University of FloridaSolutions for Your Life

Download PDF
Publication #ENY-038

Nematode Management for Non-Residential Lawns, Athletic Fields, Racetracks, and Cemeteries in Florida1

William T. Crow2

Turfgrasses help beautify our environment, reduce water runoff, and reduce water and air pollution. They are also essential components of many athletic fields, racetracks, and parks. Just like any other crop, pest management is key for growing healthy grass. Plant-parasitic nematodes (Figure 1) are probably the least understood and most difficult to manage of the turfgrass pests in Florida. These nematodes cause turf to decline, need more frequent irrigation, and have increased problems with weeds and other pests. Damage from nematodes to turf roots decreases fertilizer uptake, thereby indirectly contributing to potential groundwater contamination. Turf root systems on athletic fields weakened by nematodes can cause turf to pull up during play and thereby contribute to the incidence of player injuries.

Figure 1. 

Diagram of a typical plant-parasitic nematode.


[Click thumbnail to enlarge.]

What are nematodes?

Nematodes are unsegmented roundworms, different from earthworms (http://entnemdept.ufl.edu/creatures/MISC/MISC/Earthworm.htm) and other familiar worms that are segmented (annelids) or in some cases flattened and slimy (flatworms) (http://entnemdept.ufl.edu/creatures/misc/land_planarians.htm). Nematodes living in soil are very small and most can only be seen using a microscope (Figure 2). There are many kinds of nematodes found in the soil under any turf. Most of these are beneficial, feeding on bacteria, fungi, or other microscopic organisms. There are even nematodes that can be used as biological control organisms to help manage important turf insect pests. Unfortunately, there are also nematodes that feed on plants. These are called plant-parasitic nematodes (Figure 1).

All plant-parasitic nematodes have a stylet or mouth-spear that is similar in structure and function to a hypodermic needle (Figure 3). The nematode uses the stylet to puncture plant cells, and then injects digestive juices and ingests plant fluids through it. All of the plant-parasitic nematodes that are important turfgrass pests in Florida feed on roots. Some plant-parasitic nematodes remain in the soil and feed by inserting only their stylet into the root. These are called ectoparasitic nematodes (Figure 4). Others, using their stylet to puncture an entry hole in the root, feed with their body inside the root tissue. These are called endoparasitic nematodes (Figure 5). Of the common nematodes that cause damage to turfgrasses in Florida, sting (http://entnemdept.ufl.edu/creatures/nematode/sting_nematode.htm), awl (http://entnemdept.ufl.edu/creatures/nematode/awl_nematode.htm), stubby-root (http://entnemdept.ufl.edu/creatures/nematode/stubbyroot/trichodorus_obtusus.htm), sheath, sheathoid, spiral (http://entnemdept.ufl.edu/Creatures/NEMATODE/spiral_nematode.htm), and ring nematodes are strictly ectoparasites; root-knot, lance (http://entnemdept.ufl.edu/creatures/nematode/lance_nematode.htm), and lesion (http://entnemdept.ufl.edu/Creatures/NEMATODE/amaryllis_nematode.htm) nematodes are endoparasites. In Florida, the most common nematodes causing damage to athletic field turf are sting, lance, root-knot, and stubby-root nematodes.

Figure 2. 

Size comparison of a typical plant-parasitic nematode to a cotton thread.


[Click thumbnail to enlarge.]

Figure 3. 

A typical plant-parasitic nematode stylet resembles a hypodermic needle.


[Click thumbnail to enlarge.]

Figure 4. 

An ectoparasitic nematode feeding by inserting its stylet into a root tip.


[Click thumbnail to enlarge.]

Figure 5. 

Endoparastic nematodes burrowing within a root.


[Click thumbnail to enlarge.]

How do nematodes damage athletic turf?

As plant-parasitic nematodes feed, they damage the root system and reduce the ability of the grass to obtain water and nutrients from the soil. Roots may be abnormally short and appear darkened or rotten when damaged by plant-parasitic nematodes (Figure 6). Often the roots will appear “cropped off” an inch or so below the soil surface (Figure 7). Root galls or knots associated with certain nematode damage to other crops are often not evident on grasses.

Figure 6. 

Healthy grass roots (left) and dark, rotting grass roots damaged by nematodes.


[Click thumbnail to enlarge.]

Figure 7. 

Healthy bermudagrass roots (right) and roots that have been cropped off at about 1/2 inch deep by nematodes (left).


[Click thumbnail to enlarge.]

