Diseases Of Blackgram And Greengram

By TamilNadu Agricultural University on 08 Nov 2016 | read

1. Root rot

Causal organism : Rhizoctonia bataticola

Symptoms: Affected plant exhibits drooping and drying of leaves and branches. The basal portion of stem turns brown and the bark of the roots become shredded. Large number of spherical to irregular black sclerotiacan be seen in shredded tissues.

Favourable conditions :Day temperature of 30˚C; Prolonged dry season followed by irrigation.

2. Powdery mildew

Causal organism : Erysiphe polygoni

Symptoms: On the upper surface of leaf, white powdery growth of the fungus is seen. More often, the entire surface is covered. The color of the growth later turns grey and the leaves become brown. The disease becomes severe during flowering and maturity stages. The white growth consists of the external mycelium, conidiophores and conidia.

Favorable Conditions :Warm humid weather. The disease is severe generally during late kharif and rabi seasons.

3. Leaf spot

Causal organism : Cercospora canescens

Symptoms:Small circular to irregular reddish spots are observed on thesurface of leaves. The center later turns grey and defoliation occurs insevere cases. Large number of conidiophores and conidia are formed inthe center. Lesions can also be seen on petioles and stem.

Favorable Conditions : Humid weather and dense plant population

4. Rust

Causal organism : Uromyces phaseoli typical

Symptoms: On the lower surface of leaf reddish brown pustules are seen in abundance, representing the uredosori of the fungus. Affectedleaves turn yellow. The uredospores are brown, echinulate and single celled. Teliospores are elliptical and papillate. The fungus is anautoecious, macrocyclic rust.

Favourable Conditions :Cloudy humid weather, temperature of 21-26˚C .Nights with heavy dews.

5. Yellow mosaic

Causal organism : Mungbean yellow mosaic virus (MYMV)

Symptoms: The initial infection is observed as small irregular, yellow patches on leaves. These patches enlarge in size and cover the entire lamina. The whole leaf later completely turns yellow. Pods become yellow, small and distorted.

Favorable condition: Transmitted by white fly, Bemisia tabaci under favorable conditions. Disease spreads by feeding of plants byviruliferous whiteflies. Summer sown crops are highly susceptible. Weed hosts viz., Croton sparsiflorus, Acalypha indica, Eclipta alba and other legume hosts serve as reservoir for inoculum.

6. Disease : Leaf crinkle

Causal organism : Urdbean leaf crinkle virus (ULCV)

Symptoms: Initial symptoms appear on young leaves. Affected leaves are puckered and curled. The plants get stunted and appear bushy.Petioles and internodes are shortened. The inflorescence is deformed.Flowers seldom open.

Favourable condition:Presence of weed hosts like Aristolochia bracteata and Digera arvensis. Kharif season crop and continuous cropping of other legumes serve as source of inoculum. The virus is seed-borne and primary infection occurs through infected seeds. Perhaps white fly, Bemisia tabaci helps in the secondary spread. The virus is also sap transmissible.

Disease management:

1.Seed treatment

a.Talc formulation of T. viride @ 4g or P. fluorescens @ 10 g/kg seed(or) Carbendazim 2 g/kg or Thiram @ 4 g/kg

b.Root rot-stem fly complexSeed treatment with Beauveria bassiana + Pseudomonas fluorescens @5 g each/kg of seed