Diseases of Brinjal

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1. DISEASES OF BRINJAL HPP 5311 3(2+1) Diseases of vegetables, ornamental and spice crops

2. Little leaf Pathogen Phytoplasma The disease is caused by Phytoplasma having ovoid to spherical body which is concentrated in the phloem sieve tubes.

3. Symptoms Small or little leaves. The petioles are so short that the leaves appear to be sticking to the stem. Affected plants have narrow, soft, smooth and yellow shorter leaves. Newly formed leaves are much shorter. Internodes of the stem are also shortened. Axillary buds get enlarged but their petioles and leaves also remain shortened giving the plant a bushy appearance.

4. Mostly there is no flowering but if flowers are formed they remain green. Fruiting is rare, if any fruit is formed, it becomes hard, tough and fails to mature. Young fruit turns necrotic, get mummified and cling to the plant

5. Spread The pathogen perenneates in weed hosts. Jassid - Hishimonas phycitis . The disease is also transmitted by Emposca devastans , however, it is a less efficient vector. The varieties pusa purple long and selection T are highly susceptible. Collateral hosts: Datura fastuosa, D. stramonium, Vinca rosea, Argemone mexicana, chilli, tomato and tobacco.

6. Disease cycle

7. Management Tolerant variety: Pusa Purple Round, Pusa purple cluster and Arka sheel Destruction of affected plants. Eradication of solanaceous weed hosts. Spray methyl demeton, 2 ml/l or soil application of phorate granules. Seed dip in tetracycline (10-50 ppm).

8. Bacterial wilt Pathogen: Ralstonia solanacearum The bacterium is Gram negative motile, rod, having rounded ends with 1-4 polar flagella. Race 1 of R. solanacearum affects solanaceous plants such as tomato, egg plant and many other non-solanaceous plants also.

9. Symptoms Sudden wilting and death of infected plants is the characteristic symptom. The petiole of older leaves droop down and the leaves show epinasty symptoms accompanied by yellowing and stunting of whole plant. Typical browning of vascular tissues of roots and stems can be seen. From cross sections of infected plants whitish bacterial exudate comes out.

10. Mode of survival and spread The bacterium is both soil and seed borne in nature and overwinters in infected plant parts, in wild host plants and weeds. Spread through irrigation water or infested soil and agricultural implements.

11. Disease cycle

12. Favourable conditions Relatively high soil moisture and soil temperature favour the disease development. Management Grow resistant varieties like Pant Samrat , Arka Nidhi, Arkas Kashav , Arka Neelakantha , Surya and BB 1, 44 & 49. Crop rotation with non solanaceous hosts Green manuring with Brassica species ( Biofumigation ) Soil solarization with a transparent polyethylene sheet (125 μm thick) for 8-10 weeks during March-June Biological control with Pseudomonas fluorescens , P. glumae , P. cepacia , Bacillus sp. & Erwinia sp.

13. Nursery application: Treat the seeds with talc based formulation of antagonistic Pseudomonas f1uorescens (1Og/1OOg of seeds) and soil application of antagonistic P. f1uorescens (50g mixed with one kg of soil and incorporated in the nursery bed). Main field treatment: Dip the seedlings in the antagonistic P. f1uorescens/ B. subtilis (@ 259 talc formulation per litre of water) solution for 20-30 minutes just before transplanting. The left-over solution should be drenched around the root zones (50ml/plant).

14. Phomopsis fruit rot or blight The disease is severe in tropical and sub-tropical areas of the world. In India, it was reported in 1935 in Gujarat. The pathogen attacks foliage and fruits, but the latter phase is more destructive. Pathogen: The mycelium of the pathogen is septate and hyaline becoming dark with age. Pycnidia are submerged and later becoming erumpent with a prominent ostiole. Conidia are produced on simple to branched conidiophores and are of 2 types: Alpha conidia, which are sub cylindrical and beta conidia, which are filiform and curved. Role of beta-conidia in the epidemiology of the disease is not very clear. The perfect stage produces perithecia in which asci with 8 hyaline, bicelled, ellipsoid-fusoid ascospores are produced which are usually constricted at septum.

15. Symptoms The plants are attacked at all stages of growth, producing damping-off symptoms in nurseries and collar rot on young plants. On leaves, circular to irregular, clearly defined grayish brown spots having light centers appear. The diseased leaves become yellowish in colour and may drop off. Several black pycnidia can be seen on older spots. The lesions on stem are dark brown, round to oval and have grayish centers where pycnidia develop. At the base of the stem, the fungus causes characteristic constrictions leading to canker development and toppling of plants.

16. On fruits, small pale sunken spots appear which on enlargement cover entire fruit surface. These spots become watery leading to soft rot phase of the disease. A large number of dot like pycnidia also develop on such spots. The infection of fruit through calyx leads to development of dry rot and fruits appear black and mummified.

17. Mode of survival and spread

18. The pathogen is seed borne and also survives in plant debris both as mycelium and pycnidia. Seed infections directly lead to diseased seedlings. The pycnidiospores are disseminated through rain splashes, irrigation water, agricultural implements and insects. OR P.I: Pathogen is seed borne and also survives in plant debris as mycelium and pycnidia. S.I: Conidia dispersed through rain splashes, irrigation water, agricultural tools and insects.

19. Favourable conditions High relative humidity coupled with higher temperatures favour disease development. Maximum disease development takes place at about 26⁰C under wet weather conditions with 55% R.H .

20. Management Removal and destruction of diseased crop debris. Practicing crop rotation and summer ploughings helps in reducing initial inoculum. Use of disease free seed Hot water treatment of seed at 50⁰C for 30 minutes. Seed treatment with thiophanate methyl at 1g/kg seed. Spray twice with thiophanate methyl or [email protected]% at 20 days interval.

21. Cercospora leaf spot Several leaf spot diseases affect this crop but the leaf spots caused by Cercospora species are important which under high humidity conditions cause considerable yield losses.

22. Symptoms Cercospora melongenae The symptoms of the disease appear as circular to irregular leaf spots, which are usually large and brown to grayish brown in colour. Later spots coalesce together and affected leaves fall down prematurely and sometimes fruits may rot.

23. Disease cycle The fungus survives from one season to another in infected plant debris in soil and also in infected seeds wherever fruit rot occurs. Warm days and cool nights are ideal for the infection. The disease is favoured by high humidity and heavy persistent dews. Water droplets must be present for spore germination and germ-tube penetration. Moist wind, irrigation water and insects help in local transmission of the pathogen.

24. Management Cultural practices like destruction of crop debris, crop rotation, use of disease free seeds and wider plant spacing should be followed to reduce the primary inoculum of the pathogen in field. With the initiation of the disease spray the crop with zineb (0.25%), carbendazim (0.1%) or thiophanate methyl (0.1%) and repeat at 10 to 14 days interval.