When nematode population densities get high, and/or when environmental stresses such as high temperatures or drought occur, aboveground symptoms may become evident. Symptoms include yellowing, wilting, browning, or thinning out. Grass will die under extreme nematode and environmental stress. Often, as the grass thins out, spurge and other weeds may become prominent (Figure 8). Nematode damage usually occurs in irregularly shaped, declining areas that may enlarge slowly over time (Figure 9). Nematode symptoms on turfgrasses can be very similar to other factors, such as localized soil conditions, fungal diseases, or insects, and are easy to misdiagnose.

Figure 8. 

In this athletic field infested with sting nematodes, turf declines and weeds proliferate.


[Click thumbnail to enlarge.]

Figure 9. 

Nematode damage results in irregular-shaped patches of wilting, thinning turf.


[Click thumbnail to enlarge.]

Nematode-damaged athletic fields require more frequent irrigation and fertilizer and herbicide inputs than healthy turf. Additional risk to players may result from plant-parasitic nematodes. This is because the nematode-damaged turf does not have a good root system to anchor it down. When athletes are pushing or make sudden turns, the turf can pull up and lead to knee and ankle injuries.

How do I know if nematodes are a problem?

With any plant problem, an accurate diagnosis is important to address the problem and to avoid wasting time, money, effort, and unnecessary pesticide applications. The only reliable way to determine if plant-parasitic nematodes are involved in a grass problem is by having a professional nematode diagnostic lab conduct a nematode assay. The University of Florida has such a facility and will assay nematode samples for $20 each (out-of-state samples cost $25 each). Forms and instructions for submitting nematode samples to the Florida Nematode Assay Lab can be downloaded at http://nematology.ifas.ufl.edu/assaylab.

A nematode assay is a separate procedure and requires different sampling guidelines than those required for soil analysis or disease samples. Be aware that when a disease sample is submitted to most labs, a nematode analysis is not normally performed unless you specifically request it. A nematode assay often requires separate payment and may even be sent to a separate address. Familiarize yourself with the procedures required by the lab where you intend to submit the sample. The accuracy of the diagnosis depends on the quality of the sample that you submit. Following the guidelines below will help ensure an accurate diagnosis:

  1. A sample must consist of multiple soil cores. Nematodes are not evenly distributed in soil, but rather congregate in “hot spots.” Nematode populations may be high at one spot and low just a few feet way. By collecting multiple cores with a device such as a “T” type soil sample tube, an average population density can be measured. A good rule of thumb is to have 16 to 20 cores per field. Cores should be taken to a depth of 4 inches.

  2. If damage is evident, then sample near the margin of the affected area (Figure 10). Nematode populations will decline in severely damaged areas because they have nothing left to eat. Therefore, populations tend to be highest near the edges of a declining area where the grass is still alive. If damage is occurring in a number of areas in one field, take a few cores from the border of several affected areas to make the 20 cores. When taking samples from turf that is not showing symptoms, or if sampling before planting, sample in a “zig-zag” pattern across the area (Figure 11).

  3. Put the soil from each sampled area into a plastic bag and seal it. Nematodes require moisture to survive, so drying the soil will kill them. This is different than submitting a sample for nutrient analysis, where dry soil is preferred. Make sure that each bag is labeled with a permanent marker so that the diagnosis can be assigned to the correct area. If using a self-sealing bag, seal it with tape also because the zippers often come open in transit.

  4. Handle samples carefully. Do not expose samples to direct sunlight or heat. Nematodes are sensitive to high temperatures and UV light. Leaving samples on the dashboard or in the back of a pickup truck can kill them quickly and negatively affect the accuracy of the diagnosis. Keeping the nematode sample in a cooler is best. The nematodes will be sandwiched between soil particles, so rough handling will destroy them. For shipping and transport, pack the samples well to minimize shifting.

  5. Submit the sample right away. Next-day delivery is best. One study found greatest nematode recovery from hand-delivered samples, the next highest from next-day delivery, and the lowest from regular postal delivery.

Figure 10. 

Collect cores for a nematode sample from the edges of declining areas.


[Click thumbnail to enlarge.]

Figure 11. 

When sampling healthy-appearing turf, collect cores in a zig-zag pattern across the area.


[Click thumbnail to enlarge.]

The staff at the University of Florida Nematode Assay Lab will make a determination on whether or not nematodes are a problem based on which nematodes are found and how many of them there are. Not all plant-parasitic nematodes are equal in their ability to harm grass. For example, one sting nematode can cause damage equal to hundreds of individuals of some other types of plant-parasitic nematodes. The number of each type of nematode in 100 cc of soil from the sample that you submit will be used to determine the risk level for the turf species indicated. The risk level will tell you if the turf is at low, moderate, or high risk of damage from plant-parasitic nematodes. Be aware that different diagnostic labs may use different extraction techniques, different quantities of soil, or different thresholds. Because of this, samples submitted to separate labs may report different quantities of nematodes. Do not be alarmed by this: In most cases the different thresholds used are adjusted to account for the differences in methodology and local conditions. However, if you are using a lab in distant locations, your local conditions or regional variations in nematode aggressiveness may not be taken into account. Often your local labs will provide the most accurate assessments.

