Nematode Management for Golf Courses in Florida1
Golfing contributes to the quality of life of many residents and visitors to the state of Florida. Some of the criteria that are used to designate a “good” course are speed and evenness of the playing surface, and green, healthy-appearing grass on the greens, tees, and fairways. Each of these quality parameters can be negatively affected by plant-parasitic nematodes (Figure 1). Of all the pests that commonly affect golf course turf in Florida, nematodes are probably the least understood and most difficult to manage. Nematode problems are more common and more severe in Florida than in most other states because our climate and soils provide a perfect habitat for many of the most destructive species.
Diagram of a typical plant-parasitic nematode.
What Are Nematodes?
Nematodes are unsegmented roundworms, different from earthworms and other familiar worms that are segmented (annelids) or in some cases flattened and slimy (flatworms). 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 golf course. 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 a group of nematodes that feed on plants, these are called plant-parasitic nematodes (Figure 1).
Size comparison of a typical plant-parasitic nematode to a cotton thread.
A typical plant-parasitic nematode stylet resembles a hypodermic needle.
Figure 3.
An ectoparasitic nematode feeding by inserting its stylet into a root tip.
Figure 4.
Endoparasitic nematodes burrowing within a root.
How Do Nematodes Affect 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 in a cup-cutter sample (Figure 7). Root galls or knots associated with certain nematode damage to other crops may not be evident on grass.
Healthy grass roots (left) and dark, rotting grass roots damaged by nematodes (right).
When nematode population densities get high enough, or when environmental stresses such as high temperatures or prolonged low light occur, aboveground symptoms may become evident. Symptoms include yellowing, wilting, browning, or thinning out. Often, as the grass thins out weeds, particularly spurge (Figure 8), may become prominent. Grass will die under extreme nematode and environmental stress. Nematode damage usually occurs in irregularly shaped patches that may enlarge slowly over time (Figure 9). Be aware that similar conditions may be caused by other factors such as localized soil conditions, fungal diseases, or insects.
Turf decline caused by nematodes is often accompanied by proliferation of spurge.
Figure 8.
Nematode damage usually occurs in irregular patches.
How Do I Know If Nematodes Are A Problem?
With any plant problem, having an accurate diagnosis is important to address the problem and to avoid wasting 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 nematode assay conducted by a professional nematode diagnostic lab. The Florida Nematode Assay Lab is such a facility and will assay nematode samples for a cost that is currently $20 for each sample from Florida and $25 for each sample from outside of Florida. Nematode sample kits containing everything needed to collect and submit a sample, along with instructions, are available at your local county Cooperative Extension office.
Nematode analysis is a separate procedure and requires different sampling guidelines than those required for soil analysis or plant 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. Nematode analysis 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. If you are taking a sample for submission to another lab, or if you are submitting a sample to the Florida Nematode Assay Lab without using our sample kits, following the guidelines below will help insure an accurate diagnosis:
1.) A sample must consist of multiple cores. Nematodes are not evenly distributed in soil, but are grouped 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 (Figure 10) an average population density can be measured. A cup-cutter core is not an adequate sample for nematode diagnosis, though it may be adequate for a disease diagnosis. A good rule of thumb is to have a minimum of 20 cores per area (green, fairway, etc.). Each core should be taken to a depth of 3 inches.
A "T" type soil sample tube is ideal for collecting nematode samples from turf.
2.) If damage is evident then sample near the margin of the affected area (Figure 11). 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.
Collect cores for a nematode sample from the edges of declining areas.
When taking samples from turf that is not showing symptoms, or if sampling during construction or reconstruction, sample in a “zig-zag” pattern across the area (Figure 12).
When sampling healthy appearing turf collect cores in a zig-zag pattern across the area.
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 golf cart can kill nematodes 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 so that shifting is minimized.
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.
The staff at the 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 (Table 1). 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, use different quantities of soil, or use 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, 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
It is always preferable to avoid a potential problem than to deal with an existing one, so it is best to consider nematodes during course construction or reconstruction. Currently, chemical management of nematodes before planting is achieved by soil fumigation. This involves injecting a liquid or incorporating a granular material into the soil. The material then either coverts to a gas or releases a gas that kills the nematodes. In addition to nematodes, many of the fumigants have activity against weeds and/or soilborne diseases and/or insects. Several soil fumigants are currently available for course construction and reconstruction. For detailed information on soil fumigation see the Florida Cooperative Extension Service document “Soil Fumigation Before Planting Turf” available at your County Cooperative Extension office or on-line at http://edis.ifas.ufl.edu/IN095.
Contaminated planting material (sod or sprigs) are 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.
Established Turf
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 height:
Generally speaking, the lower the mowing height the greater the stress on the grass. This is one reason that nematode damage is often more pronounced on greens than fairways, and nematode damage on roughs is fairly uncommon. Often raising mowing height slightly can reduce nematode damage considerably. One exception to this may be ultra-dwarf bermudas on greens which are better adapted to low mowing.
Fertility:
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.
Under-fertilization should also be avoided. Roots damaged by nematodes will already have a reduced capability to extract nutrients from soil. This makes nutrient deficiencies more pronounced on nematode-infested plants.
Watering:
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 wilting. In this case water should be applied only often enough to avoid wilting and only enough to allow water penetration as deep as the root system.
