Bean DiseasesA
Lecture To ToT trainees ( FFS) By
Mr. Allah Dad Khan Provincial Coordinator
IPM KPK MINFAL Pakistan
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
ANTHRACNOSEGLOMERELLA 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
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
DOWNY MILDEWPERONOSPORA 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
POWDERY MILDEWERYSIPHE 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
CHOCOLATE SPOT BOTRYTIS CINEREABOTRYTIS 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
BLACK ROOT ROTTHIELAVIOPSIS 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
FUSARIUM ROOT ROTFUSARIUM 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
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
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
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
BACTERIAL BLIGHT XANTHOMONAS CAMPESTRISSYN. 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
HALO BLIGHTPSEUDOMONAS 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
MOSAICBEAN 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
LEAF BLIGHT
XANTHOMONAS CAMPESTRISSYN. 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
ROOT KNOT NEMATODEMELOIDOGYNE 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
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
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