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Management of nematodes In vegetable cultivation

Management of nematodes In vegetable cultivation. Group members. K.G.S.Nirmanee . AG/07/08/76 G.R.D.Nirukshi AG/07/08/77 W.K.B.Perera AG/07/08/84 . Morphology of nematodes. Small, 300 to 1000 µm long by 15 to 35 µm wide. Not observable with naked eye, except cyst forms.

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Management of nematodes In vegetable cultivation

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  1. Management of nematodes In vegetable cultivation

  2. Group members K.G.S.Nirmanee. AG/07/08/76 G.R.D.Nirukshi AG/07/08/77 W.K.B.Perera AG/07/08/84

  3. Morphology of nematodes • Small, 300 to 1000 µm long by 15 to 35 µm wide. • Not observable with naked eye, except cyst forms. • smooth, unsegmentedbodies. • no appendages. • round and eel shaped worms.

  4. Parasitic nematodes, • Prominent feature is presence of stylet which helps to pierce plant tissues. • Have very slow movements. • Body features are very clear.

  5. Ecology • All plant parasitic nematodes live at least part of • their lives in the soil. • Nematodes occur in greatest abundance in the top • 15 to 30 cm of soil. • In agricultural soils, the distribution of nematodes • is usually irregular. • The greatest numbers of plant parasitic nematodes • is usually found in the root zone.

  6. Cont… • Migratory ectoparasitic nematodes may follow roots to depths of 150 cm or more. • The hatching of eggs may be stimulated by "hatching factors" secreted by roots. • Spread of nematodes is facilitated by water, wind, cultivation equipment, soil dispersal, mankind.

  7. Cont… • There are four general categories of nematodes • Sedentary endoparasites • Sedentary ectoparasites • Migratory endoparasites • Migratory ectoparasites

  8. The nematode remains outside of the plant and uses its stylet to feed from the cells of the plant roots are known as ectoparasitic nematodes.

  9. Migratory endoparasitic nematodes spend much of their time migrating through root tissues destructively feeding on plant cells.

  10. Root knot nematodes PATHOGEN: Meloidogyne species (~70 species)

  11. The most widespread and economically important species, • Meloidogynehapla • Meloidogyne incognita • Meloidogynearenaria • Meloidogynejavanica • Meloidogynegraminicola • Meloidogynechitiwoodi

  12. Symptoms • The most diagnostic root-knot nematode damage occurs below ground, numerous symptoms can also be observed above ground. Below ground symptoms: • Large galls or "knots" can form throughout the root system of infected plants. • Severe infections result in reduced yields on numerous crops and can also affect consumer acceptance of many plants, including vegetables.

  13. Cont… • The degree of root galling generally depends on three factors: nematode population density, Meloidogyne species, host plant species and even cultivar. • Meloidogynehapla (the northern root-knot nematode) produces galls less than half the size of those produced by M. incognita (the southern root-knot nematode) on the same plant hosts. • Each crop responds differently to root-knot nematode • infection.

  14. Carrots typically undergo severe forking with galling predominantly found on lateral roots.

  15. Root-knot nematode galls on lettuce are beadlike.

  16. On grasses and onions, galls are usually small and barely noticeable, often no more than slight swellings.

  17. Above ground symptoms: • Severely affected plants will often wilt readily. • only limited ability to absorb and transport water and nutrients to the rest of the plant. • Plants also may exhibit nutrient deficiency symptoms because of their reduced ability to absorb and transport nutrients from the soil. • Stunting is frequently observed on host crops grown in root-knot nematode-infested fields, and crop yields are reduced.

  18. Cont… • At high densities, root-knot nematodes can kill host plants, particularly if the high populations occur early in the growing season when plants have minimal root mass.

  19. Disease cycle

  20. Nematode secretions cause dramatic physiological changes in the parasitized cells, transforming them into giant-cells

  21. Disease Management Cultural Controls • Vegetable fields infested with M. hapla can potentially be planted to a nonhost crop such as corn. • So crop rotation is important. • Another cultural control strategy is the use of cover crops. • Cover crops such as marigolds actually produce chemicals that are toxic to nematodes. • Other techniques, including flooding and solarization of fields, have controlled nematodes.

  22. Cont… • Use of resistant varieties.  • Soil solarization using clear thins polythene cover for 3-6 weeks in summer has been also found very effective.  • Plough the main field twice in summer reduces nematode population and crop damage.

  23. Chemical Control • Very difficult to manage because they are soilborne pathogens with a wide host range. • Fumigants (such as 1,3-dichloropropene, methyl bromide and dazomet) are commonly applied as • pre-plant treatments. • The soil treatment of nursery beds with carbofuran. • Root dip treatment with systematic pesticides and hot water treatment of dormant infected planting material before transplanting in the main field is also recommended.

