Broad beans crop diseases A Lecture by Mr Allah Dad Khan

2. The Broad Bean Crop
Diseases
A
Lecture To ToT trainees (
FFS)
By
Mr. Allah Dad Khan
Provincial Coordinator IPM
KPK

5. ALTERNARIA LEAF SPOT
ALTERNARIA ALTERNATA
 Small irregular brown lesions on leaves
which expand and turn gray-brown or dark
brown with concentric zones; older areas of
lesions may dry out and drop from leaves
causing shot hole; lesions coalesce to form
large necrotic patches
 Cause
 Fungus
 Comments
 Disease emergence favored by high
humidity and warm temperatures; plants
grown in nitrogen and potassium deficient
soils are more susceptible
 Management
 Plant beans in fertile soil; foliar fungicide
application may be required
Symptoms

6. ANTHRACNOSE
GLOMERELLA LINDEMUTHIANA
 Small, dark brown to black
lesions on cotyledons; oval or
eye-shaped lesions on stems
which turn sunken and brown
with purple to red margins;
stems may break if cankers
weaken stem; pods drying
and shrinking above areas of
visible symptoms; reddish
brown spots on pods which
become circular and sunken
with rust colored margin
 Cause
 Fungus
Symptoms

7. BACTERIAL WILT
 The symptoms of bean
bacterial wilt, caused by
Curtobacterium
flaccumfaciens
(=Corynebacterium
flaccumfaciens), are
similar to those of
common blight. In
addition, plants are
stunted, and leaves
droop and appear wilted.
Symptoms

8. DOWNY MILDEW
PERONOSPORA VICIAE
 Yellow-brown blotches on
upper surface of leaves;
angular patches of fluffy
white-gray fungus on
lower side of leaves;
plant growth may be
stunted or distorted and
whole plant may die
before flowering; plant
may produce
 Cause
 Fungus
Symptoms

9. POWDERY MILDEW
ERYSIPHE PISI
 Yellow spots on upper
surface of leaves;
powdery gray-white
areas which coalesce
to cover entire plant; if
plant is heavily infected
it may appear light blue
or gray in color
 Cause
 Fungus
Symptoms

10. CHOCOLATE SPOT BOTRYTIS CINEREA
BOTRYTIS FABAE

Symptoms of disease can be
aggressive or non-aggressive;
symptoms on non-aggressive
chocolate spot are small red-
brown lesions on leaves of the
plant which may also be present
on stems and pods; under high
humidity the disease moves to
the aggressive stage and lesions
coalesce and become covered in
fluffy mycelium; large patches of
tissuy can become necrotic and
die
 Cause
 Fungus
Symptoms

11. BLACK ROOT ROT
THIELAVIOPSIS BASICOLA
 Elongated red-purple lesions on root
tissue which turns dark gray to black;
lesions coalesce to form large dark
areas on roots and stems; deep
lesions can cause stunted growth,
wilting leaves, defoliation and plant
death
 Cause
 Fungus
 Comments
 Fungus survive in plant debris in soil
 Management
 Rotate crops with non-susceptible
grasses; avoid excess irrigation or
drought stress
Symptoms

12. FUSARIUM ROOT ROT
FUSARIUM SOLANI
 Young plants stunted with
chlorotic leaves; older plants with
chlorotic leaves and some leaf
drop; severely decayed roots
which are hollow and dry
 Cause
 Fungus
 Comments
 Fungus can survive in soil for
several years
 Management
 Practice long term crop rotation;
avoid over or under watering
plants; some bean varieties
exhibit some tolerance
Symptoms

13. RUST (UROMYCES FABAE)
 Rust is characterised by
numerous small reddish-
brown pustules on the
leaves.
 It is more serious on
spring beans and all
varieties are susceptible.
 Most damage occurs if
infection begins during
flowering and pod set.
Symptoms

