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Nematode Damage Rarely, does a single nematode pose a threat to a plant. (exceptions - virus vectors and sting nematodes) Rarely, does a single nematode.

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Presentation on theme: "Nematode Damage Rarely, does a single nematode pose a threat to a plant. (exceptions - virus vectors and sting nematodes) Rarely, does a single nematode."— Presentation transcript:

1 Nematode Damage Rarely, does a single nematode pose a threat to a plant. (exceptions - virus vectors and sting nematodes) Rarely, does a single nematode pose a threat to a plant. (exceptions - virus vectors and sting nematodes) Damage to plant parts results from many nematodes feeding at once. Damage to plant parts results from many nematodes feeding at once. The root system of plants can be growing in the presence of hundreds of thousands or even millions of nematodes. The root system of plants can be growing in the presence of hundreds of thousands or even millions of nematodes.

2 Nematode Damage Quite often it is very difficult to see symptoms caused by nematode (even though yield loss may be reduced by 30%). Quite often it is very difficult to see symptoms caused by nematode (even though yield loss may be reduced by 30%). This is compounded by the fact that nematodes are rarely normally distributed in a field. This is compounded by the fact that nematodes are rarely normally distributed in a field. Nematode damage can be confused with herbicide and other chemical injury. Nematode damage can be confused with herbicide and other chemical injury.

3 Damage Mechanical injury results from the nematode stylet puncturing the cell wall, and is followed by the secretion of enzymes and nutrient extraction. This process leaves cells that are damaged or completely destroyed. Mechanical injury results from the nematode stylet puncturing the cell wall, and is followed by the secretion of enzymes and nutrient extraction. This process leaves cells that are damaged or completely destroyed. Nematode damage can result in a variety of symptoms: Nematode damage can result in a variety of symptoms: 1. Lesions 2. Galls or swellings 2. Galls or swellings 3. Stunted plants 4. Loss of vigor 5. Excessive root branching 5. Excessive root branching 6. Twisted or distorted stems and/or leaves 6. Twisted or distorted stems and/or leaves 7. Disruption in flower development / sterility 7. Disruption in flower development / sterility 8. Dead or incapacitated root tips Disease Complexes - While nematodes are devastating pathogens, their most significant influence in agriculture results from their participation in pathogen complexes. Disease Complexes - While nematodes are devastating pathogens, their most significant influence in agriculture results from their participation in pathogen complexes.

4 Damage

5 Damage

6 Nematodes as Plant Pathogens Endoparasites Endoparasites Vermiform all stages Vermiform all stages Lesion nematode Lesion nematode Pine wilt nematode Pine wilt nematode Swollen females Swollen females Cyst nematodes Cyst nematodes Root knot nematode Root knot nematode Ectoparasites Ectoparasites Dagger nematode Dagger nematode Management Management

7 ENDOPARASITES ECTOPARASITES Root-lesion nematodes Dagger nematodes Root-knot nematodes Reniform nematodes

8 Taxonomy Kingdom Animalia Phylum Nemata Class Secernentea Class Secernentea 5 other orders contain free-living forms and parasites of animals Order Aphelenchida - parasites of higher plants (usually on above ground parts), fungi, and insects Important genera: Aphelenchoides - foliar nematode Bersaphelenchus - pine wilt nematode Order Tylenchida - parasites of higher plants, insects, and fungi – largest % of plant pathogens Important genera: Heterodera spp. - cyst nematodes Meloidogyne spp. - root-knot nematodes Pratylenchus spp. - root-lesion nematodes

9 Taxonomy Kingdom Animalia Phylum Nemata Class Adenophorea (as opposed to Secernentea) 11 other orders contain free-living forms and parasites of animals and microorganisms Order Dorylaimida - plant parasites/virus vectors (Stylet without knobs and no distinct median bulb) Important genera: Xiphinema spp.- dagger nematode Longidorus spp.- needle nematode Trichodorus spp.- stubby-root nematode

10 Root lesion nematodes Pratylenchus spp. Pratylenchus spp. 7 important species in United States 7 important species in United States Most plants are susceptible to one or more species Most plants are susceptible to one or more species Migratory endoparasite, can leave and reenter the roots many times in its lifecycle. Migratory endoparasite, can leave and reenter the roots many times in its lifecycle. Males may or may not participate in reproduction. Males may or may not participate in reproduction.

