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plant_parastic_nematodes and their management
- 1. Introduction to Plant Introductionto Plant Parasitic Nematodes Parasitic Nematodes and Their Management and Their Management
- 2. Nematodes Nematodes • Phylum Nematoda PhylumNematoda • Roundworms Roundworms • Microbial Feeders Microbial Feeders • (90% plus) (90% plus) • Animal Parasitic Animal Parasitic • Human Parasitic Human Parasitic • Insect Parasitic Insect Parasitic • Plant Parasitic Plant Parasitic
- 3. Plant-Parasitic Plant-Parasitic Nematodes Nematodes • Over 6000known Over 6000 known species species • Present in all ecological Present in all ecological niches niches • Attacks almost all plants Attacks almost all plants • Cause 10% losses to Cause 10% losses to crops crops • Reduces ornamental Reduces ornamental growth growth • Serious turf problems Serious turf problems • Big problem on tree Big problem on tree crops crops
- 4. Plant-parasitic nematodes allhave stylets (spears) that penetrate cells and withdraw the contents.
- 5. Nematode Nematode Names Names • Plantnematodes have both Plant nematodes have both common common and and scientific scientific names, some of economical names, some of economical importance, by common name, are: importance, by common name, are: Root-knot, Sting, Stubby-root, Reniform, Root-knot, Sting, Stubby-root, Reniform, Lance, Ring, Lesion, Burrowing, Citrus, Lance, Ring, Lesion, Burrowing, Citrus, Spiral, and Cyst Spiral, and Cyst
- 6. Feeding Habits Feeding Habits Nematodesmay be grouped by feeding habit as: Nematodes may be grouped by feeding habit as: • Endoparasitic Endoparasitic– entire body inside the root – entire body inside the root • Ectoparasitic Ectoparasitic– entire body outside the root – entire body outside the root • Semi-endoparasitic Semi-endoparasitic- part of body inside root - part of body inside root By movement when feeding, they are called: By movement when feeding, they are called: • Sedentary Sedentary – mostly immobile during their life – mostly immobile during their life • Migratory Migratory – mobile for all their life. – mobile for all their life.
- 7. Feeding Habits ofSome Feeding Habits of Some Plant-parasitic Nematodes Plant-parasitic Nematodes Root-knot Lesion
- 8. Cyst Feeding Habits ofSome Feeding Habits of Some Plant-parasitic Nematodes Plant-parasitic Nematodes
- 9. Feeding Habits ofSome Feeding Habits of Some Plant-parasitic Nematodes Plant-parasitic Nematodes Stubby root
- 10. Nematode Damage Nematode Damage •Nematodes damage plants by Nematodes damage plants by reducing or modifying root mass reducing or modifying root mass • Root cells are killed or modified to Root cells are killed or modified to serve as food for the nematode serve as food for the nematode • Typical root and foliar symptoms Typical root and foliar symptoms result result
- 11. • Water andNutrient Stress – Water and Nutrient Stress – • Premature Wilting Premature Wilting • Leaf Yellowing (Chlorosis) Leaf Yellowing (Chlorosis) • Plant Stunting Plant Stunting Foliar Damage Symptoms Foliar Damage Symptoms
- 12.
- 13. Foliar Symptoms- Foliar Symptoms- PlantDeath Plant Death
- 14.
- 15. Foliar Symptoms- Foliar Symptoms- LeafYellowing Leaf Yellowing
- 16.
- 17. Root Root Damage Damage Symptoms Symptoms •Galled Roots Galled Roots • Stunted Roots Stunted Roots • Swollen Root Tips Swollen Root Tips • Root Lesions Root Lesions • Increase in Lateral Roots Increase in Lateral Roots
- 18. Root Symptoms- Galling RootSymptoms- Galling
- 19. Root Symptoms- Cyst RootSymptoms- Cyst Nematodes on Roots Nematodes on Roots
- 20.
