1. Nematode Management for Landscape Ornamentals
William T. Crow
Landscape Nematologist
University of Florida

2. What are nematodes? Unsegmented roundworms Aquatic Small
Nematodes are unsegmented roundworms. This makes them different from earthworms which are segmented. An earthworm can be broken in two and both ends wiggle because they have segments that separate their body into compartments. A nematode’s body is all one piece and under pressure, just like an elongated balloon. An attempt to break a nematode in two would result in a violent expulsion of its insides.
All nematodes are aquatic. Nematodes living in soil are in microscopic films of water that surround soil particles. Those inside plants live in plant juices.
Soil-nematodes are small and require a microscope to be seen. This slide shows the size of a typical soil nematode in comparison with a cotton thread.

3. Where do nematodes live?
Nematodes are found in soil and water everywhere.

4. “Good”-vs-“Bad” nematodes
Bacterial feeders
Fungal feeders
Predators
Animal-parasites
Plant-parasites
“Good guys”
People always ask if there are “good” nematodes. We think of things as being “good” or “bad” based on how they affect us.
Most nematodes feed on bacteria or fungi and are important in decomposition and nutrient cycling in nature. Some nematodes are predators, preying on microscopic animals or other nematodes.
Some of the nematodes that we think of as “bad” are animal parasites, causing diseases of humans, pets, and livestock.
The nematodes we will be discussing are the plant-parasites. These nematodes can cause damage to the ornamental plants that are an important part of the economy Florida.
“Bad guys”

5. Steinernema scapterisci
This is an example of a beneficial nematode. S. scapterisci, the mole cricket nematode, can be used to manage pest mole crickets on turf or pastures.
The white cloud surrounding this dead mole cricket is the nematodes leaving in search of another mole cricket to infect.
*Commercially available Fall, 2001

6. Predatory nematodes Mmmm Tastes like chicken!!
Some beneficial nematodes are predators of the plant-parasites. Some of these predators have a spear that they use to puncture their prey and then “suck” out the liquid contents. Others have a large mouth with teeth that they use to chew their prey up or swallow it whole.

7. Plant-parasitic nematodes
Stylet
This is a diagram of a typical plant-parasitic nematode. Plant-parasites have a stylet or “mouth spear” used to puncture plant cells. The stylet is similar to a hypodermic needle and can be used to either inject digestive juices or suck cell contents through.

8. Plant-parasitic nematodes
Ectoparasites – outside roots
Endoparasites – inside roots
There are two major types of plant-parasitic nematodes based on how they feed on plants. Ectoparasites live in the soil and feed by inserting only their stylet into the root. Endoparasites enter into the plant and feed with their body inside the plant tissue.

9. Nematode life cycle - egg
All plant-parasitic nematodes hatch from eggs. You can see this young nematode curled up within its egg.

10. Nematode life cycle - hatching
After the plant-parasitic nematode hatches from the egg it follows chemical signals that attract it to a host root.

11. Ectoparasites- feeding
The nematodes usually attack young fibrous roots. These ectoparasites are swarming around a root tip and feeding on it.

12. Ectoparasites- feeding
Stylet
Ectoparasites feed by inserting their stylet into root tissues.

13. Endoparasites
Endoparasitic nematodes enter into the root with their body.

14. Migratory endoparasites
Migratory endoparasites such as these will then burrow around inside the root, feeding as they go from cell to cell.
Nematodes

15. Nematode eggs
The migratory endoparasites lay their eggs within the root. The next generation will then hatch out ready to start feeding.

16. Sedentary endoparasites
Egg mass
Sedentary endoparasites, like this root-knot nematode, establish a permanent feeding site. The nematode then stays in one spot feeding on the specialized cells in the feeding site. Because the nematode doesn’t have to move anymore they can lose their worm-shape and turn into an egg-laying machine. This female root-knot nematode looks like a beach ball. She lays her eggs in an egg mass at the root surface. Each egg mass usually contains hundreds of eggs.
Nematode

17. Above-ground symptoms of root nematodes
Wilting
Yellowing
Stunting
Thinning
Death
These are visual, above-ground symptoms of nematode damage to plants. These symptoms are very non-specific and may be identical to symptoms of water stress, nutrient deficiency, physiological stresses or fungal root diseases.

