Disease of sunflower

1. Stem Rot of sunflower Sclerotinia sclerotiorum.
Disease Symptoms
Initial symptoms are visible during pod development.
Leaves will wilt and turn gray-green before turning brown, curling and
dying.
Since blossoms are infected first, early stem or pod water-soaked
symptoms often initiate near colonized flowers.
In a few days diseased stem areas are killed and become tan and
eventually bleached.
Infected plant parts generally will have signs of the fungal pathogen as
white, fluffy mycelium during humid conditions and sclerotia on the
surface of or embedded in the stem tissue.

2. Environment
The pathogenic fungus Sclerotinia sclerotiorum proliferates in moist
environments.
Optimal temperatures for growth range from 15 to 21 degrees Celsius.
Life cycle
The lifecycle of Sclerotinia sclerotiorum can be described as
monocyclic, as there are no secondary inoculums produced. Under moist
field conditions, S. sclerotiorum is capable of completely invading a
plant host, colonizing nearly all of the plant's tissues with mycelium.
Under wet conditions, S. sclerotiorum will produce an abundance of
mycelium and sclerotia. Like most fungi, S. sclerotiorum prefers darker,
shadier conditions as opposed to direct exposure to sunlight. The
following spring the dormant sclerotia will germinate to produce fruiting
bodies called apothecia,

3. Management
An integrated control program that includes the following is
recommended:
(1) Use of hybrids seed with a good tolerance profile.

4. (2) Cultural practices that avoid high planting densities and a 3 to 4 year
crop rotation with non-host crops,
(3) Timely application of fungicides,
(4) Implementation of agronomic practices that can produce a
deterioration of sclerotia on the soil surface.
Foliar applications Azoxystrobin, picoxystrobin and Neem is
effective for the management of sclerotinia stem rot.
Alternaria Blight of Sunflower : Alternaria helianthi
Symptom
 Severe reduction in seed and oil yield
reported.
 The disease also affects the quality of
sunflower seeds by affecting
germination and initial vigour of the
seedlings.
 The disease is characterised by the
development of dark brown to black,
circular to oval spots varying from 0.2
to 5 in diameter.
 The spots are surrounded by necrotic
chlorotic zone with grey white
necrotic centre marked with
concentric rings.
Epidemiology and importance
Epidemics of Alternaria blight of
sunflowers are most common and severe in

5. areas that experience extended periods of
wet weather in summer accompanied by
mean daily temperatures between 25 and
30°C.
Disease cycle and dissemination: The
mycelium rests in the plant debris covering
the soil and less frequently on seeds.
Seedling blights caused by Alternaria may
develop when sunflower plants emerge in
rainy weather on Alternaria-infested land.
Alternaria spores are spread by wind and
splashing water.

Management
 Occurrence and severity of the disease depends on the season and
planting dates.

6.  Mid-September planting of sunflower remains free from the
disease.
 Foliar spray with 0.3 per cent Mancozeb four times at an interval
of 10 days controls the disease.
Alternaria blight of mustard (Alternaria brassicae)
Disease symptoms


 The disease attacks on the lower leaves as small circular brown
necrotic spots which slowly increase in size.
 Many concentric spots coalesce to cover large patches showing
blightening and defoliation in severe cases.
 Infected pods produce small, discolored and shriveled seeds.

7. Survival and spread

8.  The disease is externally and internally seed born.
 The pathogen survives through spores (conidia) or mycelium in
diseased plant debris or weed.
Favourable conditions
 Moisture (more than 70% relative humidity) coupled with warm
weather (12-25 °C ) and intermittent rains favours disease
development
White rust (Albugo candida)
Disease symptoms
 Both local and systemic infections are observed.
 In case of local infection, white creamy yellow raised pustules
appear on the leaves which later coalesce to form patches.
 In systemic infection and during humid weather, mixed infection
of white rust and downy mildew cause swelling and distortion of
the stem and floral parts due to hypertrophy and hyperplasia and
develop “stag head” structure.

9. Survival and spread
 The pathogen survives through oospores in affected host tissues
and soil.
 Secondary infection is carried out by sporangia and zoospores
which produce new infection.
Favourable conditions
 Moist (more than 70% relative humidity) coupled with warm
weather (12-25 °C) and intermittent rains favours disease
development.

10. Downy mildew (Peronospora parasitica)
Disease symptoms
 Grayish white irregular necrotic patches develop on the lower
surface of leaves.
 Later under favourable conditions brownish white fungal growth
may also be seen on the spots.

11.  The most conspicuous and pronounced symptom is the infection of
inflorescence causing hypertrophy of the peduncle of inflorescence
and develop stag head structure.
Survival and spread
 The pathogen survives as oospores on the affected plant tissues in
soil and on weed hosts.
Favourable conditions
 Atmospheric temperature in the range of 10-20 °C and relative
humidity>90% RH favours disease development
Management
Cultural Practices
Avoid irrigation during flowering.
Utilizing a longer rotation with corn and wheat has been shown to
reduce pathogen buildup and disease risk.

12. 1. Treat the seed with Apron 35 SD at the rate of 6 g/kg
of seed before sowing.
2. Spray the crop with 0.2 % Ridomil or 0.1% Karathane as soon as
the symptoms are noticed and repeat the spray two to three times at 10
days interval.
Sclerotinia Stem Rot: Sclerotinia sclerotiorum
Symptom
 The stems develop water-soaked spots which later may be
covered with a cottony white growth.
 As the disease progresses, affected portions of the stem
develop a bleached appearance, and eventually the tissues
shred.
 Girdling of the stem results in premature ripening and in
lodging of plants.
 Hard black bodies, the sclerotia, are formed inside the stem
and occasionally on the stem surface.
Survival and spread
 The pathogen survives as mycelium in dead or live plants and as
sclerotia in infected plant parts or on the soil surface or with seed as
contaminant.
Favourable conditions

13.  High humidity (90-95%) and average temperature (18-25 o
C) along with
wind current favours the disease development.

Management
 Use crop rotation; do not plant highly susceptible crops more
than once in four years.
 Use at least a five year rotation for severely infested fields.
 Avoid planting next to a field that had severe Sclerotinia in the
past four or five years. Control broad-leaved weeds.
 Plant thoroughly cleaned seed. Avoid dense stands of canola.