- 21. Root Symptoms – RootSymptoms – Sweet Potatoes Sweet Potatoes
- 22. Root Symptoms- Root Symptoms- PotatoRot Nematode Potato Rot Nematode
- 23.
- 24. Disease Interactions Disease Interactions •Nematodes cause plant disease and can Nematodes cause plant disease and can make fungal and bacterial diseases worse. make fungal and bacterial diseases worse. An example is Fusarium wilt where root-knot An example is Fusarium wilt where root-knot nematodes create entry points for the fungus. nematodes create entry points for the fungus. Control Fusarium(F) Mi +(F) Mh +(F) Mj +(F)
- 25. Problem Identification Problem Identification •Combinations of: Combinations of: • Foliar Symptoms Foliar Symptoms • Roots Symptoms Roots Symptoms • Cropping History Cropping History • Laboratory Analysis Laboratory Analysis
- 26. Management Management Methods Methods • Exclusion/Quarantine Exclusion/Quarantine •Sanitation/Clean seed/Cleaning of farm implements Sanitation/Clean seed/Cleaning of farm implements • Rotation Rotation • Plant Resistance/Resistant varieties Plant Resistance/Resistant varieties • Fallow Fallow • Organic manure Organic manure • Enemy plants Enemy plants • Trap crops Trap crops • Biological control Biological control • Sterilization with steam Sterilization with steam • Solarization Solarization • Chemical control/Nematicides Chemical control/Nematicides
- 27. Exclusion/Sanitation Exclusion/Sanitation • Buy orgrow transplants that are Buy or grow transplants that are nematode- nematode- free. free. • Use nematode-free soil or potting Use nematode-free soil or potting medium medium • Clean tools and equipment when Clean tools and equipment when changing areas or fields changing areas or fields • Remove infected plant roots Remove infected plant roots
- 28. Rotation Rotation • Move gardento a new location Move garden to a new location • Rotate grasses with broadleaf plants Rotate grasses with broadleaf plants • Plant cover crops that are poor hosts Plant cover crops that are poor hosts • Keep weeds in check, many are hosts Keep weeds in check, many are hosts • Maintain high organic matter levels Maintain high organic matter levels • Irrigate frequently and use higher Irrigate frequently and use higher fertilizer rates fertilizer rates
- 29.
- 30. Resistance Resistance • Resistance breedinghas been mainly to Resistance breeding has been mainly to root-knot nematode root-knot nematode ( (Meloidogyne spp. Meloidogyne spp.) ) • Resistance, however, may be to only 1 Resistance, however, may be to only 1 root-knot species root-knot species • Examples of resistance can be found in Examples of resistance can be found in tomato, snap bean and some southern tomato, snap bean and some southern peas peas • Little resistance is available to other Little resistance is available to other nematode species nematode species
- 31.
- 32. Solarization Solarization • Only worksmoderately well with Only works moderately well with nematodes nematodes • Has added advantage of reducing Has added advantage of reducing weed problems weed problems • Use clear plastic, make sure soil is Use clear plastic, make sure soil is tilled and moist tilled and moist • Use in the hottest months and leave Use in the hottest months and leave 6-8 weeks 6-8 weeks
- 33.
- 34. Nematode trapping fungi Nematodetrapping fungi
- 35. Fallow Sanitation Solarization Resistance Chemicals Rotation Successful Successful Nematode Nematode Control Control Fallow Solarizatio n Rotation Management Summary Management Summary •No No single single practice practice will control will control nematodes, so two nematodes, so two or more control or more control methods must be methods must be used. used. Successful Successful Nematode Nematode Control Control Sanitation Chemical s Resistance
- 36. Organic Matter Organic Matter Doescompost and organic Does compost and organic matter control nematodes? matter control nematodes? • The answer is generally The answer is generally no no, , however, they increase water and however, they increase water and nutrients available to the plant. nutrients available to the plant. • Thus, a healthier plant can Thus, a healthier plant can tolerate more nematode damage. tolerate more nematode damage.
