4. 1. Heavily infested fields generally appear in patches of
different sizes and often in low spots.
2. However, when conditions are very favourable for
disease incidence, the plants throughout the field may
exhibit disease symptoms
3. General symptoms are poor emergence, very uneven
growth, dead seedlings and reddish discoloration of
above-ground plant parts
Seedling diseases
6. 4. Water-soaked and necrotic area just below or at the soil line
5,6 . Wire-stem symptom
6,7. Infected roots may rot off just below the soil surface and result
in plant death and a reduced stand.
7. • Seed decay and damping-off disease
• Seed decay - Seed balls of table beets become infected
and decayed prior to germination.
• Pre emergence damping off - Very young seedlings may
also become infected and die before they can emerge
above the soil surface
• Post emergence damping off - Emerged healthy seedlings
may become infected and exhibit a water-soaked and
necrotic area just below or at the soil line .
• The latter type of infection may result in wilting, collapse,
and death of severely infected seedlings
8. Wire-stem symptoms / post emergence damping-off stage
o In 2- to 4-week-old infected seedlings that survive,
however the stem and main root regions become brown
to black partially or completely shrivelled; giving them
a thread-like appearance (wire-stem symptom).
o Seedlings with wire-stem symptoms may have normal
branching fibrous root systems, or roots that are brown
and at different stages of rotting.
o Severely infected plants are stunted and reddish-purple.
o lf plants are stressed and the infection progresses, infected
roots may rot off just below the soil surface, and result in
plant death and a reduced stand.
9. Symptoms of Aphanomyces root rot (1, 2, A,B) ,
(C) seedling damping-off
Black root rot - Aphanomyces cochlioides
10. Symptoms
Root rot two phases – Chronic and acute phase
Acute phase is referred to as black root, induces seedling
damping off several weeks after emergence
o Post emergence damping off : Greyish water soaked
spots on stem near the soil line, later turn to gray to black ,
stem become thin thread like, cotyledons seldom die
unlike the symptoms caused by Pythium, Rhizoctonia
o Chronic root rot phase is more common and occurs on
the plant early in the season
o Affected plants show temporary wilt symptoms (unlike
Rhizoctonia root rot) - leaves may become yellow,
scorched appearance, brittle
Black root rot - Aphanomyces cochlioides
11. Symptoms contd…
o Root symptoms any where on tap root but often occurs
towards the distal end
o As yellowish brown water soaked lesions , later penetrate
to the interior tissues which become dry and necrotic
o If conditions favourable for plant growth, plants may
recover and grow, how ever many roots may still exhibit
varying degrees of root distortion and scarring
o In case of severe disease incidence tap root completely
destroyed leaving little except the crown
Black root rot - Aphanomyces cochlioides
15. Rhizoctonia root rot and blight – Rhizoctonia solani
Symptoms
General symptoms
o Poor germination and seedling emergence,
o Very uneven growth,
o Dead seedlings
o Reddish discoloration of above-ground plant parts .
Specific symptoms
o Seed decay and pre emergence damping-off,
o Post emergence damping-off
o Wire-stem
o Misshapen fleshy roots with external or internal rots.
16. Rhizoctonia root rot and blight – Rhizoctonia solani
Symptoms
On plants abnormal and Infected fleshy root
o Later in the growing season, infected plants that survive the
wire-stem phase develop abnormal fleshy roots .
o Infected tissues of the root and stem enlarge more slowly than
the surrounding healthy tissues, leading to the formation of
constrictions of various shapes and sizes.
o At harvest, infected fleshy roots may exhibit several dry rot
symptoms.
o The rotted tissues are generally firm and dry, brown to black
and sharply delimited by healthy tissue .
o The rotted areas range in size from a small lesion to the whole
root.
o Infection of the fleshy roots may also occur through the petioles
in the crown area resulting in a downwardly progressing rot
17. Rhizoctonia root rot and blight – Rhizoctonia solani
Management
o Deep ploughing
o Crop rotation with non host crops like corn, barley, wheat
and oat (host crops - beans, cabbage, peas or potatoes)
o Green manuring
o Sowing on ridges will reduce damage by Pythium.
o Seed treatment with chemical fungicides (eg. carboxin,
flutolanil, iprodione, tolclofos-methyl, cyproconazole)
o Biocontrol - Pseudomonas fluorescens, Trichoderma
harzianum for the control of R. solani
19. Symptoms
o The most important sign of the disease is the presence of
white strands of fungal mycelium
o Numerous mustard seed sized sclerotia are found on the
decaying parts
o Yellowing and wilting of plants
o The fleshy roots are completely or partially decayed
o Plants can be pulled out easily
Sclerotium root rot of beet root - Sclerotium rolfsii
20. Management
o Soil drenching with 0.3% copper oxychloride or 0.25%
captan near the collar region.
o Drenching of 0.1% carbendazim should be initiated just prior
to flowering stage or Thiophanate methyl (0.1%) or Combination
of Mancozeb (0.25%) and Carbendazim.
o The fungicides hexaconazole, propiconazole,
difenoconazole; combi product, avatar (hexaconazole 4% +
zineb 68%), nativo (tebuconazole 50%+ trifloxystrobin 25%)
and vitavax powder (thiram 37.5%+carboxin 37.5%)
Sclerotium root rot of beet root - Sclerotium rolfsii
23. Sugar beet
In seedlings - Rotting of fleshy roots
In mature plants - fungus become active results in dry black rot in sugar beet
Phoma blight and heart rot: Phoma betae
24. Phoma blight and heart rot: Phoma betae
• Hosts: Table beet, sugar beet, Swiss chard, spinach,
lambsquarters (weed)
Symptoms:
• Seed rot and damping off in young seedlings.
