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.