Nematodes

Pant nematodes and their management

1. Management of Plant parasitic N ematodes

2. TOPICS : Introduction Methods Conclusion

3. INTRODUCTION OF NEMATODE MANAGEMENT : Nematodes are omnipresent T ransmitted through variety of methods. Irrigation water is the prime source infected composts soil. C ontrol methods is needed to raise crops economically.

4. METHODS : Regulatory methods Cultural methods Physical methods Chemical methods Biological methods

5. Regulatory Method: Quarantine / exclusion : This implies exclude the entry of a pest . Buy or grow transplants that are nematode-free. Use nematode-free soil or potting medium. Clean tools and equipment when changing areas or fields. Remove infected plant roots .

6. Cultural Control: Crop Rotation : keeping nematode population under check especially when there are distinct host preferences. Susceptible crops should be grown once in few years R otating them with non-host crops. Vegetables should not be grown in same field repeatedly. Keep weeds in check.

7. Fallowing and Ploughing : Keeping the land fallow and deep ploughing reduce nematodes e.g. root knots and others . Nematodes are sensitive to heat and drying action of the sun and the wind. So in hot and dry condition fallowing and ploughing are best remedy of nematodes control.

8. Use of Organic Amendments: Green manure compost, oil-cakes has been found to Reduced Nematodes. These encourage the growth of natural enemies and decomposition products Raising green crops also enhance development of some predacious nematodes in soil.

9. Use of Resistant and Tolerant Varieties: The most practical and economical methods of controlling nematodes . M ulti-resistant strains of plants to nematodes has been made T he main drawback sometimes is the development of resistant breaking nematodes which makes the process futile. Resistance has been mainly to root-knot nematode . Resistant and non resistant roots:

10. Flooding : Flooding can be adopted where there is an enormous availability of water. Under submerged conditions , anaerobic condition, kills the nematodes by asphyxiation. Chemicals lethal to nematodes such as hydrogen sulphide and ammonia are released in flooded condition which kills the nematodes.

11. Adjust planting time: Nematode life cycle depends on the climatic factors . Adjusting the time of planting helps to avoid nematode damage. In some cases crops may be planed in winter when soil temperature is low ad at that time the nematodes cannot be active at low temperature. Early potatoes and sugar beets grow in soil during cold season and escapes cyst nematode damage.

12. Antagonistic crops: Certain crops like mustard, marigold and neem have chemicals or alkaloids as root exudates which repel or suppress the plant parasitic nematodes In marigold plants : α terthinyl and bithinyl compounds In mustard : allyl isothiocyanate P angola grass: Pryrocaterchol Such enemy plants can be grown along with main crop or included in crop rotation.

13. Trap cropping : Two crops are grown in the field, out of which one crops is highly susceptible to the nematode. The nematode attacks the susceptible crop. By careful planning, the susceptible crop grown first and then removed and burnt. Thus the main crop escapes from the nematode damage. Cowpea is highly susceptible crop can be grown first and then removed and burnt. Cowpea is highly susceptible to root knot nematode and the crop can be destroyed before the nematodes mature.

14. Physical : Heat treatment of soil : This is a general practice for soil sterilization against all organisms harmful or beneficial. Nurseries use autoclaved soil [ 30 psi for 30 minutes] for potting.  In greenhouses steam is released through perforated pipes running through the soil. Dry heating of soil by burning off the standing crop waste is also practiced.

15. Hot water treatment of planting material : It is mainly used for transplanted crops, bulbs, rhizomes, root stock and tubers. Usually dormant bulbs of ornamental plants and root stocks of citrus are given this treatment. Hot water treatment of rice seed is a very effective method to control white tip nematode which is transmitted through seed.

