Horsegram Diseases

Cercospora leaf spot

Disease symptoms:

• Moist weather and splashing rains are conducive to disease development. Most outbreaks of the disease can be traced back to heavy rainstorms that occur in the area.
• Infected leaves show small, brown, water soaked, circular spots surrounded with yellowish halo.
• On older plants, the leaflet infection is mostly on older leaves and may cause serious defoliation. The most striking symptoms are on the green fruit.
• Small, water-soaked spotsfirst appear which later become raised and enlarge until they are one-eighth to one-fourth inch in diameter.
• Centres of these lesions become irregular, light brown and slightly sunken with a rough, scabby surface.
• Ripe fruits are not susceptible to the disease. Surface of the seed becomes contaminated with the bacteria, remaining on the seed surface for some time.
• The organism survives in alternate hosts, on volunteer horsegram plants and on infected plant debris.

Survival and spread:

• The fungus survives on diseased plant debris .Fungus spreads about 3 m through the soil in one season.

Favourable conditions

• Moist weather and splashing rains.
• High humidity or persistent dew

Bacterial leaf spot

Disease symptoms:

• This is a common disease of horsegram occurring on the foliage at any stage of the growth.
• The pathogen attacks the foliage causing characteristic leaf spots and blight. Early blight is first observed on the plants as small, black lesions mostly on the older foliage.
• Spots enlarge, and by the time they are one-fourth inch in diameter or larger, concentric rings in a bull's eye pattern can be seen in the center of the diseased area.
• Tissue surrounding the spots may turn yellow. If high temperature and humidity occur at this time, much of the foliage is killed.
• Lesions on the stems are similar to those on leaves, sometimes girdling the plant if they occur near the soil line.

Survival and spread

• The bacterium is seed-borne

Favourable conditions

• Rain splashes play an important role in the development and spreadof the disease.
• Warm, rainy and wet weather is congenial

Anthracnose

Disease symptoms:

• Symptoms are circular, black, sunken spots with dark center and bright red orange margins on leaves and pods
• In severe infections, the affected parts wither off.
• Seedlings get blighted due to infection soon after seed germination.

Survival and spread

• The pathogens survive on seed and plant debris
• Disease spreads in the field through air-borne conidia

Favourable conditions

• The disease is more severe in cool and wet seasons.

Root rot

Disease symptoms:

• The pathogens cause seed decay, root rot, damping-off, seedling blight, stem canker and leaf blight in horsegram
• The disease occurs commonly at pod development stage
• The affected leaves turn yellow in colour and brown irregular lesions appear on leaves.
• Roots and basal portion of the stem become black in colour and the bark peels off easily.
• When the tap root of the affected plant is split open, reddening of internal tissues is visible.

Survival and spread

• Species are saprotrophic, occurring in the soil which is the source of primary infection.
• Secondary infection occurs by means of asexual spores.

Favourable conditions

• Moist soil and humid conditions favour the development of disease.

Mosaic complex

Disease symptoms:

• Initially mild scattered yellow spots appear on young leaves
• The next trifoliate leaves emerging from the growing apexshow irregular yellow and green patches alternating with each other
• Spots gradually increase in size and ultimately some leaves turn completely yellow
• Infected leaves also show necrotic symptoms.
• Diseased plants are stunted, mature late and produce very few flowers and pods
• Pods of infected plants are reduced in size and turn yellow in colour.

Transmission and Favourable conditions

• The disease is transmitted in semi persistent manner by aphids and whiteflies.
• Aphids are more active in warm summer conditions and increased their population as well as spread the viruses .

Powdery mildew

Disease symptoms:

• White powdery patches appear on leaves and other green parts which later become dull coloured
• These patches gradually increase in size and become circular covering the lower surface Also. 30
• When the infection is severe, both the surfaces of the leaves are completely covered by whitish powdery growth.
• In severe infections, foliage becomes yellow causing premature defoliation.
• The disease also creates forced maturity of the infected plants which results in heavy yield losses.

Survival and spread

• The pathogen has a wide host range and survives in oidial form on various hosts in offseason
• Secondary spread is through air-borne oidia produced in the season.

Favourable conditions

• Dry and moist weather (90% RH) favours disease development

IPM for Horsegram

To know the IPM practices for Horsegram, click here.

Source: NIPHM; Directorate of Plant Protection, Quarantine & Storage