Damping off, collar rot/gummosis of citrus and Papaya and root rot of jute

This was presented by one of the group of students to our Asst. professors Mr. and Mrs. Poudel (Pathology) in 2017. By B.Sc.Ag Paklihawa IAAS campus, Full phase 6th batch

1. PRESENTATION ON Damping off Stem and root rot of jute Stem, foot ,collar rot of papaya Collar rot /gummosis/ brown rot of citrus

2. Damping off soil borne fungal disease Results in rapid death and collapse of very young seedlings Hosts : Tomato, Brinjal , Chilly, Tobacco

3. Etiology: Pythium root rot: Pythium sps Cause damping off of seedlings and root rot of cuttings. Infection occurs in cool, wet, poorly drained soils and by overwintering. When severe, the flower portion of the stem becomes slimy and black circular patches appears. Phytopthora root rot: Phytopthora sps Usually associated with root rots of established plants. Enter the root tips and cause water soaked brown to black rot similar to Pythium .

4. Rhizoctoinia root rot: Rhizoctinia solani Infection occurs in warm to hot temperatures and moderate moisture levels. Black root rot: Thielaviopsis bacicola Usually affects lateral roots where they just emerge from taproot. Doesn’t affect in strong acid soil 4.5 to 5.5. Fungi survives for 10 years or more in soil. White mould( sclerotinia rot): Sclerotinia rolfsii , Macrophomina phaseoli Bortytis (grey mould): Bortrytis , Fusarium

5. Symptoms: cell wall of rapidly growing seedlings is generally thin and tissue is particularly vulnerable The pathogen causes invasion rapid killing rot of cells and collapse of the tissue sudden toppling over of the seedlings.

6. Pre-emergence damping off: Young seedlings die before they reach soil surface when hypocotyls has just emerged. Radical and plumule are destroyed as soon as they come out of the seed coat.

7. Post emergence damping off: Seedling emerges and grows to a height of an inch, then wilts and dies. Roots-brown or black lesions, water soaked lesions. Browning and shriveling of stem tissues at soil level on the collar region.

8. Post emergence damping off: Foliage –yellow and premature falling starting with older leaves. Root rot include stunting and wilting. Finally toppling down and ultimate death of the seedlings.

9. Disease cycle and epidemiology: Pythium - Saprophyte on plant debris or humus in the soil and becomes parasitic when the proper host and growing conditions are present. For host infection by direct penetration, soil temperature (20 to28) ℃. Dessimination of innoculum = as oospores in plant debris and mycelium in the soil with the help of water, rain splashes. Oospores -formed by the fertilization of oogonium and antheredium , germinate by the formation of germ tube and penetrate the cell wall of hypocotyl and incite primary infection. Sporangium upon germination give rise to zoospores that are biflagellate and produce germ tube thus inciting secondary infection. Source of contamination =soil or compost used in the seedbeds.  

10. Conditions: Excessive soil moisture. Low soil temperature before germination (below 20℃or 68℉). High soil temperature after emergence (25℃or 77℉). Overcrowded flats or seedbeds.

11.   Management: Prevent overcrowding of seedlings Reduce moisture level. Seed bed soil preparation: use sterilized soil, make alkaline free soil. Soil treatment: 2.5% formalin solution fortnight before sowing.

12. Management: Seed treatment: Hot water treatment, fungicidal trt-2gm/ ltre captan , thiram and carbendazium to avoid pre-emergence damping off.

13. Stem and root rot of jute Occurs at all stages of jute. Etiology : Macrophomina phaseoli ( pycnidial stage), Rhizoctonia solani ( sclerotial stage) Hosts : Jute, sesame, cowpea, linseed, corn, potato

14. Symptoms : In young seedlings, about 1inch high. Appearance of blackish brown to black lesions on the hypocotyls and cotyledons . Under wet conditions, younger seedlings damp off.

