Principles and Practices of Nematode Control

1. Principles and Practices of Nematode Control Walia CCSHAU

2. Terminology • Pi = Initial Nematode Population • Pt = Threshold level (ETL, Damaging level, Pathogenic level) • Pf = Final Nematode Population Nematode control required only if Pi > Pt Nematode Control - aims at eradication Nematode Management – aims at keeping the nematode population below Pt Walia CCSHAU

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4. Methods of Nematode Management • Cultural • Physical • Chemical • Host resistance • Regulatory • Biological • Integrated Walia CCSHAU

5. Cultural Methods • Crop rotation • Growing a non-host crop in between two susceptible ones • Non-host crop must be economically viable, locally acceptable and should not promote any new pest of disease problem • Rotation of wheat with gram, mustard for the control of Heterodera avenae Walia CCSHAU

6. Crop Rotation Wheat - Wheat Fenugreek - Wheat Wheat - Wheat Oats - Wheat Walia CCSHAU

7. 2. FALLOWING Cultural Methods • Fallowing • PPNs are obligate parasites, cannot survive without food • Flooding • PPNs are aerobic; they will die due to asphyxiation in flooded lands KEEPING THE FIELD BLANK Walia CCSHAU

8. Cultural Methods • Propagation through healthy planting material • Many nematode diseases spread through infected planting material; burrowing nematode in banana suckers, citrus nematode in infected citrus saplings, earcockle disease of wheat with contaminated seed • Removal or destruction of infected plants • Removal and destruction of root stubbles soon after harvest • Organic manuring/Amendments • Decomposition products (fatty acids) are toxic to PPNs • Increase in the population of micro-organisms, including nematode antagonists • Improved plant growth leads to tolerance against nematode damage Walia CCSHAU

9. Cultural Methods • Trap crops • Nematodes penetrate but fail to develop inside some crops like Crotalaria; can be used as green manure after a few days • Antagonistic crops • Root exudates of certain crops contain nematoxic compounds • Onion • Garlic • Tagetes (ᾳ-terthienyl) • Asparagus (asparagusic acid) • Can be used as interculture Walia CCSHAU

10. Cultural Methods • Time of sowing • Advancing crop sowing by 2-3 weeks to escape nematode infection; older crop suffer less damage even if infection occurs • Soil solarization • Deep summer ploughing • Plastic mulching Walia CCSHAU

11. Physical methods • Most nematodes cannot tolerate temperature > 50-60 C • Hot water treatment of infected plant material (bulbs, corms, tubers, rhizomes runners, seeds etc. ) is highly successful • Temperature-Time combinations are to be standardized for each crop/material • Examples • HWT of bulbs of ornamental crops against Stem & Bulb nematode, Ditylenchusdipsaci • White tip disease of rice against white tip nematode, Aphelenchoidesbesseyi Walia CCSHAU

12. Chemical control • Involves use of Nematicides or Nematocides • Pre-requisites • When Pi is very high • Crop is valuable • Quick results are warranted • Generally discouraged because of • Residue problems in edible parts • Environmental pollution • Toxicity to non-target organisms • Resurgence of pest problems • Cost considerations Walia CCSHAU

13. Classification of Nematicides Walia CCSHAU

14. Fumigants • Highly volatile halogenated hydrocarbons • Upon application into soil, turn into gaseous phase and diffuse through soil pore spaces • Kill nematodes due to blocking enzymes by substitution with halogen moieties • Used extensively during 1950-60s • Examples • DD – Dichloropropane and dichloropropene • EDB – Ethylene dibromide • MBr – Methyl bromide • 1,3 D – 1,3 dichloropropene • DBCP - Dibromochloropropene Walia CCSHAU

15. Problems involved with Fumigants • Require high doses which are phytotoxic, hence need pre-plant application • Waiting period of 3-5 weeks • Need special applicators • Need soil surface sealing with covers • Need special field preparations • Efficacy dependant upon edaphic factors • Some proved carcinogenic and leave residues in fruits Walia CCSHAU

16. Non-fumigants • Advantages • Effective against insects also • Effective at low dosages • Easy to apply and handle • Less phytotoxic an can be applied to standing crops • Mostly systemic in nature • Relatively non-volatile Walia CCSHAU

17. Organophosphates Walia CCSHAU

18. Effect of Carbofuran against CCN in Wheat Untreated Carbofuran Walia CCSHAU

19. Economising Nematicidal Use • Seedling bare root dip treatment • Seed treatment • Coating, Dipping • Nursery bed treatment • Row treatment in widely spaced crops • Spot/basin area treatment in perennials Walia CCSHAU

20. Host Resistance • Effective, Economical and Environmentally safe • Steps involved in breeding a disease resistant variety • Devising techniques for assessment of resistance • Screening of large germplasm, including wild species in some cases • Study of inheritance of resistance • Breeding resistant lines through cross/back cross, which have commercial traits • Rigorous testing under field conditions Walia CCSHAU

21. Nematode Resistant Crop Varieties Walia CCSHAU

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23. Regulatory Method - Quarantine • Legal enforcement to prevent introduction or check further spread of pests/diseases • Directorate of Plant Protection, Quarantine and Storage (Ministry of Agriculture, GOI), through DIP Act • International • Plant Protection Inspectors at all airports, seaports and landports for commercial material • Research material inspected by NBPGR, NBAGR • Domestic • Golden Nematode of Potato included in DIP Act 1971 Walia CCSHAU

24. Biological Control • Classical biological control: Action of predators, parasites and pathogens to control pests • Ambit of biological control expanded now-a-days to include several other mechanisms, including antibiosis, host resistance etc. • Natural bio-control : Antagonistic biotic interactions among co-habiting natural populations of organisms • Introduced Biological Control • Inoculative release • Inundative release Walia CCSHAU

25. Nematode Antagonists • Predators • Collemboles • Tardigrades • Enchytreids • Protozoa • Predatory mites • Predacious nematodes • Mononchus • Seinura • Predacious fungi Walia CCSHAU

26. Predacious fungi Examples Sticky hyphae : Stylopage Sticky knobs: Arthrobotrys Non-constricting rings: Dactylella Constricting rings: Dactylaria Walia CCSHAU

27. Parasites • Fungi • Egg parasites • Paecilomyces lilacinus • Pochonia chlamydosporia (Verticillium chlamydosprium) • Female parasites • Nematophthora gynophila • Vermiform stages • Catenaria Walia CCSHAU

28. Parasites • Bacteria • Pasteuria penetrans Walia CCSHAU

29. Other Antagonists • Bacteria • Pseudomonas fluorescens • Bacillus subtilis • Azotobacter chroococcum • Glucoacetobacter diazotrophicus Walia CCSHAU

30. Integrated Nematode Management • INM seeks to stabilize pest nematode population below damaging levels (Pt) through integration of various unilateral and effective practices leading to a long-term package programme or schedule based on ecologically sound, economically viable and acceptable principles Walia CCSHAU

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