Diseases of Groundnut (PDF)

Diseases of groundnut Diseases of crop plants and their management (2+1)  Tikka Disease Early leaf spot Causal agent : Cercospora arachidicola – Anamorph Mycosphaerella arachidis – Teleomorph Late leaf spot Causal agent : Phaeoisariopsis personata - Anamorph...

Diseases of groundnut Diseases of crop plants and their management (2+1)  Tikka Disease Early leaf spot Causal agent : Cercospora arachidicola – Anamorph Mycosphaerella arachidis – Teleomorph Late leaf spot Causal agent : Phaeoisariopsis personata - Anamorph Mycosphaerella berkeleyii - Teleomorph  Character Early leaf spot Late leaf spot Sl.no. 1. Stage of occurrence Early infection 3-4 weeks after Usually late infection, 5-7 weeks sowing after sowing 2. Shape of spot Circular to irregular Usually circular Sporulation and 3. Upper surface, scattered Lower surface, concentric rings arrangement 4. Colour of spot on upper Light brown to black and has Dark brown to black, yellow halo surface conspicuous yellow halo absent or not conspicuous 5. Colour of spot on the Brown Black lower surface 6. Causal organism Cercospora arachidicola Phaeoisariopsis personata Anamorph: Teleomorph Mycosphaerella arachidis M.berkeleyii  Nature of mycelial Initially intercellular but later Intercellular 7. growth intracellular 8. Presence of haustoria Absent Branched haustoria present In fascicles (5 or 7) Dense fascicles Conidiophores Golden brown but darker at base. 9. 20-50x3-5μm Pale olivaceous brown 10- 100 x 3-6.5μm Conidia Lightbrown/ olivaceous Pale yellow Obclavate and Colour Shape curved Cylindrical/obclavate/straight/ 10. Slightly curve 11. Presence of hilum Present Conspicuous 12. Perithecia Larger in size(84-140 x 70-112μm) Smaller (47.0-84 x 44.0-74.0μm)  Management Crop rotation of cereal- cereal- groundnut and burying crop residues by deep ploughing help in reducing the inoculum. Multiple application of a fungicide such as benomyl, chlorothalonil, copper hydroxide, mancozeb or sulphur fungicides helps in controlling early and late leaf spots. However, three sprays of 0.2% chlorothalonil / 0.1% carbendazim at fortnightly intervals starting from 40 days after germination up to 90 days provide effective control. Growing resistant cultivars like ICGV 87160 or ICGV 86590  Groundnut Rust Causal agent : Puccinia arachidis Symptom Orange pustules (uredinia) containing reddish brown uredospores on the lower leaves surface. On the corresponding upper surface of leaves, chlorotic spots with necrotic brown areas in the centre. In severe cases, drying of leaves Pathogen Uredial and telial stages are produced. Uredospores single celled, ovoid to round and pedicellate. Teliospores dark brown and two celled Management Spraying fungicide like Bordeaux mixture 1%, chlorothalonil 0.2%. Spraying should be started from 30 days after germination till 15 days before harvest at regular intervals of 10-15 days. Spraying tridemorph (Calixin) 0.1% gives more effective control of the rust. Use of resistant varieties like ICGV 87160 or ICGV 86590 Efforts are also made to develop biological control using hyperparasites like Verticillium lecani, Darluca filum etc.  Groundnut stem and pod rot Causal agent Sclerotium rolfsii Symptoms Brownish lesion on the base of plant Chlorosis and wilting of foliage pegs will have retarded pod development appearance of white mycelial growth and brown sclerotial body on the collar region. Management Use cereal-cereal-ground nut crop rotation and seed treatment with thiram. Avoid drought at pod formation and maturity. Grow varieties tolerant to stem and pod rots like ICGV 87157, ICGV 86590 etc.  Groundnut Yellow Mold Causal agent : Aspergillus flavus Symptoms Yellow mold on groundnut cotyledons after the emergence of seedlings. Necrotic spots become covered with masses of yellow-green spore heads of the fungi. Yellow-green Aspergillus colonies develop on over mature and damaged seeds and pods (Yellow mold phase). Seedlings lack a secondary root system (Afla root ). Management Harvest at proper maturity. Dry the groundnut pods to 6-8% moisture content immediately after harvesting and discard the infected pods and seeds. Prevent drought stress, and also prevent water logging (40-80% of field capacity) at late stage of growth.  Crown/Collar rot Causal agent : Aspergillus niger Symptoms Pre emergence phase : Seeds are covered with sooty black mold growth, resulting in rotting of seeds and seedlings before emergence. Post emergence phase : Circular light brown lesion appear on the cotyledons leading to death of seedlings. Dark brown lesion on the collar region, expands and result in shredding Management Same as groundnut yellow mold. Bud necrosis Disease Causal agent : groundnut bud necrosis virus (GBNV) and tomato spotted wilt virus (TSWV) Symptoms Appearance concentric rings or chlorotic spots on young leaflets. Necrosis of terminal bud Stunting, axillary shoot proliferations may be restricted to the terminal portion. Management Use resistant/tolerant cultivars: ICGV 44, ICGV 87141, ICGV 87187, ICGV 87119, ICGV 87121, ICGV 87160, ICGV 87157 or ICGV 86590. Control of vectors with systemic insecticides like Actara @ 2ml/10L Intercropping of groundnut with cereals, i.e., pearl millet will restrict spread of the virus.