15. Symptoms : After seedling has reached three-leaf stage , necrotic lesions appear at the apex and along the margin of the leaves ultimately covering the entire leaf. Lesions on the stems usually occur at nodes as blackish brown depressions which may coalesce and gradually girdle the stem causing rot. Wilting of the affected plants and premature leaf fall. Infection spreads to root and kills the plant. In severe form, capsules and even seeds are also attacked and pycnidia and sclerotia are formed.

16. blackish brown Lesions on the stems -

17. Disease cycle and epidemiology: Fungus- facultative parasite, can survive saprophytically on dead organic matter in soil. Primary innoculum - infected seed and soil in the form of pycnidia and sclerotia . Mycelium - found in all parts of stem, especially in epidermis and cortex. Pycnidia - found in epidermis while sclerotia - in phloem and xylem. CONDITIONS: Prolonged warm and humid conditions.

18. Management : Proper spacing 30cm×7cm. Crop rotation jute with paddy. Spraying 0.2%lime sulphur reduces leaf infection. Foliar application with Bavistin 2gm/ ltre . Root rot can be effectively reduced by using Brassicol . Collateral hosts as linseed, sesamum and cowpea shouldn’t be grown in jute fields. Weed Cyperus distants should be eradicated to reduce the source of innoculum .

19. Stem,Foot,Collar Rot 0f Papaya Etiology : Pythium aphanidermatum

20. Symptoms: Water soaked lesions on the stem near ground level. Softening of the tissue . Patches enlarge rapidly and girdle the stem, causing rotting of tissues, which then turns dark brown or black. If disease attack is mild, only one side of the stem rots. Rotting proceeds to roots and plant remains stunted Fruit- shriveled and drop. Roots -deteriorate and get destroyed

21. Leaves-yellow, wilt and droop acropetally .

22. Disease cycle and epidemiology : Primary innoculum - oospore . Secondary infection- via biflagellate zoospore developed by sporangia.

23. Condition: High relative humidity and excessive rain. High temperature of 30℃. Excessive amount of nitrogenous fertilizers and manures. Attacks plants of one to three years of age.

24. Management : Seed treatment – Captan@4gm/kg. Soil drenching with Calixin (0.1%). Drench the base of the stem with Bordeaux mixture @2g/ ltre or captan@2gm/ ltre or metalaxyl@1gm/ ltre .

25. COLLAR ROT OF CITRUS Hosts: most scion cultivars of citrus sps . Etiology : Phytopthora palmivora , P. citrophthora , P.hibernalis , P. parasitica , P. nicotianae var. parasitica

26. Occurs when sap oozes from wounds as a reaction to outside stimuli such as adverse weather conditions, infections, insect problems, or mechanical damage.

27. Symptoms: Yellowing and premature falling of leaves cracking of bark and profuse gumming on the surface. oozing or yellowish or reddish brown gum in large quantities from affected , cracked parts giving tree a bleeding appearance the bark becomes completely rotten and the tree dries owing to girdling effect.

28. symptoms Prior to death, the plant usually blossoms heavily and dies before the fruits mature. In such cases, the disease is called foot rot or collar-rot. Stringy appearance of root system Light brown, leathery and non sunken rind compared to adjacent rind

29. Formation of patches of gummy substance on the surface of plants, particularly fruit trees.

30. Brown rot of citrus

31.   Disease cycle and epidemiology Pathogen survives as oospores and chlamydospores in soil or in old cankers. Under favourable condition, it produces motile zoospores that are infective agents. When zoospores contact roots, they encyst , germinate and enter the root tip resulting in rot of the entire rootlets. Foot rot or gummosis occurs when zoospores splash onto a wound or bark crack around the base of the trunk.

32. Conditions: Heavy soil with impeded drainage. High soil moisture. 5.4 to 7.5 temperature=24℃ High nutritional status Deep planting.

33. Management: Selection of proper site with adequate drainage, use of resistant varieties, avoiding contact of water with the trunk by adopting ring method of irrigation. Scrapping the diseased portion with a sharp knife and disinfecting the cut surface with Mercuric chloride (0.1%) or Potassium permanganate solution (1%). Spraying with Bordeaux mixture (5:5:50). Metalaxyl and fosetyl Al as systemic fungicides

34. THANK YOU!!!