16. Solarization : This method involves covering moist soil with polythene film during period of intense sunlight and heat. This capture energy from sun thus bringing change in physical ,biological and chemical changes in soil. The soil temperature increased is lethal to many of soil borne nematodes. It increase soil fertility by increasing availability of nitrogen and other essential nutrients. This method of nematode management is very useful where heat from sun rays is sufficient. It only reduce nematode population , but not enough to finish all nematodes .

17. Dry heat: Dry heat also reduce nematodes population. Nematodes egg and their juvenile stages are usually killed if they are exposed to dry heat. Use of oils : Spraying 15% water soluble oil reduces infestation by nematodes. Many of oils also used also reduce the counts of eco-parasitic nematodes. By this spraying nematodes movement sis restricted and quantity becomes low

18. Exposure to direct sunlight: Spread infested layer of soil in thin layers up to few cm on soil. Exposed layer to sunlight for 10 days in summer to eliminate nematodes that are present in soil layer . This practice is useful for preparing soil mixtures for ornamentals and nursery beds. Irradiation : It is an effective means to kill nematodes though it is non-feasible and non-practical. UV rays used are lethal to nematodes. Many other radioactive rays are used in this management technique .

19. Osmotic pressure : Addition of dextrose or sucrose to nematode infested soil is detrimental to nematodes. This reduce or restrict nematodes production or population. Although this method is non-economical and non-practical. Floatation of seed : This is done in order for removal of nematode galls from seed material and floatation. Flooding and floating of seeds are done to control nematodes population. Seed also cleaned by mechanical cleaners to kill gall nematodes.

20. Chemical control Fumigants : These are first to identify as control in plant parasitic nematodes. They may be applied to the soils as liquids, emulsions or granules but the active ingredient spreads in the soil in the form of a gas. These are applied as pre-plant treatments mostly. It is essential that the soil be treated is well prepared to a seed bed condition. Soil moisture is moderate , uniform and the soil temperatures should between 15 to 30 o C at the time of application.

21. Commonly used fumigants : DD EBD MBr DBCP CS2

22. APPLICATION : DD and EBD are highly phytotoxic and are applied 3 to 4 weeks before planting. DBCP can however can be used with irrigation water around the roots of plants as recommended. DBCP mostly used as pre –planting . It is mostly used on perennials (citrus root nematode).

23. Non-fumigants/nematicides: These are applied to living plants parts and as pre –plant treatments to annual crop. T hese are applied in granular form. These are applied during or shortly after planting to wet soils. It is important to have their application along irrigation water in order to have proper dispersal through out soil surface. Some of nematocidal are insecticidal thus providing early insect control. These are classified as carbamates and organo -phosphates . These compounds control many soil and foliar feeding nematodes .

24. non fumigants fumigants Less phytotoxic Applied during planting and post planting Greater residual activity Effective at lower dosages Control both soil and foliar nematodes Somehow phototoxic Applied before planting usually Less residual activity Not effective at lower dosages Control only soil nematodes

25. Nematicides : Used against : Dichlorofenthion First used for management of root knot nematode on turf and ornamentals. Thionozin Used against as sting nematodes in maize and root knot in vegetables. (1957) parathion Used against A.fragarie (1948) Dazomet Used against root knot and lesion nematodes (1957) phorate Used against many nematodes as stunt, root lesion etc. fensulphothion Used against turf nematodes phenamiphos Used against root knot and bare root dip in citrus. Commonly used nematodes :

26. Nematicides Used against : Ethoprop Used against root knot nematodes affecting tobacco ,tomato and also against other. Aldicrab Used against tobacco cyst nematode carbofuran Used against many nematodes as heterodera, Globodera. oxyamyl Used against many nematodes.

27. Experimental compounds : Some compounds also posses nematicidal activity for nematodes control. They are : Amino acids Antibiotics (KT-199) Lavamisol Aldoxycrab Formaldehyde urea Sodium azide Avermectins Binapacryl phenols

28. Biological control.

29. Characteristics : Host specific Parasitism is always lethal Easily manipulated in laboratory Can be mass produced Easily disseminated with standard equipment Potential for establishment & recycling Provides control for extended period Not harmful to environment Shelf-life of at least one year No hyperparasites Compatibility with others

30. Predators of nematodes: Important predators of plant parasitic nematodes are mites , insects ,enchytrieds and migratory nematodes.