14. WHITE MOLD (SCLEROTINIA ROT)
SCLEROTINIA SCLEROTUM
 Flowers covered in white, cottony fungal growth;
small, circular, dark green, water-soaked lesions on
pods leaves and branches which enlarge and
become slimy; cottony white growth may be visible
on lesions during periods of high humidity; death of
branches and/or entire plant
 Cause
 Fungus
 Comments
 Fungus can survive in soil for in excess of 5 years;
disease can be spread by wind, contaminated
irrigation water and by infected seeds
 Management
 There is no true immunity to white mold in any bean
varieties; rotate crops with non-hosts like cereals
and corn; plant rows parallel to direction of
prevailing winds to prevent spread of disease from
secondary hosts nearby; avoid excessive nitrogen
fertilizer; use a wide row spacing
Symptoms

15. BACTERIAL BROWN SPOT

Pseudomonas syringae
 Symptoms
 Small, dark brown necrotic spots on leaves
which may be surrounded by a zone of
yellow tissue; water soaked spots on pods
which turn brown and necrotic; pods may
twist and distort in area of infection
 Cause
 Bacterium
 Comments
 Bacterium overwinters in crop residue;
disease more severe when foliage is wet
for extended periods
 Management
 Plant only certified seed; rotate crops
regularly; remove crop debris from field
after harvest
Symptoms

16. BACTERIAL BLIGHT
XANTHOMONAS CAMPESTRIS
SYN. XANTHOMONAS AXONOPODIS
 Water-soaked spots on
leaves which enlarge and
become necrotic; spots may
be surrounded by a zone of
yellow discoloration; lesions
coalesce and give plant a
burned appearance; leaves
that die remain attached to
plant; circular, sunken, red-
brown lesion may be present
on pods; pod lesions may
ooze during humid conditions
 Cause
 Bacterium
Symptoms

17. HALO BLIGHT
PSEUDOMONAS SYRINGAE
 Small water-soaked spots on
underside of leaves which
turn necrotic and become
visible on upper surface;
lesions may develop an area
of chlorotic tissue around the
spots; lesions on expanding
leaves may cause distorted
leaves; red-brown lesions
may be visible on pods; pod
lesions may ooze or may turn
tan in color
 Cause
 Bacterium
Symptoms

18. MOSAIC
BEAN COMMON MOSAIC VIRUS (BCMV)
BEAN COMMON MOSAIC NECROSIS VIRUS (BCMNV
 Mottled dark and light green patterns
on leaves; leaves may be distorted;
yellow dots may be present on
leaves; growth of plant may be
reduced
 Cause
 Viruses
 Comments
 BCMV can be transmitted by seed
and has a worldwide distribution;
BCMNV also transmitted through
infected seed but geographic range
more restricted
 Management
 Plant only virus-free seed; plant
resistant varieties
Symptoms

19. LEAF BLIGHT
XANTHOMONAS CAMPESTRIS
SYN. XANTHOMONAS AXONOPODIS
 Water-soaked spots on
leaves which enlarge and
become necrotic; spots may
be surrounded by a zone of
yellow discoloration; lesions
coalesce and give plant a
burned appearance; leaves
that die remain attached to
plant; circular, sunken, red-
brown lesion may be present
on pods; pod lesions may
ooze during humid conditions
 Cause
 Bacterium
Symptoms

20. ROOT KNOT NEMATODE
MELOIDOGYNE SPP.
 Galls on roots which
can be up to 3.3 cm (1
in) in diameter but are
usually smaller;
reduction in plant vigor;
yellowing plants which
wilt in hot weather
 Cause
 Nematode
Symptoms

21. RHIZOCTONIA ROOT ROT
 Rhizoctonia solani is a soil-borne
fungus that attacks plants of
almost any age. This fungus
causes seed rot and damping-off
of seedlings, as well as stunting,
yellowing, and death of older
plants. Elongate, sunken, red-
brown lesions develop on roots
and stems at or below the soil
line (Figure 5). Lesions may
enlarge to girdle the stem, killing
roots and weakening the top of
the plant. Infected plants may be
stunted and leaves may turn
yellow and die.
Symptoms

22. LEAF AND POD SPOT (ASCOCHYTA FABAE)
 This produces brown spots
containing distinctive black
fruiting bodies (pycnidia).
 Autumn sown beans are more
prone to serious attacks
especially in wet conditions.
 The disease is seed-borne, air-
borne and splash dispersed.
 It is advised that farm-saved
seed should be tested by PGRO.
 Infection can be transmitted from
bean volunteers in neighbouring
fields
Symptoms