18. Wilting Incipient Wilting
Often plants whose roots have been injured by nematodes may wilt even when enough moisture is present. Often the plants will wilt while the sun is hitting them and then seem to recover in the evening. This is called “insipient wilting”.
Incipient Wilting

19. Declining
Plants rely on roots to obtain the water and nutrients needed to support the rest of the plant. When the roots are damaged by nematodes they cannot function properly and the plant may exhibit symptoms of water or nutrient stress. What looks like drought symptoms in this picture is caused by root-knot nematode damage to roots.

20. Yellowing, stunting With nematodes Without nematodes Yellowing foliage
The gardenia plant on the left is showing symptoms of nutrient deficiency. However, a lack of nutrients in the soil is not causing the problem. The plant cannot take up the nutrients that are there because its roots have been damaged by root-knot nematodes.
Yellowing foliage

21. Thinning Sparse canopy Root-knot nematodes on bottlebrush
Because they cannot get enough water through their damaged roots the plant may not be able to support a large amount of foliage. This bottlebrush has a thin, sparse canopy resulting from nematode injury to its roots.
Root-knot nematodes on bottlebrush

22. Thinning, declining Sparse canopy Root-knot nematodes on pittosporum
The same is true for this pittosporum. Can you see that it would be impossible to tell what is causing the problem simply by looking at the above-ground portions of the plant?
Root-knot nematodes on pittosporum

23. Damage in patches Root-knot nematodes on boxwood
Often nematode damage occurs in patches. In a hedge a few damaged plants may occur among healthy plants.
Root-knot nematodes on boxwood

24. Root-knot nematode Sedentary endoparasite Causes root galls
Rotting roots
Root-knot nematodes are probably the most well known of the plant-parasitic nematodes. These nematodes secrete hormones that cause galls or knots to develop from the plant tissue surrounding them. These galls are fairly characteristic and are the most easily recognizable of all the nematode symptoms.
The nematodes also cause disruption in the root tissue which allow fungi to enter. Root-knot nematodes can produce chemicals that make the plant more susceptible to fungi. These fungi may cause rotting of the roots.

25. Root-knot nematode galls
The roots on the left are galled by root-knot nematodes, the ones on the right are healthy.
With nematodes Without nematodes

26. Root-knot galls on impatiens
If you notice incipient wilting of impatiens pull them up and you often will see this. These are root-knot galls on impatiens. Impatiens are commonly damaged by these nematodes.

27. Root-knot galls on asparagus fern
Storage roots
The carrot-shaped roots on asparagus fern are normal and not caused by nematodes. However, you can see the smaller root-knot galls on the lower portions of the root system.
Galls

28. Root-knot galls on ligustrum
Ligustrum is a landscape plant that sometimes is damaged by root-knot nematodes.

29. Root-knot galls on wax myrtle
Even some native plants such as wax myrtle can be damaged by root-knot nematodes on occasion.

30. Other sedentary endoparasites
Reniform
Citrus
Cyst
Some other sedentary endoparasites that can damage landscape plants in Florida are reniform, citrus, and cyst nematodes.
While these nematodes are sedentary endoparasites they do not cause galls like the root-knot nematodes. Instead there may be discoloration or rotting of roots, or just an unthrifty root system.
Reniform nematodes

31. Reniform nematodes “Sticky” egg mass Nematodes
The back end of reniform and citrus nematodes are outside of the root. The egg masses produced by these nematodes are sticky, so soil often will stick to them.