How do I manage nematodes?

Before Planting

Use Clean Sod: It is always preferable to avoid a potential problem than to deal with an existing one, so it is best to consider nematodes before planting or replanting. The first consideration, especially for an area that has had nematode problems in the past, is grass selection. Not all nematodes are equally damaging on all grasses. Contaminated planting material (sod or sprigs) is a means whereby nematodes can be spread into new areas. It may be worthwhile to have potential sod tested for the presence of large numbers of the more damaging turf nematodes (sting and lance nematodes) before purchase. Growing sod on soilless media offers the best chance of avoiding nematodes but is beyond the budget of most athletic facilities and parks.

Tolerant Grasses: Not all turfgrass species and cultivars are equally affected by nematodes, so grass selection can be important if nematodes are a major concern. Generally, bahiagrass is the most tolerant of all turfgrasses to nematodes and is a good choice for chronically affected areas. Seashore paspalum is more tolerant of sting nematode than bermudagrass but is more susceptible to damage from spiral nematodes. University of Florida research has found that the bermudagrass cultivars 'Celebration', and 'Princess 77' were the bermudagrass cultivars used in Florida with the greatest tolerance to sting nematode. This does not mean that those cultivars were not damaged by the nematodes, but that they were damaged less than was the conventional cultivar.

Cultural Practices

Turf can often exist with a given population density of plant-parasitic nematodes with no visible damage. Damage usually becomes evident when one of two things occur: 1) some other factor increases the susceptibility of the grass to nematode damage and/or 2) some factor causes nematode population densities to increase to damaging levels. Once the grass is planted, the best way to reduce the likelihood of nematode damage is to minimize these factors as much as possible.

Mowing: Generally speaking, the lower the grass is mowed the greater the stress the grass is under. Often raising mowing height slightly can reduce nematode damage considerably. Infrequent mowing should be avoided. The more foliage is removed at each mowing, the greater the stress that is put on the grass.

Fertilizing: Excessive nitrogen fertilization can increase succulent root growth and encourage rapid foliage growth. Succulent root tips are more susceptible to nematode damage, and the proliferation of root tips (nematode food) can cause nematode population densities to rise dramatically. Rapidly growing foliage drains nutrient reserves from the roots that are needed to compensate for the nematode damage. Underfertilization should also be avoided. Roots damaged by nematodes already have a reduced capability to extract nutrients from soil. This makes nutrient deficiencies more pronounced on nematode-infested plants.

Irrigation: Deep, infrequent watering encourages deep root growth. A deep root system is more tolerant of nematodes than a shallow root system resulting from shallow, frequent watering. However, once nematode damage is extensive, frequent watering may be required to keep the grass from declining. In this case, water should be applied as often as permitted by ordinance to avoid wilting.

Aeration: Overcompaction reduces oxygen penetration to the root system and enhances susceptibility to nematode damage. Regular aeration encourages a healthy root system and thereby enhances tolerance to nematodes.

Soil Amendments: Generally, anything that promotes healthy root growth can enhance tolerance to nematodes. Incorporation of colloidal phosphate has been shown to enhance bermudagrass tolerance to several nematodes. Some organic amendments, such as composted municipal sludge or composted manures, may also reduce nematode damage and speed the recovery process after damage has occurred.

Shade: By damaging roots, nematodes impair the ability of turf to store energy. Therefore, nematode-damaged turf often is more prone to decline from shade or prolonged poor weather. If areas are in partial shade, trimming or thinning trees to get more light to the turf will greatly enhance the turf’s ability to withstand nematode damage.

Overseeding: UF research has shown that overseeding can increase nematode numbers on bermudagrass during transition by providing an alternate food source to the nematodes during the winter. Therefore, it is best to avoid overseeding when possible from a nematode management standpoint.

Pesticides and Biopesticides

Even the best-managed turf can suffer from nematode injury. In order to kill nematodes in soil, nematicides are toxic at low levels and are water soluble so that they can be moved into the ground with irrigation water. Many of the effective nematicides used in the past have been withdrawn from the market during the last 25 years for environmental and health reasons. The pesticide options below are ones that are currently available and have shown efficacy in UF research trials. None of the products below are known to have systemic activity and therefore are more effective against ectoparasites like sting or spiral nematodes than endoparasites like lance or root-knot nematodes.