- 37. Do nematodes causedamage Do nematodes cause damage under both wet and dry under both wet and dry conditions? conditions? • Greatest damage is caused when Greatest damage is caused when conditions are dry. conditions are dry. • Wet conditions mask some Wet conditions mask some damage until root rotting from damage until root rotting from nematode damage begins. nematode damage begins. Wet or Dry Wet or Dry
- 38. Fallow Fallow Is fallow recommendedfor nematode Is fallow recommended for nematode management? management? • Fallow makes sense because, if nematodes Fallow makes sense because, if nematodes cannot feed, they will starve, however: cannot feed, they will starve, however: • Many weeds are host to nematodes, Many weeds are host to nematodes, thus, they must not be allowed to grow. thus, they must not be allowed to grow. • At least one growing season of fallow must be At least one growing season of fallow must be used and fallow depletes soil organic matter used and fallow depletes soil organic matter • During the ‘winter’, most nematodes are During the ‘winter’, most nematodes are relatively dormant and do not feed anyway. relatively dormant and do not feed anyway.
Editor's Notes
- #2 Nematodes – Nematodes are small, mostly microscopic, nonsegemented roundworms. However, sizes range widely, and animal parasitic nematodes are generally largest. The vast majority of nematodes are beneficial microbial feeders and reside in the soil. They help promote healthy soil environments, that includes nutrient recycling. Other nematodes, such as insect feeders, provide benefits through reduction in populations of insects, e.g. mosquitoes, that are harmful to plants, animals and man. (The drawing shows the morphology of a typical plant-parasitic nematode. Note that some nematodes swell and are not vermiform (wormlike) during parts of their life cycle. This drawing is of a ‘ring’ nematode, it is widely found and quite damaging in golf courses and home lawns.
- #3 Plant Nematodes – The study of plant-parasitic nematodes is relatively young compared to study of plant diseases and insects. Thus, there is still very much to be learned. However, we know that nematodes parasitize a huge number of plants (if not all) and cause billions of dollars worth of damage to world food crops as well as tree crops, turf and ornamentals. Damage or potential damage from nematodes must always be considered when producing plants. (The photos show palm trees declining with eventual death from the ‘red ring’ nematode disease. The nematodes are transmitted by the palm weevil.
- #4 Stylet – Plant-parasites possess a stylet (spear) which differentiates them from other groups of nematodes. The stylet is used to puncture plant cell walls and membranes to allow withdrawal of cell contents. Stylets of most plant nematodes are hollow which provides a channel for cell contents to pass. A few have solid stylets that contain groves on the outside for this purpose. The general feeding process is: 1) the stylet pierces a cell; 2) digestive glands (esophageal glands) discharge enzymes which partially dissolve cell contents; then 3) contents are sucked by the action of the pumping bulb (median bulb) into the intestines (no stomach).
- #5 Nematode Names – Plant nematodes are generally given common names according to either damage symptoms they produce on plants or some striking morphological feature they possess. For example, root-knot nematodes produce root ‘knots’ while stubby root nematodes cause ‘stubby’ looking roots. The cuticle of ring nematodes looks like a stack of coins giving it a ‘ringed’ appearance, while lance nematodes have a robust stylet, resembling a ‘lance’.
- #6 Feeding Habits. Nematode feeding habits are described according to whether they feed inside or outside a root and if they move or not while feeding.
- #7 Feeding Habits –Root-knot nematodes are sedentary and endoparasitic while the lesion nematode is migratory and endoparasitic. Note that the root-knot nematodes swell and appear pear-shaped, and thus, become sedentary.
- #8 Feeding Habits – Cyst nematodes are sedentary and semi-endoparasitic while ring nematodes are sedentary and ectoparasitic.
- #9 Feeding Habits – The stubby-root nematode is migratory and ectoparasitic while reniform nematodes are sedentary and semi-endoparasitic. Most nematodes initiate feeding just behind tips of young roots. However, some like the stubby-root nematode feed directly on the root tip, generally preventing further root elongation – hence stubby roots.
