1. WILT – Fusarium oxysporum f.sp. udum
Symptoms
The characteristic symptoms of the diseases are yellowing and dropping of leaves followed by drying of the plant and dark – streaks under the bark of roots and base of the stem. The vascular tissues exhibit brown discolouration and partial wilting of roots. The symptoms appear when the plants are at flowering and podding stage. The patches develop around the earliest attacked plant in a centrifugal manner. Infection of the tap root most commonly produced complete wilting whereas, infection starting and extending from one or two lateral roots often caused partial wilting.
Mode of Spread
Soil borne (primary spread) and Irrigation water and implements (Secondary spread)
Survival
The pathogen survives as soil borne chlamydospores in the soil and infected stubbles. The fungus survives upto 2.5 years in red soil and 3 years in black soil.
Epidemiology
The pathogen produces three types of asexual spores viz., macroconidia, microconidia, chlamydospores (resting spore)]. Soil temperature of 17-190 C favour the disease
Management
- Field sanitation
- Crop rotation with cotton or sorghum or cumbu
- Seed treatment with captan or thiram or T.viride @ 4 g/kg
- Application of green manures or compost 12.5 tons/ha
- Grow resistant varieties like AWR 74125, BDN 1, 2, BWR 370 and NP (WR) 15.
2. STEM BLIGHT/PHYTOPHTHORA BLIGHT – Phytophthora drechsleri f.sp. cajani
Symptoms
Dark-brown to black necrotic lesions encircling the stem can be seen at above soil level. The infected plants show upward rolling of leaflets with out chlorosis, withering of petioles. Longitudinal cuts in newly formed lesions show brown to black discolouration of the bark and cambium. Later, the older xylem tissue may become discoloured and the stem may break at lesion site.
Mode of Spread
Primary infection is through oospores and secondary spread is by zoospores from sporangia. Irrigation water and rain splash spreads the disease
Survival
The fungus survives as chlomydospores and oospores in soil and infected stubbles
Epidemiology
Cloudy weather, drizzling rain and a soil temperature of 17-190 C favour the disease
Management
- Seed treatment with metalaxyl @ 7 g/kg of seed
- Foliar spray with metalaxyl 500 g/ha
- Grow resistant varieties like ICPL 38, 4135, 8564, 8610, 8692.
3. STERILITY MOSAIC – Red gram sterility mosaic virus
The disease causes upto 95 per cent yield loss when the plants were infected early
Symptoms
The disease usually produces three types of symptoms. 1. Initially yellow patches intermingle with green colour of leaves. In severe case, leaves become smaller and cluster near tip because of shortened inter nodes. The infected plants do not produce flowers and pods. 2. The infected plants also produces ring spot with no sterility. It is characterized by green islands surrounded by a chlorotic halo on leaf lets, symptoms tend to disappear as the plants mature. 3. Mild mosaic with only partial sterility
Vector
Eriophyid mite – Aceria cajani transmit the disease
Epidemiology
Shade and humidity encourage mite multiplication and in turn the disease
Management
- Rogue out infected plants up to 40 DAS
- Spray monocrotophos 500 ml/ha to control vectors
- Grow resistant varieties like BSR-1, BSMR 1,2, pusa 15, 17 and pusa 18
