Diseases of wheat:
this article you will learn about various diseases of wheat while cultivation of wheat in your field and for optimum yield performence you have know all the symptomes and recommended management practices.
List of diseases of wheat:
1)Black or stem rust:
casual organism: Puccinia graminis tritici
The first symptom of rust infection is flecking of leaves, leaf sheaths, culms and floral structures. These flecks soon develop as oblong, reddish brown uredo-pustules, frequently merging into one another, finally bursting to expose a mass of brown uredospores. When large number of uredosori burst and release their spores, the entire leaf blade and other affected parts will have a brownish appearance even from a distance. Later in the season, teleutosori are produced. They are conspicuous, linear or oblong, dark brown to black, and often merging with one another, to cause linear patches of black lesions, which account for the name black rust. On maturity the teleutosori burst open, exposing masses of dark brown teleutospores. In the transitional stage, there is a mosaic of brown and black masses of spores on the affected tissues, which dry up prematurely. Moreover, in the case of severe infections the diseased plants are stunted and produce small spikes and shrivelled grains, or no grain at all.
- Eradication of self sown wheat plants and weed hosts.
- Adjust time of sowing.
- row resistant varieties like Kalyanasona, Sonalika, Choti Lerma, Lerma Rojo, Safed lerma, NP 700 & 800.
- Avoid late sowing
- Balanced application of nitrogenous fertilizers
- Seed dressing with [email protected]% followed by two sprays with the same chemical.
- Spray twice or thrice with [email protected]% or [email protected]% or [email protected]% , at 15 days interval.
2)Leaf-brown or orange rust
casual organism: Puccinia recondita
The first symptom of the disease is the appearance of minute, round, orange sori, irregularly distributed on the leaves, rarely on the leaf sheath and stem. The sori turn brown with maturity. As the disease advances, the telial stage may be found in the same pustule. The telia are small, oval to linear, black and covered by the epidermis. The telia are also found on the leaf sheath. Severe rusting of leaves causes reduction in yield.
- Grow resistant varieties like Sonalika, NP 700 & 800, Lerma Rojo and Safed Lerma.
- RH-124, an Indofil product is very specific to brown rust (or) spray dithiocarbamates like [email protected]% or [email protected]%.
- Seed dressing with [email protected]% followed by two sprays with the same chemica.
2)Yellow or stripe rust:
casual organism: Puccinia striformis
The uredosori appear as bright yellow pustules chiefly on the leaves. But in severe infections they may be seen on leaf sheaths also. The sori are elongated and are arranged in linear rows between the veins of the leaf and hence it is referred as stripe rust. The sori are mostly sub-epidermal and are remained covered by the epidermal layer and break only at the time of crop maturity. The teleutosori appear late in the season and are also arranged in linear rows. They are compact, elongated, and black which remain subepidermal. They do not break through epidermis for a long time remaining as black crust.
- Grow resistant varieties like Lerma Rojo, Safed Lerma, Sonalika and Choti Lerm.
- Spray [email protected]
- Removal and destruction of weed hosts.
causal organism: Ustilago nuda tritici
The symptoms are evident only at the time of emergence of the panicle from boot leaf. All the spikelets in a panicle transform into a mass of black powdery spores. The infected panicle emerges two days earlier than healthy and the spores are covered with the silvery membrane. This thin membrane gets ruptured exposing the mass of black spores. The spores are easily blown by wind leaving the bare rachis.
- Grow resistant varieties kalyanasona, PV 18, WG 307 and HD 450.
- Hot water treatment (Jensen, 1908): Soak the seed in cold water for 4 hours and then immerse the seed in hot water at a temperature of 132 0F or 520C for about 10 minutes. Dry the seed in shade before sowing.
- Solar seed treatment (Luthra and Sattar, 1934): Soak the seed in water for 4 hours (8 AM to 12 Noon) and expose the seed to the hot sun for 4 to 5 hours (from 12 Noon to 5 PM) on cement or rocky surface. This can be practiced in the areas where the summer temperatures are high (42-440C) .
- Anaerobic seed treatment (USA): Soak the seeds for 2-4 hours in water between 60700F and keep the moist seeds in air tight containers for 65-70 hours and there after dry the seed.
- Seed treatment with systemic chemicals like [email protected]% or [email protected]
4) Karnal bunt:
causal organism: Neovossia indica
The infection is usually confined to a few grains in the spike with irregular arrangement. In some cases the infection may spread to only a part of the grains. In severe cases, the grain is reduced to black shiny sac of teliospores. As the grains mature the outer glumes spread and the inner glumes expand, exposing the bunted grains. The bunt balls are first enclosed by the pericarp but when it bursts the masses of bunt spores are exposed. The bunt affected plants emits a foul smell which is mainly due to the presence of Trimethyl amine.
- Grow tolerant varieties: WL 1562, HD 2281, etc. Use resistant sources like wild species of Aegilops and Triticum, HD 2329, HD 29 and HD 20 for breeding programme.
- Follow strict quarantine measures.
- Use disease free seed for sowing.
- Judicious application of nitrogenous fertilizers.
- Adjust date of sowing.
- Intercropping with Gram or Lentil crops.
- Seed treatment with copper carbonate or [email protected]/kg seed.
- Spray with [email protected]% or [email protected]% or [email protected]% or bitertanol.
5) Leaf blight:
casual organism: Alternaria triticina
Reddish brown oval spots appear on young seedlings with bright yellow margin. In severe cases, several spots coalesce to cause drying of leaves. The young leaves are not usually infected. Heavily infected fields display a burnt appearance even from a distance. In some varieties reduction in grain yield is as high as 90% if the infection takes place at or before the boot leaf stage.
- Soak the seeds in water for 4 hrs followed by 10 min. dip in hot water at 520C.
- Grow resistant varieties like Co.25, Sonalika, Arnautka, E6160 and K7340.
- Spray the crop with [email protected]% or [email protected]%
6)Tundu disease or yellow slime disease of wheat:
casual organism: Anguina tritici (Nematode) + Corynebacterium tritici or Clavibacter tritici
The tundu disease is characterized by the twisting of the stem, distortion of the ear head and rotting of the spikelets with a profuse oozing of yellow liquid from the affected tissues. The ooze contains masses of bacterial cells. The nematode alone causes winkling, twisting and various other distortion of the leaves, stem and produce small round galls on the leaves. The infected plants are shorter and thicker than healthy plants. In the distorted earheads dark galls are found in place of kernels. When the bacterium is associated with the nematode, the disease symptoms are intensified at the flowering stage and yellow ear rot sets in due to combined action of the nematode and bacterium. The earhead becomes chaffy and the kernels are replaced by dark nematode galls which also contain the bacterium. The infected plants produce more tillers than the healthy ones. Another interesting feature is the early emergence of ears in the nematode infected plants which is about 30 to 40 days earlier than the healthy ones.
- Sow gall free seeds. Separate the galls from the seed by floating in brine at 160 g of sodium chloride in liter of water.
- Wheat, barley or oat should not be sown in the infested soil.
- Spray the crop with streptocycline, 1g in 10 liters of water.