease first appears as small, discoloured lesions which are irregularly scattered on the leaves. These spots become the irregular shape and then increase in size and appear brown to grey in colour.
A light yellow zone surrounds the spots. Several lesions coalesce to cover larger areas of the leaf and in several infectious of the whole leaf dies. Black powdery masses of conidia are produced on the surface of the leaves.
The nature of disease resistance and susceptibility in leaf blight of wheat caused by Alternaria triticina. Due to the infection plant will reduce the process of photosynthesis and chlorophyll formation.
The disease is caused by Alternaria triticina, the mycelium of the fungus are deep-seated in the seed embryo of the seed.
Inoculum, in the form of spores either survives in the soil during the absence of hosts is carried on seeds. Seed born inoculum multiples and becomes established in the soil following planting, and it is from here that the pathogen infects the plant once it reaches a susceptible stage.
Leaves become infected either through contact with the ground or rain splash transfers inoculum to the lower leave s. Spores germinate on the surface of the leaves (both upper and lower) producing up to 4germ tubes.
These produce appressoria on the surface and directly infect through the epidermis. Occasionally the infection occurs through the stomata. Hyphae grow through the leaf tissue both intra and extra-cellularly. Hyphae infect cells directly beneath the epidermis and the parenchyma cells. A. triticina produces non-host specific toxics that contributes to cell death and collapse and the development of the lesions.
- Keep traffic out of affected areas and minimize movement of adjacent areas.
- Stop irrigation affected area and use bunding to divert overland flood flows around them.
- Destruction of the infected crop is an effective control.
- Assort plant seeds are free from infection and treated with fungicide before the sowing.
- Collect all plant in the area into bags and destroy or burial, if occur in a small area.
Seed s can be reduced through hot water treatment, pre-soaking seeds in ambient temperature water for 4 hours.
- Use resistance varieties of wheat which are resistance from the leaf blight.
A.triticina can be controlled through the application of fungicides, with a 75% reduction in disease following some fungicides for treatment and effective control with more than one type of fungicide are required for effective control. Fungicides which are effective control mancozeb, ziram, zineb, thiram, propineb and nabam. Propiconazole and tebuconazole are also effective.
The pathogen can also be removed from seeds through a seed-based fungicide application
Combinations of fertilizers, seed treatment, foliar sprays of fungicide, and bio-control agents give effective control of the leaf blight complex caused by A.triticina