- #10 Nematode Damage – Nematode damage is mainly a function of reduction of plant root mass. The feeding activities of most plant nematode result in plant root destruction, thereby limiting water and nutrient uptake by the plant. However, some nematodes cause the production of giant or nurse cells whose sole purpose is to feed the nematode (for example, root-knot nematodes). These nematodes not only physically damage a root from their activities but also redirect plant food for themselves.
- #11 Foliar Symptoms - Damage from nematodes in plant foliage may be manifest directly from feeding activity on leaves, flowers and stems. Foliar feeding nematodes, however, are much less prevalent than those feeding on roots. Root feeding nematodes produce foliar symptoms that mirror root damage. In fact, most foliar-induced symptoms are the same as those plants show when not receiving sufficient water and nutrients – wilting, yellowing, and stunting. As a result, nematode problems are often misdiagnosed and blamed on a lack of fertilizer and water.
- #12 Damage Patterns – Unlike the previous slide, most nematode damage will result in stunted, yellowing or both symptoms on plants. Areas of damage in a field are spotty across a field and irregular, usually oval, in shape. Nematodes almost never produce ‘row’ patterns.
- #13 Plant Death – These grape tomatoes are in the last stages of decline/death due to root-knot nematodes. Nematodes do not usually kill plants outright but rather lead to a slow decline sometimes leading to death.
- #14 Stunting – Cabbage plants in rows shown in this slide are the same age and planted on the same day. A nematicide was used to kill ‘sting’ nematodes before planting the cabbage on the left.
- #16 Stunting – The cabbage plant on the left simply looks young, not necessarily nematode damaged. However, it is greatly stunted compared to the same age plant on the right.
- #17 Root Damage Symptoms – Nematode damage on roots is only readily diagnosed in a few cases. For example, presence of root swellings or galls would usually indicate that root-knot nematodes are present. Also, plant root systems that show stubby and swollen root tips are typical of sting and stubby root nematode damage. However, most nematode damage simply results in stunted root systems or roots that show areas of dead tissue (lesions). These symptoms could be caused by a variety of other causal agents. For accurate problem determination, nematodes must be extracted and identified in a laboratory. Slide 22. Root Damage Symptoms – Nematode damage on roots is only readily diagnosed in a few cases. For example, presence of root swellings or galls would usually indicate that root-knot nematodes are present. Also, plant root systems that show stubby and swollen root tips are typical of sting and stubby root nematode damage. However, most nematode damage simply results in stunted root systems or roots that show areas of dead tissue (lesions). These symptoms could be caused by a variety of other causal agents. For accurate problem determination, nematodes must be extracted and identified in a laboratory. Slide 23. Root Galling – Root-knot nematodes are widely distributed and major soil pests worldwide. These nematodes cause plant cells to multiply rapid producing ‘knot’ (galls) on roots. Females are imbedded inside these galls. As indicated, root galling is easily observed and quite diagnostic for presence of these nematodes.
- #18 Root Galling – Root-knot nematodes are widely distributed and major soil pests worldwide. These nematodes cause plant cells to multiply rapidly producing ‘knots’ (galls) on roots. Females are imbedded inside these galls. As indicated, root galling is easily observed and quite diagnostic for presence of these nematodes.
- #19 Cysts on Roots – Cyst nematodes do not cause major malformations or lesions on roots. However, their swollen bodies are on the outside the root. By careful examination with a magnifying glass, ‘pearly’ white cysts on the roots can be seen.
- #20 Root Lesion - Root lesions may be caused by any number of factors. Among these are nematodes, primarily lesion and burrowing, that produce dead areas on roots. For accurate diagnosis, however, soil and root samples must be analyzed in a laboratory.
- #21 Sweet Potatoes - Nematodes not only damage roots, thus affecting plant growth, but also other plant parts present in soil. Root and tuber crops are affected in appearance and quality as well as quantity produced. Pictured here are sweet potatoes infected with root-knot nematodes resulting in a serious reduction in both appearance and quality.