32. Reniform nematode damage to roots
Reniform, citrus, and cyst nematodes cause a generally unthrifty root system with no distinct symptoms.
Without nematodes With nematodes

33. Migratory endoparasites
Lesions on roots and belowground structures
Discoloration and rotting of roots
Lesion nematode
Lesion and burrowing nematodes are migratory endoparasites. They tunnel around inside of the root from place to place. Lesions or dark shrunken areas may appear as a result of nematode activity. These lesions closely resemble those caused by some root-rotting fungi.
These nematodes can affect citrus and many ornamental plants.
Fungi can enter into the tunnels made by the nematodes and cause rotting of the roots or other belowground plant organs.
Burrowing nematode

34. Amaryllis with lesion nematodes
Lesions
This bulb is showing symptoms of damage by lesion nematodes. Notice the dark lesions and the rotting.
Rotting

35. Amaryllis with lesion nematodes
Lesions

36. Lesion nematodes Lesions
Here is a close-up of lesion nematode damage on roots.

37. Lesion nematodes on Easter lily
Rotting
Infection by burrowing nematodes caused rotting of this Easter lily bulb.

38. Burrowing nematodes on banana
This is rotting of banana roots is caused by burrowing nematodes.

39. Burrowing nematodes on palms
Burrowing nematodes can attack many of our ornamental plants, including some palms.
This root rotting is caused by burrowing nematodes but is indistinguishable from fungal root rots.
Rotting

40. Spreading decline
Burrowing nematodes in Florida cause a disease known as spreading decline. These nematodes can kill citrus trees rapidly. Because of this, burrowing nematodes are a regulated pest in citrus nurseries.

41. Citrus slump on lime
The coffee lesion nematode causes a disease on citrus known as citrus slump. Because it is so damaging on citrus this nematode also is a regulated pest in citrus nurseries.

42. Ectoparasites Sting Stubby-root Sheath Awl Spiral
These are a few of the ectoparasitic nematodes that can damage plants in the landscape.
Ectoparasites can cause abbreviated “stubby” roots, or sometimes a general unthrifty root system without distinct symptoms.

43. Abbreviated “stubby” roots
This is severe stubby-root symptoms caused by ectoparasitic nematodes.
Abbreviated “stubby” roots

44. Nematode diagnosis
The only way to determine if nematodes are a problem is with a nematode assay
This is usually a separate test, and must be submitted separately from a standard disease sample
We have seen over and over that in most cases nematode symptoms can be identical to other plant problems. The only way to be certain if nematodes are causing a problem is by having a nematode assay conducted by a credible diagnostic laboratory.
For most labs this is not included in a regular disease diagnostic sample and must be specifically requested and often requires separate payment.

45. University of Florida Nematode Assay Lab
Building 78, Mowry Rd.
PO Box
Gainesville, FL
$12
The UF Nematode Assay Lab conducts nematode assays for a cost of $12 per sample.
Knowing what the problem is can help you deal with the problem, and also to avoid treating the wrong problem.

46. Nematode Sample Kit
Nematode sample kits include everything needed to submit a nematode sample and instructions. These kits are available at your county Cooperative Extension office.
Please note these are different than soil test bags. Never submit a nematode sample in a soil test bag!!

47. Nematode management
Sanitation – “an ounce of prevention is worth a pound of cure” (Quote by Dr. Crow’s Mamma, used with permission).
Plant parasitic nematodes are moved in infested planting material, soil, or water.
The current lack of effective chemical controls underscore the need to practice sanitation as the first line of defense against plant-parasitic nematodes in the landscape.
Is always preferable to avoid a potential problem than to deal with an existing one. Nematodes can be brought in on infested plant material, soil, or water.

48. Root-knot nematode galls
Often root-knot nematode galls can be observed on roots of potted nursery stock. The nematodes can then be moved into new areas when the plant is planted. It’s always a good idea to check the health of a plant’s root system before you buy it.

49. Nematode management - Sanitation -
Clean equipment after use
Replace soil
Disinfest soil
After digging in contaminated soil or removing sick plants, it is always a good idea to clean off shovels and other equipment before future use. For further insurance, equipment may be rinsed with a bleach solution (1 part bleach to 9 pasts water) to kill nematodes and fungi adhering to surfaces.

