Diseases of horticultural crops

1. .
DISEASES OF FENUGREEK
STUDENT COURSE TEACHER
Valandina.N Dr.Parthasarathy.S
ID.NO:2015021135 Asst. Prof. (Plant Pathology)

2. Diseases of Fenugreek
 Cercospora leaf spot: Cercospora traversiana
 Charcoal rot: Macrophomina phaseolina
 Powdery mildew: Erysiphe polygoni, Leveillula taurica
 Downy mildew: Peronospora trigonellae
 Rust: Uromyces trigonellae

3.  Root rot /collar rot/ Foot rot : Rhizoctonia solani,
Sclerotium rolfsii
 Damping off : Pythium aphanidermatum
 Fusarium wilt: Fusarium oxysporum
 Yellow mosaic disease: Bean yellow mosaic virus

4. 1. Cercospora leaf spot
Pathogen name
Cercospora traversiana

5. Disease symptoms
Circular sunken lesions with chlorotic halos on
leaves; necrotic areas on leaves and discolored areas
on pods.
Pathogen survives mainly in plant debris as desiccation-
resistant pseudostromata, but can also survive as conidia
in debris or seeds.
When moisture is sufficient, new conidia are formed and
spread via rain-splash or wind to new leaves or plants.

6. Systematic position
Kingdom : Fungi
Division : Ascomycota
Class : Dothideomycetes
Order : Capnodiales
Family : Mycosphaerellaeae
Genus : Cercospora
Species : Cercospora traversiana

7. Favourable conditions
 Optimum conditions are 25°C to 35°C with night
temperatures above 16°C, and a relative humidity of
90-95%.
 Infection is greatly reduced or nonexistent at
temperatures less than 15° C or during periods of leaf
wetness less than 11 hours.

8. Management
 Spray Blitox @ 0.3%.

9. 2. Charcoal rot
Pathogen name
Macrophomina phaseolina

10. Disease symptoms
Cankers on stem may spread upwards; leaves may wilt
and drop from plant.
Numerous small black sclerotia (fungal fruiting
bodies) develop in affected tissues and can be used to
diagnose the disease.

11. Systematic position
Kingdom: Fungi
Division: Ascomycota
Class: Dothideomycetes
Order: Botryosphaeriales
Family: Botryosphaeriaceae
Genus: Macrophomina
Species: Macrophomina phaseolina

12. M. phaseolina survives as microsclerotia in the soil
and on infected plant debris.
The microsclerotia serve as the primary source of
inoculum and have been found to persist within the
soil up to three years.
PATHOGEN

13. Favourable conditions
 Hot, dry weather promotes infection and development
of charcoal rot.

14. 3. Powdery mildew
Pathogen name
Erysiphe polygoni, Leveillula taurica

15. Disease symptoms
 White, powdery spots on leaves which expand over
time.
 Yellow spots may be visible on leaf underside.

16. © eAgriculture

17. Pathogen
 The disease is caused by Erysiphe polygoni.
 Fungus Oidiopsis taurica (imperfect stage of Leveillula
taurica) has also been reported to be associated with this
disease.
 The mycelium of Erysiphe is generally fine and persistent,
rarely thick.
 The haustoria develop as outgrowths from lobed swellings.
The haustorium penetrates the cell wall and forms a sac in the
epidermal cell.

18.  Conidiophores arise vertically and each bears several
spores in chain.
 In dry temperate zone, perithecia appear as sharp
black specks, scattered on the surface of the white
mycelium.
 During favourable season, they disintegrate and
liberate ascospores which germinate and infect the
new crop.

19. Disease cycle
© AESA based IPM in Fenugreek

20. Favourable conditions
 Humidity is an important factor related to the onset
and spread of powdery mildew.
 High relative humidity favors spore formation, and
low relative humidity favors spore dispersal, which
explains why powdery mildew tends to be a problem
when the days are cool and the nights are humid.

21. IDM
 Dust Sulphur at 25 kg/ha or foliar spray with wettable
sulphur 2 g/lit at the time of appearance of disease.
 Use resistant variety like Prabha. Lines GC-39UM-
32, GC-7, GC-20 and UM-34 have also been reported
as resistant and can be utilized in breeding
programme.

22.  With the initiation of the disease spray the crop with
wettable sulphur (0.2%), or hexaconazole (0.05%) or
dinocap (0.06%) or difenoconazole (0.04%) and
repeat at 10-14 days interval.
 Sow the crop by the end of the October.

23. 4. Root/ Collar / Foot rot
Pathogen name
Rhizoctonia solani , Sclerotium rolfsii

24. Disease symptoms
Rhizoctonia root rot develops from infection of the growing tip
of small lateral roots. The fungus then progressively grows from
the root tip and may cause rot of the main root. Rhizoctonia
infection of a rootlet often results in the spear-point symptom of
roots.
Small chlorotic, water-soaked lesions appear randomly over both
surfaces of the leaflets. They enlarge, become irregular in shape,
and are brown with darken brown margins. The central portion
later become pale, dry rapidly and disintegrate.

