DISEASE OF FIELD CROPS

1. DISEASE OF FIELD
CROPS &THEIR
MANAGEMENT
ASSIGNMENT TOPIC: DISEASE OF WHEAT
PRESENTED BY: G.SRINIDHI
DAG-A
111718012019

2. DISEASES OF WHEAT
• LOOSE SMUT OF WHEAT
• KARNAL BUNT OF WHEAT
• POWDERY MILDEW OF WHEAT

3. LOOSE SMUT OF WHEAT
Casual organism: Ustilago nuda tritici
Vernacular name: Godhuma vaduluga unde smat
SYMPTOMS:
. It is a seed borne disease
. The entire inflorescence is commonly affected and appears
as a mass of olive –black spores ,initially covered by a thin
grey membrane.
.Once the membrane ruptures, the head appears powdery.

4. SURVIVAL AND SPREAD
• The disease is internally seed borne, where pathogen
infects the embryo in the seed.
• Primary infection occurs by sowing infected seeds.

5. FAVOURABLE CONDITIONS
• Infection is favored by cool, humid conditions during flowering
period of the host plant.
• MANAGEMENT PRACTICES:
• Disease control: The disease is internally seed borne and as
such spray of fungicides is not effective in controlling the
disease.
• Seed treatment: Use of resistant varieties, crop rotation at
suitable intervals is also effective in disease control, hot water
treatment where seeds are soaked in water for five hours at 20°C,
the water is drained off and then they are treated with hot water
at 49°C for about a minute and finally with hot water at 52°C for
11 minutes. By this method the dormant mycelium inside the
seed dies off by this treatment.
• Use of systemic fungicides: Several fungicides like carboxin,
vitavax and benlate@ 2.0 g/kg seed. A combination of vitavax with
thiram is very effective for disease control.

6. KARNAL BUNT OF WHEAT
• Casual organism : Neovassia indica .
• Intially the disease is reported as Neovassia indica(Mitra) in
1940,then it is called as Tilletia indica Mitra in 1953
• SYMPTOMS:
• Karnal bunt is difficult to identify in the field. Developing wheat kernels are
randomly infected and usually only partially converted to the fungus and hence
,called “partial bunt”.
• The disease is not usually noticed until the grain is threshed and partially
smutted kernels are exposed . Generally a few florets per spike are affected.
• While diseased seeds usually retain a partial seed coat, the embryo and part of
the endosperm have been converted to masses of small black spores which
emit a fishy odour trimethylamine.

7. PATHOGEN CHARACTER
• Teliospores are dark brown to black in color.
• Ellipsodial to spherical in shape.

8. DISEASE CYCLE
• On germination, each teliospore produces promycelium which
bears 110–185 primary sporidia at its tip. The primary sporidia
are sickle shaped and were regarded as infective entities.
Secondary sporidia (allantoid and filiform) play an important role
in the disease cycle of the pathogen. The allantoid sporidia are
pathogenic while filiform sporidia increase the inoculum by
division on host/soil surface. The sporidia are binucleate.

9. FAVOURABLE CONDITIONS
• Temperature of 18-20°C .
• High soil moisture.
• Moderate rains.
• MANAGEMENT PRACTICES:
• Disease control: The disease spread is through seed and soil borne.
• Use of resistant varieties: HD-2428,PBW-435,
• Crop rotation.
• Mulching.
• Controlled irrigation.
• Changing of sowing time.
• Seed treatment:

10. MANAGEMENT PRACTICES
• HOT WATER TREATMENT: Seeds are soaked in water for five
hours at 20°C,the water is drained off and then they are treated with
hot water at 49°C for about a minute and finally with hot water at
52°C for 11 minutes
• Use of systemic fungicides: Fungicides like carboxin,
vitavax@2.0 g/kg seed are used for seed treatment to reduce the
pathogen infectivity.

11. POWDERY MILDEW OF WHEAT
• CASUAL ORGANISM: Erysiphe graminis var. tritici.
• SYMPTOMS: Greyish white powdery growth appears on the
leaf sheath, stem and floral parts. Powdery growth later become
black lesion and cause drying of leaves and other parts.
•

12. PATHOGEN
• Fungus produces septate, hyaline mycelium on leaf surface
with short conidiophores. The conidia are elliptical, hyaline,
single celled, thin walled and produced in chains. Dark
globose cleistothecia containing 9-30 asci develop with oblong,
hyaline and thin walled ascospores.

13. DISEASE CYCLE
• Fungus remains in infected plant debris as dormant mycelium
and asci. Primary spread is by the ascospores and secondary
spread through airborne conidia.
• FAVOURABLE CONDITIONS: The disease infects plants during
periods of high humidity and cool temperatures (20-21°C).
• MANAGEMENT PRACTICES:
• Burning of crop stubbles
• Deep ploughing in summer months.
• Apply recommended dose of fertilizers.
• Use resistant varieties : BL1413,Aditya, Gautam , WK 1204
• Spray Wettable Sulphur 0.2% or Carbendazim @ 500 g/ha