Curfew Soil Fumigant: Curfew Soil Fumigant is labeled for nematode control on athletic fields in Florida and other coastal states in the Southeast. This pesticide is very effective against ectoparasitic nematodes and certain other turfgrass pests like mole crickets. Curfew Soil Fumigant can be applied only by an approved commercial applicator using specialized application equipment. The fumigant is injected as a liquid 5 to 6 inches deep in the soil using tractor-mounted slit-injection equipment (Figure 12). After injection, the active ingredient moves through the soil as a gas and kills nematodes upon contact. Curfew Soil Fumigant cannot be used in areas with karst geological features, and buffer and reentry restrictions apply.

Nortica: The active ingredient in Nortica is the bacterium Bacillus firmus strain I-1582. This bacterium colonizes the root system of the turf and produces compounds that protect the root system from nematodes. Nortica is a wetable granule or powder that dissolves fully in water. It is sprayed onto the turf surface and then moved into the soil with irrigation. University of Florida research has shown this bionematicide to be effective in protecting turfgrass roots from nematode damage when it is applied properly. However, timing is critical with this product to achieve good results. An application schedule map for Florida counties is available from Bayer Environmental Sciences that should be consulted when scheduling applications.

The University of Florida is committed to bringing you the most current information possible. Consequently, this document will be modified with each breaking development. The most current version of this document may be obtained online at the University of Florida’s Electronic Document Information System (EDIS) website at http://edis.ifas.ufl.edu/.

For additional information regarding nematodes, nematode management, or help interpreting nematode assay results, contact:

William T. (Billy) Crow, Ph.D.

Associate Professor of Nematology

University of Florida Entomology and Nematology Dept.

P.O. Box 110620

Gainesville, FL 32611

(352) 273-3941

FAX (352) 392-0190

E-mail wtcr@ufl.edu

http://entnemdept.ufl.edu/lab/people/crow/

For information on submitting samples to the University of Florida Nematode Assay Lab or to check on the status of a sample you submitted, contact:

Nematode Assay Lab

Building 970, Natural Area Dr.

P.O. Box 110620

Gainesville, FL 32611

(352) 392-1994

FAX (352) 392-0190

E-mail nemalab@ifas.ufl.edu

http://nematology.ifas.ufl.edu/assaylab/

Tables

Table 1. 

Risk Levels for Warm-Season Turfgrasses Used by the University of Florida Nematode Assay Laboratory

Nematode Species

Bermuda

Zoysia

Seashore paspalum

St. Augustine

Centipede

 

M

H

M

H

M

H

M

H

M

H

Root-knot

(Meloidogyne)

80

300

80

300

80

300

80

300

80

300

Sting

(Belonolaimus)

10

25

10

25

10

25

25

50

10

25

Lance

(Hoplolaimus)

40

120

40

120

40

120

40

120

40

120

Stubby-root

(Paratrichodorus)

150

300

150

300

150

300

40

120

150

300

Stubby-root

(Trichodorus)

40

120

40

120

40

120

40

120

40

120

Spiral

(Helicotylendhus)

700

1500

700

1500

700

1500

700

1500

700

1500

Spiral

(Peltamigratus)

150

300

150

300

150

300

150

300

150

300

Ring

(Mesocriconema)

500

1000

500

1000

500

1000

500

1000

150

300

Sheath

(Hemicycliophora)

150

300

150

300

150

300

150

300

150

300

Sheathoid

(Hemicriconemoides)

500

1000

500

1000

500

1000

500

1000

150

300

Awl

(Dolichodorus)

10

25

10

25

10

25

10

25

10

25

Cyst

(Heterodera)

---

---

---

---

---

---

10

40

---

---

Key:

--- = not believed to cause significant damage .

M = Turf is considered at moderate risk of damage. Damage may become evident if the turf is placed under stress conditions.

H = Turf is considered at high risk of damage. Root systems are likely damaged and turf quality may be declining.

* These risk levels are based upon numbers per 100 cc of soil extracted using a sugar-flotation with centrifugation method.

** While bahiagrass is a host for many of these nematodes, it is very tolerant to them and seldom is damaged. Therefore, no risk levels are given.

*** Other nematodes such as dagger, lesion, stunt, etc. may damage turf in Florida, but damage from these is very rare so risk levels are not listed.

**** These risk levels are based upon nematodes, grasses, and conditions in Florida only. They may not apply in other states.

Footnotes

1.

This document is ENY-038 (IN126), one of a series of the Entomology & Nematology Department, UF/IFAS Extension. First published: March 2001. Revised Febuary 2013 and January 2014. For more publications related to horticulture/agriculture, please visit the EDIS website at http://edis.ifas.ufl.edu/.

2.

William T. Crow, associate professor, Entomology & Nematology Department, UF/IFAS Extension, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.