Diseases of Beans

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1. Diseases of Bean HPP 5311 Diseases of vegetables, ornamentals and spice crops.

2. Anthracnose The disease is more severe in temperate and subtropical mountaneous regions of the world with cool and wet climate. Colletotrichum lindemuthianum

3. Symptoms All the above ground parts are affected at any stage of crop growth. However, the characteristic symptoms appear on pods. On cotyledons spots are sunken dark brown or black with pink spore mass. Seedling infection results in collapse of seedling. Spots on leaves appear on lower side and are black. Later these may also appear on upper surface. When the infection is severe, the affected plants wither off.

4. Black, sunken, circular spots of varying sizes appear on pods with bright red, yellow or orange margins. The centre of these spots later turns grey or pink due to sporulation of the pathogen. The border of these spots appear raised.

5. Pathogen The mycelium is branched, septate and hyaline at first becoming dark with age. The acervulus contains a layer of 3 to 50 conidiophores depending on the size of lesion. Conidia are hyaline, cylindrical having rounded ends or somewhat pointed at one end and often bear a clear vacuole like body near the centre. The teliomorph of the pathogen has been identified as Glomerella cingulata ( Ston .) Splaud & Schrenk

6. Survival and spread

7. Management Follow 2-3 years of crop rotation with non-leguminous crops. Use disease free seed and treat them with carbendazim or benomyl (0.2%). Resistant cutivars / lines like KRC 1, KRC 17, EC 42960 and EC 57080 have been identified as resistant to this pathogen. In field, the spread of the disease can be limited by application of fungicides like mancozeb (0.25%) or combination of mancozeb (0.25%) and carbendazim (0.05%) or tricyclazole (0.03%) and repeat at 10 -14 days interval.

8. Rust Uromyces fabae

9. Symptoms The symptoms mostly appear on leaves, though often they are found on petiole and stem of some hosts. The rust pustules appear on either sides but more common on lower surface. The Uredosori are minute, roundish, slightly raised and reddish brown coloured. These contain rust spores and appear in groups.

10. Later in the season with the formation of teliospores, the sori turn dark brown or black. Diseased leaves may wither or fall off under severe infection

11. Pathogen The urediniospores are brownish, globoid or ellipsoid, one celled and echinulate. Spore wall is golden brown 1-1.5 μm thick having two equatorial pores. Teliospores are dark brown coloured, elliptical and ovate, pedicillate, smooth walled, single celled with warty papillae at the top.

12. Disease cycle and epidemiology P.I: Survives through teliospores in cooler regions and on collateral hosts S.I: Wind borne Uredospores Host range: French beans, green gram, black gram and cowpea. Areas having high humidity and temperature upto 24⁰C are most suitable for disease development. Urediniospores germinate optimally at 15-24⁰C while for teliospores germination, 10-15⁰C is optimum.

13. Management Collect and destroy the infected plant debris. Follow long crop rotations. With the initiation of the disease, spray the crop with mancozeb (0.25%) or hexaconazole (0.1%) or difenoconazole (0.05%) or combination of mancozeb (0.25%) and hexaconazole (0.05%) and repeat at 10 days interval.

14. Yellow mosaic Bean Yellow Mosaic Virus, Mungbean yellow virus or Phaseolus virus-2 ( ss DNA virus)

15. Symptoms Bright yellow patches appear on leaves. Yellow areas alternate with dark green areas of the leaf blade. Younger leaves show more severe mottling and chlorosis. Leaves completely turn yellow and gradually becomes necrotic Plants are stunted and flower and pod set is reduced Pod formation is reduced and if produced, they are deformed having shrivelled and undersized seeds

16. Survival and spread P.I: Collateral hosts S.I: Whitefly , Bemisia tabaci Not transmitted by sap, seed and pollen Host range : French bean, Soybean, Red gram, Xanthium strumarum , Eclipta alba, etc.

17. Management Remove collateral hosts and destroy Use resistant varieties Spray [email protected]% for vector control