11 Root lesion nematodes

12 Pine wilt nematode Bursaphelenchus xylophilus Bursaphelenchus xylophilus Hosts - Scots, Austrian, jack, mugo, and red pines and, less commonly, white pines Hosts - Scots, Austrian, jack, mugo, and red pines and, less commonly, white pines Interaction between a nematode, insect, sometimes fungi Interaction between a nematode, insect, sometimes fungi

13 Attacks Pines at Any Age

14 Few vs. the Many

15 Disease Cycle

16 Vector on Healthy Plant

17 Nematodes in the Trachea of Vector

18 Cyst nematodes Heterodera spp. Heterodera spp. H. schactii – sugar beet cyst nematode H. schactii – sugar beet cyst nematode H. glycines – soybean cyst nematode – $3 billion in damage/year H. glycines – soybean cyst nematode – $3 billion in damage/year All are sedentary, endoparasites All are sedentary, endoparasites After J2 stage enters the root and establishes a smaller feeding site than root-knot nematode. No gall production. After J2 stage enters the root and establishes a smaller feeding site than root-knot nematode. No gall production. After the J2 becomes an adult, males leave the root to fertilize the females that have protruded through the root. After the J2 becomes an adult, males leave the root to fertilize the females that have protruded through the root. The female will swell upon maturity producing several hundred eggs outside and inside of her body. When she dies (4 wks old) her body will become a protective cyst for her young. The female will swell upon maturity producing several hundred eggs outside and inside of her body. When she dies (4 wks old) her body will become a protective cyst for her young. Some eggs will hatch immediately, some later in the season, next year or years, or never. Some eggs will hatch immediately, some later in the season, next year or years, or never.

19 Soybean cyst nematode

20 Soybean cyst nematode disease cycle

21 Soybean cyst nematode No visible symptoms with 30% yield loss Visible symptoms with % yield loss

22 Root-knot nematode Meloidogyne spp. Meloidogyne spp. M. incognita – southern-root knot M. incognita – southern-root knot M. hapla – northern root-knot M. hapla – northern root-knot All are sedentary, endoparasites All are sedentary, endoparasites After J2 stage enters the root and establishes giant cells (cells enlarge and rapidly divide) creating a more efficient nutrient sink for the nematode = gall production. After J2 stage enters the root and establishes giant cells (cells enlarge and rapidly divide) creating a more efficient nutrient sink for the nematode = gall production. After the J2 becomes an adult, males leave the root. The female will swell upon maturity producing several hundred eggs. Males may or may not participate in reproduction. After the J2 becomes an adult, males leave the root. The female will swell upon maturity producing several hundred eggs. Males may or may not participate in reproduction. Population is managed by the ratio of females : males that are produced. Immature females can change to males if the population density can not be supported. Population is managed by the ratio of females : males that are produced. Immature females can change to males if the population density can not be supported.

23 Root-knot nematode Juveniles in root Male, hatching from cuticle Giant cell Gall, with female protruding

24 Root-knot nematode

25 Root-knot Nematode

26 Dagger nematodes Xiphinema spp. Xiphinema spp. 3 important species in United States 3 important species in United States Characterized by long body and stylet. Characterized by long body and stylet. Sedentary ectoparasite. Feeds only at the root tips. Sedentary ectoparasite. Feeds only at the root tips. Feeding produces knobby, stunted roots. Feeding produces knobby, stunted roots. Males are required for reproduction, females produce very few eggs, but lives several months (most other nematodes live a few weeks). Males are required for reproduction, females produce very few eggs, but lives several months (most other nematodes live a few weeks).

27 Dagger nematodes

28 Stunted plants Stubby roots Carmi, IL

29 Dagger nematodes (grape fan leaf virus)

30 Management Strategies I. Cultural practices - Includes agricultural tactics that indirectly influence pathogen populations and communities. a. Crop rotation b. Trap crops c. Fallow e. Flooding or heat f. Tillage g. Planting date g. Planting date

31 Management Strategies II. Breeding for resistance The use of nematode resistant varieties is a major management strategy. In many crops, chemical control is not economically viable and breeding is the only available tactic. The use of nematode resistant varieties is a major management strategy. In many crops, chemical control is not economically viable and breeding is the only available tactic. One of many limitations is that where races of nematodes are problematic (such as soybean cyst nematode and root-knot nematode), effective control of nematode populations occurs only when the plant contains resistant genes against the specific race present.

32 Management Strategies III. Biocontrol The use of fungi, bacteria, viruses, other nematodes,to manage nematodes. The are many examples of biocontrol of nematodes, however, very few work in the field. Bacterium - endospore forming Pasteuria penetrans Fungus - adhesive rings by Arthrobotrys spp.

33 Management Strategies IV. Chemical control The use of pesticides or other chemicals to reduce or eliminate nematode populations. Nematicides - are used to manage nematode populations on high value crops. The use of nematicides is being reduced because of toxicity to the environment and to humans. examples – Methyl Bromide, Vapam, Telone, Temik, Mocap, Counter


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