• If survived the seedling stage infection, rotting of fleshy
roots is observed.
• Foliar symptoms include tan-brown leaf spots with dark
concentric rings .
• Pycnidia produced in dark concentric rings within the lesion
• Root symptoms include dark brown and dry lesions
associated with shrinking.
• Phoma root rot typically begins in the center of the crown
and spreads downward into the taproot (unlike
Aphanomyces root rot).
25. Phoma blight and heart rot: Phoma betae
Disease Cycle:
• P. betae is commonly introduced into fields through
seed .
• The pathogen can be spread within a field through
water-splashed conidia, surviving in the soil on
infested plant debris, and on alternative weed hosts.
• The pathogen can be spread farther distances
between fields through windblown ascospores.
26. Management
• Use treated and certified seed
• Practice crop rotation (3 years)
• Dispose of plant residues after harvest
• Grow beets in well fertilized soils using clean seed
• Hot water treatment of seeds at 590C for 8 min
followed by drying for 24 h and retreat with thiram @
5g/kg seed
• Application of boron and sodium
Phoma blight and heart rot: Phoma betae
27. Cercospora leaf spot (CLS) :Cercospora beticola
• This is most important disease affecting table beet.
• In processing table beet crops, epidemics cause
significant defoliation and may disrupt mechanized
harvest.
• For fresh market table beet production, roots may be
sold with or without intact foliage.
• The lesions on the foliage may lead to rejection for
fresh market sale.
30. Cercospora leaf spot (CLS) :Cercospora beticola
Symptoms
o The lower leaves near the ground are attacked first.
o Disease symptoms are initially discrete, necrotic
lesions in red table beet cultivar lesions margins are
red to purple
o In yellow cultivar - lesions margins are tan brown .
o Lesions have a grey centre on all cultivars
o Central tissue turns brown and assumes grayish
colour after sporulation
o The spots dry up giving a shot hole appearance
31. Symptoms contd…
o Elongated spots appear on petioles
o Spots coalesce, the leaves wrinkle and dry.
o As leaves die, the crown becomes cone-shaped with a
rosette of dead leaves at the base.
o Defoliation occurs throughout the growing season
resulting in reduction in root size and yield.
o Older leaves are mostly affected
o Reduction in root growth, yield and sugar content
Cercospora leaf spot (CLS) :Cercospora beticola
33. Disease cycle
Alternate Hosts - swiss chard, spinach, and sugar beet.
Commonly encountered weeds Lambsquarters, Pigs weed
also serve to perpetuate the fu ngus.
Soil and Plant Residues: Cercospora beticola is able to
survive in the soil on infested plant residues for up to 3
years.
Cercospora leaf spot - Cercospora beticola
34. Management
• Reducing the periods of leaf wetness by decreasing planting
densities and orienting rows parallel to the prevailing wind
direction can be very helpful in minimizing the pathogen
infection.
• Sanitization by removing infected leaves, plant debris and
weeding can help manage disease.
• Mulching can be a good approach for limiting the weeds in the
field
• Tillage methods also have been found to affect the disease
development
• Spraying Chlorothalonil 1.5 ml/lit, Copper hydoxide 2g/l,
Propiconazole 1.0 ml/lit ,Iprodione + Carbendazim 2g/l,
Mancozeb+carbendazim 2g/l, Azoxystrobin 23% SC @ 0.1%,
Kresoxim methyl 44.3% SC @ 0.1%, Pyraclostrobin + Metiram 60%
WG @ 0.2%
Cercospora leaf spot - Cercospora beticola
37. Symptoms
• Mottling of leaves with occasional ring like lesions
• On garden beets, vein clearing
• Infected foliage is leathery, stunted and distorted
• Leaves can become thicker and then brittle
• Reduction in size of petioles
• Roots are smaller with hairy side roots
Beet yellows – Beet Yellows Virus, Beet Mild Yellowing Virus (BMYV)
38. Beet yellows – Beet Yellows Virus, Beet Mild Yellowing Virus (BMYV
o Gram +ve, ss RNA
o Closterovirus group.
o Closteroviridae
o Longest viruses, Flexious rods
o Beet Mild Yellowing Virus make the plants more susceptible to
fungal attack (Powdery mildew).
40. Management
• Removal and destruction of weed hosts
• Plants selected for seed plants should be free of
virus and grown in isolation
• Vector control with insecticides
Beet yellows – Beet Yellows Virus, Beet Mild Yellowing Virus (BMYV)
Editor's Notes
Symptoms- Infection is confined to older leaves in vegetative stage. Light brown to black necrotic areas with grayish centers is observed on leaves. Pycnidia are arranged in concentric rings on central grayish area, Rotting of fleshy roots in seedling stage
When plants mature, fungus become active and causes dry black rot in sugar beet
Symptoms- Infection is confined to older leaves in vegetative stage. Light brown to black necrotic areas with grayish centers is observed on leaves. Pycnidia are arranged in concentric rings on central grayish area, Rotting of fleshy roots in seedling stage
When plants mature, fungus become active and causes dry black rot in sugar beet
When roots are to be stored, follow close topping
Beet root
The lower leaves near the ground are attacked first.
The spots are small, circular ash coloured in the centre with deep violet or reddish-purple borders
Central tissue turns brown and when sporulation occurs spot assumes a grayish
Elongated spots appear on petioles
Reduction in root growth, yield and sugar content
They coalesce to form bigger and the leaves wrinkle and dry.
The spots dry up giving a shot hole appearance to the leaves.
When spots are numerous, leaves become blighted and defoliate under favourable conditions
Nutrient including macro and micronutrient supply management.
Acyrthosiphon dirhodum, The black bean aphid (Aphis fabae) can also spread BYV but not BMYV