25. © eAgriculture

26. Survival and spread
 They survive in soil for long periods in the absence of
a host, and inoculum levels in soil increase slowly
over several years (crop cycles).
Favourable conditions
 High humidity and warm weather favours the
development of disease.

27. IDM
 Root rot can be controlled by soil application of
Neem cake @ 150 g/ha and seed treatment with
Trichoderma viride @ 4g/kg of seed and drenching
with Carbendazim 0.5 g/l or Copper oxychloride 2
g/litre.
 Follow 3-4 years crop rotation.

28.  Soil amendment with neem cake (1 t/ha) alone and in
combination with Trichoderma reduces root rot.
 Seed treatment with carbendazim (0.2%) followed by
drenching @ 0.1 per cent effectively controls this
disease.

29. 5. Downy mildew
Pathogen name
Peronospora trigonellae

30. Disease symptoms
 The symptoms of downy mildew are quite distinct
from the other diseases.
 The adaxial surfaces of the leaves showed yellow
patches or small chlorotic spots which appear often at
the margins.
 The abaxial surface of the leaf showed white cottony
mycelial growth which often appears as grayish
violet.

31. Survival and spread
 The fungus survives in plant parts and plant debris
such as fallen leaves.
Favourable conditions
 The disease is favored by a maximum temperature
range of 18-24˚C to minimum temperature range of
4-10˚C and a relatively high humidity which is more
than 80%.

32. Management
 This disease can be controlled by spraying of 20g
solution of Difoltan or any other copper fungicide.

33. 6. Rust
Pathogen name
Uromyces trigonellae

34. Disease symptoms
 Rust commonly appears as a colored powder, consisting
of minute aeciospores that land on the fenugreek plant
generating pustules (uredia) on the ventral leaf surface.
 During late spring or early summer of the disease cycle,
yellowish orange to dark brown, hair-like (ligulate)
structures called telia develop on the leaves.
 Small, round or oblong, dark brown pustules on the
leaves and petioles are commonly observed.

35. Spread and survival
 The fungus mainly survives through teliospores (thick
walled, resting spores) on leaves left in the field or on
the soil surface.
 The disease spreads by wind-borne uredospores from
infected crop.

36. Favourable conditions
 Temperature ranging from 20 to 25° C with relative
humidity of 86-92% RH favours high intensity of
rust.

37. 6. Damping off
Pathogen name
Pythium aphanidermatum

38. Disease symptoms
The emerged seedlings exhibit water soaked
discoloured, soft basal rot of the stem due to the death
of cortical tissues.
The rotted seedlings emit bad odour, the whole
seedling topples over

39. Survival and spread
 The fungus survives in soil. Primary infection occurs
through soil and secondary by conidia through rain or
wind.
 High humidity, high soil moisture, cloudiness and low
temperatures below 24°C for few days are ideal for
infection and development of disease.
 Crowded seedlings, dampness due to high rainfall, poor
drainage and excess of soil solutes helps establishment.

40. Disease name
Fusarium wilt
Pathogen name
Fusarium oxysporum

41. Disease symptoms
 First seen as minor clearings in veins on young
leaflets finally accompanied with downward drooping
of mature leaves.
 At the seedling stage, plants may wilt and die soon
after the appearance of the symptoms.
 In mature plants, vein clearing and downward
drooping of the leaf followed by stunting, yellowing
and wilting.

42.  This is followed by marginal necrosis of the infected
leaves, rapid defoliation and death of the plant. In
addition, browning of vascular tissue occurs.
 These symptoms become more prominent in mature
plants during the period between blossoming and fruit
maturation.

43. Survival and spread
 The disease is soil borne and primary infection occurs
through inoculum present in the soil.
Favourable condition
 Relatively high soil moisture and soil temperature are
favourable for the infection.

44. 7. Yellow mosaic disease
Pathogen name
Bean yellow mosaic virus

45. Disease symptoms
 Mosaic virus disease with symptoms of vein clearing,
severe mottling, leaves curled at the margin and reduced
leaf size.
 Pods if formed are very small, curled with thin and
shrunken seeds.
 The disease is transmitted in semi persistent manner by
aphid.
 Aphids are more active in warm conditions and increase
their population as well as spread the virus.

46. References
 https://www.researchgate.net
 agritech.tnau.ac.in>horticulture>
 https://niphm.gov.in>IPMPackages>
 Gupta, S.K., Monica Sharma and R.C.Sharma, 2017, Diseases
of vegetables, Ornamental and Spice crops, Scientific
publishers, New Delhi.