- #22 Potato Rot - The ‘potato rot’ nematode causes accelerated tuber rotting as shown in this photograph. Tubers infected with these nematodes are a total loss
- #23 Root Sprangling - Nematodes are a major problem on some root crops, reducing yield and resulting in rotting but sometimes more importantly, growth distortion. For example, even low populations of nematodes can cause root ‘sprangling’ on crops such as carrots and turnips, thus rendering them unmarketable.
- #24 Disease Interactions - Nematodes not only cause plant disease by themselves but also increase plant damage caused by other disease-causing organisms such as bacteria and fungi. For example, the presence of nematodes provides entry points for invasion of Fusarium wilt fungi in a number of crops. (Note in the photograph that presence of the Fusarium wilt fungus showed little affect on plant growth, but damage dramatically increased in the presence of root-knot nematodes (Mi, Mh, and Mj).
- #25 Problem Identification – To identify a nematode problem, one must consider individual plant foliar and root symptoms, field damage patterns, plus have an idea of cropping history (were susceptible crops previously grown?). If nematodes are suspected, a final laboratory analysis is often needed to confirm suspicions.
- #26 Management - Methods for nematode management are generally broken down into: 1) exclusion, 2) sanitation, 3) cultural practices, 4) plant resistance, and 5) nematicides. The heading, cultural practices, is not listed in the slide. Rather, those cultural practices of rotation, solarization, and fallow are listed separately. This was done to emphasize the importance of these techniques, particularly where use of nematicides are prohibited or not available.
- #27 Exclusion/Sanitation – Keep pests out!! For example, buy or grow transplants that are nematode-free. The soil medium is obviously the greatest consideration here and it should be nematode-free. Remove potentially contaminated soil and plant materials from tools and other equipment when moving from one area or field to another. For nematodes, this is usually just a matter of rinsing tools thoroughly with water.
- #28 Rotation – This ‘cultural practice’ can/should be a cornerstone of any nematode management program. In most annual crops, proper crop rotation with non- or poor hosts of nematodes is the only nematode management needed. However, economics of growing ‘rotation’ crops, practicality including land requirements, and specific nematode host range many times limits rotation options. This practice should always be keep in mind, even in small garden plots, where perhaps sweet corn could be rotated with more susceptible crops such as okra.
- #29 Soybean Rotation – Planting a poor or nonhost of nematodes for two years will generally reduce nematode populations and allow acceptable plant growth of a susceptible crop.
- #30 Resistance - The use of plant resistance, when available, should always be encouraged. Resistance to root-knot nematodes is available in crops such tomato, soybean, snap bean, southern peas and several other crops. A word of caution, do not rely solely on plant resistance since certain populations of nematodes can overcome resistance beginning either immediately or sometimes several years after regularly planting the resistant plant.
- #31 Resistant/Not Resistant – The process of finding, breeding and selecting plants with resistance to nematodes is long and tedious. The plant on the left shows good resistance to root-knot nematodes as evidenced by lack of galling, note the susceptible, galled root system on the right.
- #32 Solarization – This practice dramatically increases soil temperatures which in turn kills many weed, fungal, insect and nematode pests. Temperatures that kill nematodes are reached only in the first six inches or so of soil leaving living nematodes present at lower depths. Thus, correct use of solarization will reduce nematode populations, but not enough to prevent all nematode damage to crop plants. It is only useful to minimize nematode damage but should be used in combination with other management practices.
- #33 Laying Clear Plastic – Solarization increases soil temperatures and these temperatures kill nematodes. l Soil temperatures that kill nematodes, however, are only reached to depths of 6-8 inches. Remaining nematodes below this depth are usually present in high enough numbers to still cause plant damage.
- #35 Management Summary - At least two management practices must be used to minimize nematode damage. In addition, good crop husbandry practices such as addition of organic matter, good soil fertility and irrigation will also help reduce nematode damage.