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Rust causes yellowishness in wheat. Checking Methods and management strategies

What is Rust Disease?

Rust is a  fungal disease that mostly develops in winter crops in a cool climate. This is caused by pathogen fungi which are parasites that infect living plants. The fungus starts this process by spore formation on the plant surface. Rust transfer from infected to healthy plant by spore formation

This disease is causing a reduction of 15 Million tons of Wheat every year in the world. Rust can cause 30% Yield Losses. There are three distinct diseases occur on wheat crop in Pakistan

  1. Yellow (Stripe Rust)
  2. Brown (Leaf Rust)
  3. Black (stem Rust)

Yellowishness in wheat due to Rust

Yellowishness in wheat occurs due to Stripe rust disease. Yellow rust is basidiomycete fungus Puccinia striiformis f. sp. tritici. Yellow rust can cause losses of up to 40 % with some field destroyed completely. Generally occur throughout wheat production areas at high elevations In northern & southern areas of temperate regions. The cool climate favours the spread of this disease. Temperature between 12-20ºC  can cause the rapidly spreading of this from infected to healthy plants.

Disease cycle

  • The fungus produces orange urediniospores 20 to 30 um in diameter that is a single source of inoculum.  Urediniospores is followed by Teliospore production in the late growing season.
  • Inoculum comes from volunteer plants 
  • Free water on leaves & temp <25 °C required for spore germination 
  • Appear in Dec, Jan, opt. temp. for disease, spreads is 12.8-18.3 °C 
  • The fungus survives between crop seasons by dormant mycelium & uredia 
  • Windblown uredospores are a secondary source of infection

Methods to check

Stripe rust first sign is the appearance of small yellow streaks followed by bright yellow postulates in conspicuous rows on leaves, leaf sheath, awns and glumes. Stripe rust is the only one of these diseases to have blister-like lesions organized into stripes on the leaves

Parts of plant infected: 

Commonly affects leaf blades, occasionally observed on heads when the disease is very severe; infection of leaf sheaths or stems is rare 

Shape and distribution of lesions: 

Small, round, blister-like lesions that merge to form stripes 

Lesion colour:

Yellow-orange 

Degree of damage:

No tearing of outer layers of plant tissue

Other symptoms

  • Small yellowish uredia appear in linear rows on the leaf
  • Uredia can also be seen on spikes
  • Yellow spore mass is exposed for wind dispersal
  • Telia appear as black patches under the surface of the leaf

Management

  • Resistant varieties (Akbar 2019, Ghazi 2019, Anaj 2017, Ujala 2016, Gold 2016, Johar 2016)
  • Control of volunteer plants
  • Cultivation of early sowing and early maturing varieties.
  • Avoiding thick sowing and heavy irrigation.
  • Destroying the weed plants and diseased tillers.
  • Avoiding heavy doses of nitrogenous fertilizers.
  •  Judicious use of potassic fertilizer help in minimizing the susceptibility of plants
  • Use fungicides (sulphur dusting), Tebuconazole, Difenaconazole, Flutriafol, propiconazole, azoxystrobin

Fayaz Hussain, Haroon Zaman Khan , Asif Iqbal, Muhammad Ashfaq Wahid and Muhammad Farrukh Saleem

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