Etiology and control of the following Wheat diseases: Rust, Tundu disease
Wheat Rust Diseases:-
1. Black Rust (Stem Rust)
2. Brown Rust (Leaf Rust)
3. Yellow Rust (Stripe Rust)
1. Black Rust (Stem Rust):-
Pathogen:- Puccinia graminis tritici
Symptoms:-
> Pustules (containing masses of urediospores) are dark reddish brown - occur on both sides of the leaves, on the stems, and on the spikes.
> Pustules are usually separate and scattered, heavy infections -coalesce.
> Prior to pustule formation, "flecks" may appear. Before the spore masses break through the epidermis, the infection sites feel rough to the touch.
> As the spore masses break through, the surface tissues take on a ragged and torn appearance.
> Survival:- Both survive on stubbles and volunteer crops.
> Alternate host:- Berberis spp.
> Spread:- uredospores from hills.
Management:-
> Mixed cropping and crop rotation.
> Avoid excess nitrogen.
> Sulphur dusting @ 35-40 kg/ha.
> Mancozeb @ 2g/lit.
> Resistant varieties:- Lerma Rojo, Safed Lerma, Sonalika and Chotil.
2. Brown Rust (Leaf Rust):-
Pathogen:- Puccinia recondita
Symptoms:-
> The postules are circular or slightly elliptical, smaller than those of stem rust, usually do not coalesce, and contain masses of orange to orange-brown Urediospores.
> Infection sites primarily are found on the upper surfaces of leaves and leaf sheaths and occasionally on the neck and awns.
> Survival:- Both survive on stubbles and volunteer crops.
> Alternate host:- Thalictrum sp.
> Spread:- uredospores from hills.
Management:-
> Mixed cropping with suitable crops.
> Avoid excess dose of nitrogenous fertilizers.
> Spray Zineb at 2.5 kg/ha or Propioconazole @ 0.1 %.
> Grow resistant varieties like PBW 343, PBW 550, PBW 17.
3. Yellow Rust (Stripe Rust):-
Pathogen:- Puccinia striiformis
Symptoms:-
> The pustules of stripe rust, which, contain yellow to orange-yellow urediospores, usually form narrow stripes on the leaves.
> Pustules also can be found on leaf sheaths, necks, and glumes.
> Survival:- Both survive on stubbles and volunteer crops.
> Alternate host:- unknown.
> Spread:- uredospores from hill.
Management:-
> Mixed cropping and crop rotation.
> Avoid excess “N”.
> Sulphur dusting @ 35-40 kg/ha.
> Mancozeb @ 2g/lit.
> Resistant varieties:- Lerma Rojo, Safed Lerma, Sonalika and Chotil.
Tundu disease of Wheat:-
Pathogen:- Clavibacter (= Corynebacterium) tritici
Symptoms:-
> The early symptoms of tundu disease are wrinkling of lower and twisting of the middle leaves generally evident when the crop is reaching maturity. This is followed by curling and twisting of spikes.
> What happens actually is that a bright yellow sticky slime exudes mainly from the ear and envelops it.
> In addition, the slime trickles down to glumes, stem, and leaf sheaths and envelop them. The slimy substance becomes deeper yellow, hard, and dry in dry weather resulting in retardation of plant growth and distortion of stem and ear.
Management:-
i. As soon as the symptoms appear, the infected plants should be uprooted and burnt.
ii. Seeds not contaminated with nematode galls should be sown preferably in non-infected fields. Seeds can be made gall-free by soaking them in strong solution of common salt (solution called ‘brine’) prepared at the rate of 40 lb. salt dissolved in 25 gallons of water. The galls float on the surface of the solution and are removed. This method is the most effective one and recommended strongly.
iii. In tropical countries, summer ploughing helps destroy bacteria and nematodes occurring in soil by heat and desiccation and thus reduces disease incidence in the next season.