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PlantParasitic Nematodes

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Foliar Nematode Symptoms on Hibiscus Leaves Note restriction by leaf veins ... Most important and damaging nematode in southeast US and tropics ... – PowerPoint PPT presentation

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Title: PlantParasitic Nematodes


1
Plant-Parasitic Nematodes
2
Nematodes
  • Unsegmented worms
  • Usually microscopic
  • Phylum Nematoda

3
Nematodes Many different groups and habits
  • Decomposers
  • Predators
  • Insect parasites
  • Animal parasites (often host-specific)
  • Plant parasites
  • Others (freshwater, marine, etc.)

4
Nematodes Many different groups and habits
  • Decomposers
  • Predators 19
  • Insect parasites 8
  • Animal parasites 33
  • Plant parasites 7
  • Others 33

Poinar, 1983
5
Nematodes Many different groups and habits
  • Decomposers
  • Predators
  • Insect parasites
  • Animal parasites
  • Plant parasites
  • Others (freshwater, marine, etc.)

Beneficials in ag
Pests in ag
6
Plant Parasitic Nematodes Habits and Habitat
  • Ectoparasites many kinds inhabit soil around
    plant roots, feed on roots
  • Endoparasites some kinds enter roots (bulbs,
    and other below-ground plant parts) and feed
    internally
  • Semi-endoparasites partially enter into roots
  • Foliar nematodes a few kinds enter above-ground
    plant tissue (leaves, seeds, stems)

7
Foliar Nematode Symptoms on Hibiscus Leaves
Note restriction by leaf veins
8
Symptoms many are typical of plants with root
damage
  • Yield loss
  • Stunting
  • Yellowing
  • Water deficiency and wilting
  • Nutrient deficiency
  • Some direct damage (knots on roots, misshapen
    potatoes, peanuts, etc.)

9
Severe Stunting of Corn Plants by Nematodes
10
Galls or Knots on Root System
11
Life Cycle
  • Rapid life cycles (30 days at summer temp.)
  • Can build quickly to high numbers
  • Many species are good r-strategists

12
Nematode Damage depends on
  • Kind of nematodes present
  • Numbers of nematodes present
  • Environment
  • Other organisms present

13
Nematode Damage depends on
  • Kind of nematodes present
  • Numbers of nematodes present
  • Environment
  • Other organisms present

14
Root Knot Nematodes(Meloidogyne spp.)
  • Most important and damaging nematode in southeast
    US and tropics
  • Produce typical gall or knot symptoms on plant
    roots

15
Root-knot nematodes are widespread key pests
on most crops
16
Root-Knot Nematode Life Cycle
  • Juvenile nematode moves freely in soil
  • Enters root and moves to feeding site

17
Root-Knot Nematode Juvenile in Root becomes
immobile at feeding site
18
Root-Knot Nematode Female
  • Immobile nematode increases to large size

19
Root-Knot Female (with many eggs) breaks through
root surfaceEggs and juveniles continue cycle
in soil
20
Root-knot nematodes females cause the galls seen
on roots
21
Some Other Important Nematodes
  • Soybean Cyst Nematode in midwest US
  • Burrowing Nematode on bananas in tropics

22
Nematode Damage depends on
  • Kind of nematodes present
  • Numbers of nematodes present
  • Environment
  • Other organisms present

23
Numbers of nematodes present
Tolerance Limit
24
Nematode Damage depends on
  • Kind of nematodes present
  • Numbers of nematodes present
  • Environment (temp., moisture, heat units, soil
    type, etc.)
  • Other organisms present (wounding of roots can
    lead to possible interactions with plant diseases)

25
Nematode Management
  • Except for root-knot, usually need soil sample to
    confirm that nematodes are present

26
Nematode Management
  • Soilborne pest, usually site specific
  • Nematodes dont migrate freely like insects
  • Hard to get to new sites
  • Once present, always present

27
Nematode Management
  • Management is often before planting
  • Populations build up rapidly on susceptible crops
  • Usually cant react to populations on established
    crops, as with insects

28
Sanitation avoid introducing pests to new
locations
  • Clean soil
  • Clean planting material
  • Clean equipment
  • Destroy/remove residues of infected plants

29
Sanitation
  • Nematodes move easily on infected planting
    material

30
Host Plant Resistance
  • Very important since some crops and cultivars are
    poor hosts
  • Resistance low nematode reproduction on the
    plant
  • Tolerance plant withstands nematode damage

31
Nematicides
  • Fumigants or nonfumigants
  • Some fumigants are multipurpose affect insects,
    weeds, fungi as well
  • Effective and consistent
  • - - Can easily enter soil (and water) environment
    (targets are soil pests)
  • - - Methyl bromide enters atmosphere

32
Crop Rotation
  • Reduces populations in a site by growing a poor
    or non host
  • Doesnt eliminate nematodes (low numbers may
    persist for several years)
  • Objective is to lower numbers enough so that next
    susceptible crop is successful

33
Vetch Cover Crop with Weed Hosts
  • Weeds can carry nematodes through crop rotations

34
Fallow
  • Clean, weed-free fallow is a possible rotation
  • Starves nematodes, if 100 free of weeds
  • - - Serious problems with soil erosion, runoff,
    etc.

35
Heat
  • Pasteurization or steaming of soil
  • Solarization

36
Biological Control
  • Few successful examples of introduced control
    (difficult to introduce organisms into soil
    environment)
  • Natural biological control agents present in most
    soils

37
Pasteuria on Sting Nematode
  • Common bacterial parasite that attacks nematodes

38
Nematode-trapping Fungi
Experiment I
Adhesive knobs
Dactylaria brochopaga
Potential in Biocontrol
Arthrobotrys oligospora
39
Organic Amendments
  • Decomposition products may affect some nematodes
  • Improve environment for biological control
  • Amendments can benefit plant health

40
Organic Amendments
  • Decomposition products may affect some nematodes
  • Improve environment for biological control
  • Amendments can benefit plant health
  • Amendments can benefit plant whether nematodes
    are present or not --- they contain N and other
    plant nutrients !

41
Nematode Management other methods
  • Improved plant health by adding water,
    fertilizer, amendments, mulch, etc.
  • Manipulate planting dates
  • Remove weed hosts
  • Etc

42
Nematode Management No Quick Answers
  • Cant eliminate nematodes
  • No nematicides available for many crops

43
References
  • Text, pp. 196-201.
  • Andrews, J.H., and I. Tommerup. 1995. Advances in
    Plant Pathology. Vol. 11. Academic Press, San
    Diego. Ch. 8.
  • Barker, K.R. et al. 1998. Plant and Nematode
    Interactions. American Society of Agronomy,
    Madison, WI.
  • Poinar, G.O. 1983. The Natural History of
    Nematodes. Prentice-Hall, Englewood Cliffs, NJ.
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