This document summarizes 10 major diseases that affect wheat crops: stem rust, leaf rust, stripe rust, loose smut, flag smut, common bunt, Karnal bunt, Fusarium head blight, powdery mildew, and yellow ear rot. For each disease, the causal organism is identified and brief descriptions of symptoms and management strategies are provided. The management strategies discussed include using resistant varieties, cultural practices like removing volunteer wheat, seed treatments, fungicide application, and hot water treatment or solar heating to control smut diseases.

1. PAT 302 Diseases of field &
horticultural crops & their
management – II (2+1)
DISEASES OF WHEAT

2. Major Diseases in Wheat
Diseases Causal organism
Black rust / Stem rust Puccinia graminis f. sp. tritici
Leaf rust Puccinia triticina (formally Puccinia
recondita)
Stripe rust Puccinia striiformis
Loose smut Ustilago tritici (Syn. U. nuda var. tritici)
Flag Smut Urocystis agropyri
Commonbunt/stinking bunt Tilletia caries (syn: T. tritici)
Karnal bunt/partial bunt Tilletia indica (Syn: Neovossia indica)
Fusarium head blight Fusarium graminearum (Imperfect stage)
Gibberella zeae (Perfect stage)
Powdery mildew Blumeria graminis f. sp. tritici
Tundu/yellow ear rot Rathayibacter tritici (Clavibacter michiganese
pv. tritici) + Anguina tritici

3. 1. Stem rust (Black rust)
Puccinia graminis f.sp. tritici
• Early Romans & Greeks (Robigus & Robigo)
• Heterrocious, macrocyclic, obligate parasite
• Brown elongated pustules – stem, leaf sheath,
leaf blade & glumes
• K.C. Mehta – Northern hills & Nilgiri hills
• 5 Stages
0 – Pycnial
1 – Aecial Alternate host
2 – Uredo
3 – Telial Wheat
4 – Basidial - Inactive substrate

4. Stem rust (Black rust)
Puccinia graminis f.sp. tritici

5. Stem rust (Black rust)
Puccinia graminis f.sp. tritici
1
0
2
3
4

7. 2. Leaf rust (Brown or orange rust)
Puccinia triticina (formally Puccinia recondita)
• Circular to oval, orange-brown pustules
• Raised above the leaf surface and upper surface

8. 3. Yellow rust / stripe rust
Puccinia striiformis f. sp. tritici

11. Control or Management of rust
Resistant Varieties
The best way to control leaf rust is to grow resistant varieties.
Cultural Practices
Heavy grazing or the use of herbicides during autumn to remove self-sown
susceptible wheat will reduce the amount of rust in following crops.
Seed Treatments
There are seed treatments available which will suppress early infections of
leaf rust. Seed treatments are important in susceptible varieties, especially if
they are sown early or following a wet summer favouring growth of
volunteers.
Monitoring and fungicide spray
Spray (azoxystrobin + propiconazole)/(Tebuconazole +
Trifloxystrobin)/azoxystrobin/(azoxystrobin + tebuconazole) @ 0.2% at 7 to
10 days from flag leaf emergence to early dough grain development stage or
at earliest sign of rust pustules development.

12. 4. Loose Smut
Ustilago nuda tritici
• Earhead stage
• Early emergence
• All spikelets - mass of
black powdery spores
• Blown off by wind
• Internally seed borne

14. Management
Hot water treatment (Jensen, 1886)
• Soak the seeds in cool water for 4 hours followed
by soaking in hot water (54C) for 10 min
Solar heat treatment (Luthra, 1953)
• Soak the seeds in cool water for 4 hours (8 am –
12 Noon) followed by spreading the seeds in
bright sun (44C) for 4 h (12 Noon – 4 pm).

15. Management
• Grow resistant varieties (Kalyansona, C 302,
PV 18 and WG 307)
• Seed treatment with carboxin, triadimenol,
carbendazim or benomyl 2 g/kg of seed
• Seed treatment with azole fungicides such as
difencoconazole, propiconazole or
tubuconazole 2g/kg of seed

16. 5. Flag Smut
Urocystis agropyri
• Greyish black linear sori
occur on the leaf blade
and leaf sheath
• Twisted leaves, that
droop down giving
flagging symptom
• Smut spores
(teliospores) in soil

18. 6. Common bunt/stinking bunt/hill bunt
Tilletia caries
• Symptoms evident only at heading stage
• Systemic infection
• Infected plants are shorter
• Produce a fishy stink smell
• Volatile compound – trimethylamine
• Smutted grains are covered with membrane
made up of host tissue

19. Common bunt/stinking bunt/hill bunt
Tilletia caries

21. 7. Karnal bunt/partial bunt
Tilletia indica (Syn: Neovossia indica)
• Time of earhead formation
• Partially converted into black powdery mass of
smut sorus - Partial bunt
• Embryo is not affected – Germination

23. Karnal bunt/partial bunt

24. Stinking bunt Vs Kernal bunt

25. 8.Fusarium head blight / scab
Fusarium graminearum (Gibberella zeae)
• Premature bleaching of one or more spikelets
• Entire ear head is bleached
• Sterile / shriveled and discoloured seed
• Deoxynivalenol (DON, vomitoxin)

26. Fusarium head blight / scab
Fusarium graminearum (Gibberella zeae)

27. Fusarium head blight / scab
Fusarium graminearum (Gibberella zeae)

28. 9. Powdery Mildew
Blumaria graminis var. tritici
• Greyish white powdery growth on the upper
surface of the leaf, leaf sheath &
inflorescence.
• Black dots representing the cleistothecia
formation on the affected plant parts

29. Powdery Mildew
Blumaria graminis var. tritici

30. Management
• Dust sulphur 25 kg/ha or wettable sulphur
2.5kg/ha
• Any one of the systemic fungicides - triazole
group (tridimefan, triadimenol, etaconazole,
flusilazole, myclobutanil, penconazole,
hexaconazole,propiconazole and
cyproconazole)

31. 10. Tundu / Yellow Ear Rot
Anguina tritici + Rathayibacter tritici (Clavibacter michiganese pv. tritici)
• Yellow slime on the
stem & inflorescence
• Curling and twisting of
the spikes
• Galls formed by the
nematodes replace
most of the grains in
the earhead

32. Questions?