50. Nematode management -Chemicals-
Preplant soil fumigation with Dazomet
Dazomet is sold as Basamid Granular by BASF. Dazomet is incorporated into soil before planting. It is a granular material, but releases nematicidal gases as it breaks down in soil. It is fairly effective against weeds and moderately effective against fungi and nematodes.
This is a restricted use chemical that may only be used in certain applications by licensed applicators.

51. Soil Solarization Damp (not saturated) soil Clear plastic tarp
High temperatures (June, July)
1 to 2 months
Soil solarization uses heat from the sun to kill nematodes, fungi, insects, and weeds to a depth of 6 to 8 inches. The effectiveness of this method depends on soil temperature and is influenced by the amount of sunlight. This method will only work in direct sunlight when temperatures are high.
Soil must be worked and be damp, but not saturated. The soil is then covered with a clear plastic mulch and left for 1 to 2 months during the summer.

52. Replace contaminated soil
Give the plants a head start
Doesn’t last forever
For annual planting beds and other small areas it is sometimes easiest to dig up the contaminated soil and replace it with new soil or potting mix.
Eventually nematodes will re-infest the new soil, but you have bought time for your plants. Once the plants get a root system established they are better able to live with the nematodes.

53. Root barriers Keep clean roots from growing into contaminated soil
Keep contaminated roots from growing into clean soil
Using root barriers can help cut down on re-infestation. This is a special type of cloth barrier that is placed down below the soil.
Root barriers do not keep out nematodes, but keep the roots of your plants from growing out into the old soil where the nematodes are. They also keep out roots from other plants nearby. These roots may harbor nematodes and can bring in the nematodes with them.

54. Alternative planting
If a nematode-resistant or nematode-tolerant plant can identified it should be used.
This is easier said than done. It is extremely difficult to find a plant that can not be adversely affected by some nematode. Over time we hope to do extensive screening of landscape material to find out what nematodes can affect each type of plant. In the meantime there are certain kinds plants that commonly suffer from nematode damage and may be avoided in known nematode-infested areas.

55. Woody ornamental plants that are commonly damaged by root-knot nematodes in Florida
Butterfly bush
Hibiscus
Boxwood
Gardenia
Pittosporum
Ixora
Japanese holly
Rose
Lantana
These landscape plants are among the most commonly damaged by root-knot nematodes in Florida. If replacing plants that have been diagnosed with root-knot, these plants should be avoided.

56. Annual bedding plants that are commonly damaged by root-knot nematodes in Florida
Coleus
Snapdragon
Petunia
Verbena
Pansy
Portulaca
Dianthus
Impatiens
These bedding plants are among the most commonly damaged by root-knot nematodes in Florida. In planting beds where root-knot nematodes have been diagnosed these plants should be avoided.

57. Choose adapted plants
The better the overall health of the plant, the better its ability to withstand nematode pressure
Always use plants that are adapted to the conditions where you intend to grow them. This helps insure the overall health of the plant.
Some of the factors to consider when choosing plants are amount of sunlight, soil pH, drainage, irrigation, etc.

58. Dr. Billy Crow, Landscape Nematologist University of Florida
For information on nematodes, nematode management, sampling procedures, or help interpreting lab results contact:
Dr. Billy Crow, Landscape Nematologist University of Florida
P.O. Box , Gainesville, FL 32611
(352) X 138
Dr. Crow is available to answer any questions you might have regarding nematode management on ornamental plants.
He can also help in interpreting lab results from the U.F. Nematode Assay Lab or other labs you might use.

59. Mr. Frank Woods, Senior Biologist
For information on submitting samples to the UF Nematode Assay Lab, or to check on the status of a submitted sample contact:
Mr. Frank Woods, Senior Biologist
University of Florida
P.O. Box , Gainesville, FL 32611
(352)
For information on submitting samples to the U. F. Lab or to check on the status of a sample you have submitted, contact Frank Woods.

60. On-line resources Nematode management guide Featured creatures
Featured creatures
The nematode management guide for landscape plants, and other nematode management information is available on EDIS.
Information on the biology of different species of common nematodes are found on Featured Creatures