Phytophthora blight of pigeonpea is caused by the soil-borne fungus Phytophthora drechsleri f. sp. Cajani. It was first reported in India in 1966 and causes leaf lesions, stem cankers, and plant death, resulting in potential yield losses of 5-10%. The disease is favored by warm, humid conditions with heavy rainfall and affects pigeonpea plants at any growth stage. Management strategies include crop rotation, drainage improvement, resistant varieties, and fungicide seed treatments or foliar applications.

1. Phytophthora blight of
Pigeonpea
Teksingh chandravansh
(Plant Pathology)
S.K. College ofAgriculture and Research Station
Kawardha (Kabirdham) – 491995 (C.G.)

2. Phytophthora blight of Pigeonpea
• Phytophthora blight of Pigeonpea incited by Phytophthora
drechsleri f. sp. Cajani.
• It was first reported in 1966 from India and is currently
considered to be more important in short‐duration pigeonpeas
than in traditional medium‐ and long‐duration types.
• It is a potentially important disease of Pigeonpea after
fusarium wilt and Pigeonpea sterility mosaic disease.
• It is reoccurring as an economically important disease in area
where excessive rains fall within a short span of time and hot
and humid weather persists during the crop season.

3. • It is a major production constraint to pigeonpea in India that
kills young plants.
• However, it is the most important production constraint in
north-eastern India.
• The disease occurs throughout India.
• The disease has also been reported from other countries.
• Yield losses of 5-10% has been reported from this disease

4. SYMPTOMS
• The pathogen affects the crop at any growth
stage under environmental conditions suitable
for disease development.
• Symptoms appear on the primary and trifoliate
leaves as brown to black lesions which
subsequently become necrotic within 3 days.
• The leaflet lesions are circular to irregular and
up to 1 cm diameter.
• The whole foliage can exhibit a blighted
appearance under conditions of high humidity.
• Phytophthora blight resembles damping off
disease as the seedlings die suddenly.

5. • On stems and petioles, brown to
dark brown lesions are formed near
ground level.
• Stem lesions initially have a flat
surface but later become sunken.
• They enlarge in size and girdle the
stem.
• In some cases girdling of the stem is
noticed even 1 to 1.5 m up the stem.
• The lesions on stem and branches
increase rapidly.
• Portion of the plant above the lesion
are dry out but remain but remains
attached to the plants.

6. • Later main stems or branches are
breaks up easily at this point of
infection by wind.
• Infected leaves lose turgidity,
and become desiccated.
• Stems swollen at ground level
are also common.
• It subsequently develops into
cankerous structures at the edges
of the lesions, and sometimes
lesion areas crack and shred.
• Stem lesions are often centre on
a leaf scar or site of branch
in each
initiation and extend
direction from the apparent
invasion point.

7. • As the disease progresses, patches of diseased plants become
conspicuous in the field which are visible even from a distance.
• When conditions are favourable, infected plants many die.
• The roots of Phytophthora blight-infected plants remain healthy.

8. PATHOGEN
• It is caused by Phytophthora
drechsleri f.sp. cajani.
• Mycelium coenocytic, hyphal swellings.
• Sporangiophores are usually narrow but
sometimes widen just below the
sporangium.
• Sporangia vary in shape from broadly
obpyriform to elongated obpyriform, ovoid
to elongate. They are nonpapillate and
persistent on the stalk.
• Antheridia are amphigynous; oogonia have
tapered bases and are 22 to 53 µm in
diameter.
• Oospores are plerotic and 17 to 50 µm in
diameter.

9. Disease cycle
• The disease is soil borne.
• The fungus survives as dormant mycelium in soil and in infected plant
debris.
• Sporangia are formed on phyphae and released zoospores.
• These zoospores are act as primary source of inoculum and which are
dispersed by wind over short distances during rains.
• Zoospores germinate by germ tube and caused infection on the surface of
the plants.
• Develop the symptoms and produce sporangia.
• Sporangia germinate either directly or by production of zoospores.
• Sporangia and zoospores are disseminated by the wind.
• Sporangia and zoospores act as a secondary inoculum which causes
secondary infection on the plants.

10. Epidemiology
• Soils with poor drainage
• The disease incidence was relatively higher in Alfisols than Vertisols.
• Deficiency of potassium (K), high doses of nitrogen (N) increased disease
incidence.
• Low lying areas
• Heavy rain.
• Temperature 28-30o C.
• Cloudy weather and drizzling rain and temperature of 28-300C and leaf wetness of
8hrs favorable for disease development.
• Warm and humid weather following infection results in rapid disease development.
• Relative humidity 75-96% is coupled with 300 mm rain fall within a week

11. Management
Cultural control:
• Use of pathogen-free seed,
• Adopt the crop rotation with non-host crops like bajra, sorghum etc.
• Maintain adequate field drainage.
• Select fields with no previous record of blight.
• Avoid sowing pigeonpea in fields with low-lying patches that are prone to
water-logging.
• Sow pigeonpea on ridges and provide good drainage.
• Use wide inter-row spacing, crop rotation and intercropping with short
legumes.
• Use potassium fertilizers.
• Avoid sowing red-gram in fields with low-lying patches that are prone to
water logging.
• Deep ploughing in Summer

12. Varietal Management:
• Cultivars KPL 96053, ICPL 99044, ICPL 99044, 99055, 99099, 93179,
BDN 627, Sehore 197, Sehore 197-1, ICPL 187-1, ICPL 84052, ICPL
84023 and ICPL 88009, Hy 4, ICPL-150, ICPL-288, ICPL-304, KPBR 80-
1-4, KPBR 8-2-1 were found resistant against disease.
Biological Control
• Seed treatments with T. viride or T. hamatum or B. subtilis @ 10g per kg
seed.
Chemical control:
• Seed treatment with 4 g metalaxyl MZ or mancozeb + metalaxyl or captan,
thiram or carbendazim per kg of seed .
• Foliar spray with metalaxyl or mancozeb + metalaxyl @ 0.3% at weekly
intervals.