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