  24. Biological Control • There are many kinds of nematophagous (nematode-feeding) fungi, and most use mycelia traps or sticky spores to capture their nematode prey • Bacterial antagonists include species of Pasteuria. These bacteria attach to the cuticle of a juvenile nematode, produce penetration structures that enter the nematode, and slowly consume it.

  25. Root lesion nematodes Pratylenchusspp.: lesion nematodes • P. brachyurus • P. coffeae • P. neglectus • P. penetrans • P. scribneri • P. thornei • P. vulnus • P. zeae

  26. Pratylenchusspp. are migratory endoparasite of root. • The name of ‘root lesion nematode’ is derived from the discoloured patches (lesion) develop on roots. It has a very wide host range. • The above ground symptoms caused by the nematode are non-specific in nature. • The nematode usually infects in roots, rhizomes or tubers. • All the stages of this nematode are infective.

  27. Symptoms • Yellowing and stunting of tops may occur. • Loss of primary roots, severe pruning of roots, reduced size of blossom, shrinking of grains andreduced plant growth are associated with the nematode. • The most characteristic symptom, is production of lesions on roots, the extent may vary with nematode population density and host varieties. • The lesions appear as tiny, elongate water soaked spots which soon trub brown to almost black.

  28. Cont… • The wounds create a point of entry for other soil pathogens, such as the fungi Verticillium, Cylindrocarpon, Rhizoctonia, Colletotrichum, and possibly others. • Lesion nematode-infected plants typically have reduced root volumes and weights. • Feeding and migrationby these organisms kills cells. • Feeder roots are usuallydestroyed.

  29. Management Cultural Controls • Hot water treatment of bulbs, corns, tubers, and fleshy roots can control the dormant nematodes residing in them.  • Growing of Marigold,after main crop or between rows of main crop has been found quite effective management method.  • Summer ploughing of field reduces population density. 

  30. Chemical Control • Application of carbofuran at sowing reduces crop damage.

  31. Reniform nematodes Rotylenchulusreniformis: reniform nematode. • Reniform nematode is a very common, damaging pest of many plants in subtropical/tropical soils and sometimes occurs in protected temperate soil. • The adult female of reniform nematode (Rotylenchulusreniformis) is an obligate, sedentary semi-endoparasite of a wide range of host plants.

  32. The term 'reniform' refers to the kidney-shaped body of the mature female.

  33. Symptoms • The symptoms of damage to crops are non-specific on the above ground or even in the below ground parts necessitating a close observation to confirm their presence and damage. • Root necrosis resulting in severe root pruning and subsequent dwarfing of plants. • Lead to stunting, yellowing and wilting. • In some cases, the nematode may produce lesions, distortions or cracks on storage roots which reduce marketability.

  34. Cont… Storage root cracking associated with reniform nematodes • Infected plants generally grow less vigorously than healthy ones. • Infected plants have smaller root systems than healthy ones. • Infected roots appear dirty because of nematode egg sacs.

  35. Management Cultural Controls • Summer fallow and ploughing. • Clean cultivation. • Growing antagonistic/trap crops like african marigold, asparagus and crotalaria. • Grow resistant varieties. • Select fields with no previous record of nematode infestation. • Rotate crops with rice maize or groundnut to reduce nematode populations. • Solarize soil in summer to reduce nematode populations.

  36. Cont… Irrigation management:Irrigation between ploughings results in alternate drying and wetting which may stimulate exsheathment of young female of R. reniformis Crop husbandry:Good crop cultivation practices like field preparation, fertilizer application and moisture management can improve crop tolerance to nematodes

  37. Biological Control • A fungal egg parasite was found effective against the reniform nematode. • Host-plant resistance

  38. Chemical Control • Soil application of carbofuran gives good control • Seed treatment with 1-3% carbofuran by weight, application of non-edible seed cakes of neem.

  39. Cyst nematodes • Heterodera spp.: cyst nematodes • H. cruciferae • H. schachtii • H. carotae, • H. glycines, • H. trifolii,

  40. Cysts are the dead remains of female nematodes. • They are lemon-shaped and about the size of • a pinhead. • If cyst nematode-infected roots are examined • closely after gently removing the soil, these females can be seen with the naked eye. • They are white or yellow, depending on age. • Female cyst nematodes produce approximately 50 to • 100 eggs in a gelatinous matrix outside their bodies, and many more eggs remain within their bodies.

  41. Symptoms • Results in areas of stunted and yellow plants. • Cyst nematodeinfected plants often have reduced root systems. • Poor nodulation, pinhead size • White females on root tissue • Poor crop yield and poor crop quality.

  42. Left to right: broken cyst with eggs, cysts on roots, juveniles hatching from cysts

  43. Management Cultural Controls • Sites with histories of cyst nematode problems should be kept free from host plants for two or more years. • Crop rotation is the most effective tactic to reduce population densities of cyst nematodes. Chemical Control • Cyst nematodes are difficult to control with nematicides, though use of these materials can • result in declines in cyst nematode population densities.

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