31. Parasite of nematodes: Bacteria and some fungi are major parasites of plant parasitic nematodes. Several fungi are isolated that parasitizes the nematode. Fungi act as opportunistic . No virus still documented to harm nematodes.

32. Use of nematophagus fungi It is parasite . These forms trap usually. Several species of soil-dwelling fungi produce traps to ensnare nematodes before they infect them.  Traps come in many forms: adhesive hyphae, networks, knobs, rings, and constricting rings.  Some trapping fungi can proliferate in soil in the absence of nematodes while others are more dependent on nematodes as a nutrient source for growth . As Arthrobotrys oligospora parasitic fungi

33. ENDOPARASITic ENDOZOIC FUNGI These fungi produce either simple or flagellate adhesive spores which upon contacting a nematode quickly and firmly attached to its cuticle. It then germinates and enter the nematode body through germ tube . Simple spore are ingested by nematode, reach the esophagus / buccal cavity where they germinate e.g.. Harposporium anguillulae While sticky spores stick to the nematode body & germinate and penetrate directly through the nematode cuticle, produce infective hyphae e.g. Meria coniospora & Nematoctonus bisporus . Nematodes get restricted nutrients and ultimately weakens .

34. Parasitic fungus ( zoosporic ) Zoospores are motile spores that are propelled by one or two flagella.   When  zoospores locate a host, they attach to the nematode cuticle, often near a body opening (mouth, anus, vulva), shed their flagellum, and become sedentary (i.e., encyst).  The encysted zoospores infect the nematode cuticle by forming a penetration tube that enters through an orifice or directly penetrates the nematode cuticle.

35. Continue… When the resources within the infected nematode are exhausted, the hyphae differentiate to form sporangia.  Zoospores are produced within the sporangia and enter the soil via an exit or discharge tube which is formed when the spores are mature.   Zoospore-forming fungi are believed to be opportunistic parasites of vermiform nematodes, attacking or colonizing weakened or dead nematodes. As Catenaria anguillulae

36. Egg parasitic fungus : There are a large number of fungi that can parasitize nematode eggs, and the sedentary juveniles and females of cyst and root-knot nematodes.  These fungi categorized in two groups. One is obligate parasitic fungi those that can grow only in nematodes. Second is facultative parasitic fungi that can grow to some extent in nematodes as well as on organic matter in the soil.

37. Toxic chemicals released: The filamentous fungi have been widely studied for their effectiveness in controlling nematodes. The mechanisms involved in this is direct through antibiosis and parasitism . Trichoderma grows around the target and releases toxic compounds and different lytic enzymes mainly chitinases , glucanases and proteases . These proteins facilitate Trichoderma penetration into the nematode and the utilization of the nematode components for nutrition . The role of these lytic enzymes has been proved in nematode control.

38. Bacteria: Some of them are endospore-forming actinomycetes that are parasites of nematodes.   Some rhizosphere-inhabiting bacteria are antagonistic to plant-parasitic nematodes.  S ome bacteria inhibit nematode egg hatch and/or penetration of roots.  Mechanism involved Production of antibiotics that kill nematode eggs. Degradation of the root exudates that the nematode relies on for host location and to stimulate egg hatch.

39. Mites : The soil mite Lasioseius subteraneus Mesostigmata Ascidae are an aggressive predator of nematodes that colonizes greenhouse cultures of root-knot nematodes.  This mite has a generation time of less than 1 week at 28 ºC and can lay up to 18 eggs per day when feeding on nematodes and kill them .

40. Management Summary : No single practice will control nematodes, so two or more control methods must be used.