Compaction and aeration:
Over-compaction reduces oxygen penetration to the root system and enhances susceptibility to nematode damage. 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.
Chemicals
Even the best managed turf can suffer from nematode injury necessitating chemical intervention. In order to kill nematodes in soil most nematicides are toxic at low levels and are water soluble in order to move down to where the nematodes are. 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 until only a handful remain. When using any nematicide the product label must be strictly adhered to in order to minimize human and environmental health impacts and to avoid liability. A list of nematicides labeled for use on golf course turf is given in Table 2. The information in Table 2 is not a substitute for the product label. Always follow directions on the product label when applying any pesticide.
Equipment used for applying Curfew Soil Fumigant to golf course turf.
Figure 13.
Equipment used for applying Turfcure 376 to golf course turf.
Nemacur® products:
There are two formulations of Nemacur® available for use on golf courses, Nemacur® 10G, a granular formulation, and Nemacur® 3 Turf, a liquid formulation. The active ingredient in these products is fenamiphos, an organophoshate pesticide with both contact and systemic activity. Because of its systemic properties it is the only product currently available that can kill nematodes inside of roots. Fenamiphos has been the most commonly used nematicide on golf courses in recent years.
Because fenamiphos has been so widely used without rotation with other products a condition called “enhanced biodegradation” of this compound has occurred on some golf courses in Florida. Fenamiphos is a carbon-containing molecule that can be broken down by microbes in the soil. The more often fenamiphos is used at a given location, the greater the number of these microbes will occur there. These microbe populations can get so high that they become capable of “breaking down” the fenamiphos before it has time to kill the nematodes.
Nemacur is currently under a phase-out and will no longer be produced as of May 2007. However, sales of existing stock may continue through May 2008. Additionally, Nemacur can no longer be used on certain areas defined on the label which states "After May 31, 2005, do not apply to hydrologic soil group A soils that are excessively drained and predominately sand or loamy sand such as soils in the suborder psamments with shallow water tables (less than 50 feet deep). These classifications and soil taxonomy refer to USDA definitions. If you are unsure of the type of soil you are treating, please consult with your county's extension agent or the product manufacturer." See the Bayer Procentral website for more information regarding the phase-out of Nemacur.
Soil fumigants:
Soil fumigants are commonly used to disinfest soil from nematodes and other pests before planting. However, two of them are now being used to manage nematodes on established golf course turf. The fumigants work very differently than other pesticides. Fumigants are injected 6 inches into the soil using a tractor-mounted slit injector (Figure 13 and Figure 14). They are in a liquid state when injected, but turn into a gas in the soil. The gas moves through the soil and kills nematodes on contact. Fumigants require specialized application equipment and training in their use. Therefore, they may only be applied by approved custom applicators. Application of fumigants is an invasive procedure. Occasionally mechanical damage may result from the injection process. However, fumigants can give excellent results.
Equipment used for applying Curfew Soil Fumigant to golf course turf.
Equipment used for applying Turfcure 376 to golf course turf.
Curfew Soil Fumigant: The active ingredient in Curfew Soil Fumigant is 1,3-dichloropropene. This is the same active ingredient that is in the Telone products used by the agriculture market. Curfew has given excellent control of sting and certain other nematodes in University of Florida tests. It also has the added benefit of reducing populations of mole-crickets. Curfew Soil Fumigant now has 24(c) labeling for use on golf course and athletic field turf in Florida, Georgia, South Carolina, North Carolina, Alabama, and Mississippi. According to the product label, Curfew cannot be used on areas with Karst geology (including much of Miami-Dade County). Curfew has a 24 hour reentry restriction as well as a 100 ft. buffer zone to buildings and wells.
Turfcure 376: The active ingredient in Turfcure 376 is metam sodium. This is the same active ingredient that is in Vapam, Busan, and similar products used by the agriculture market. Turfcure 376 has full registration with the EPA. As of the writing of this document Turfcure 376 has a 48 hour reentry restriction and a 50 ft. buffer zone to buildings.Turfcare can be used in some areas of Florida, such as Dade County, where Curfew Soil Fumigant can not be used due to local geological characteristics.
Other products:
The above-mentioned products all have a “Danger” label. This is a concern in a industry such as the golf course industry where there is a high degree of visibility and human involvement. Often considerable pressure is placed on the superintendent by membership who may have founded or unfounded expectations regarding safety or environmental issues. Therefore, a great deal of emphasis is being placed on finding less-toxic nematode control products. Many of these are “biological derivatives” of plants or microorganisms or “biological control” products. Others are non-biological, but are marketed as “non-toxic” or “organic.” These types of products often are safe, but do not need to be proven to be effective to be labeled.
Faculty at the University of Florida are committed to testing as many of these products for efficacy as possible. Additionally, we network with researchers at other institutions to gather their experience with these products. While we have data on many of these products, we do not have data on all of them. Feel free to contact us for information on our experience with specific products.
Summary
Nematode management on a golf course can be a daunting task. Expectations for a pristine playing surface are high and nematodes are notoriously difficult to control. The best management practices for golf courses with nematode problems are: 1) avoid other stresses on the grass as much as possible, 2) monitor nematode populations by sampling frequently, 3) apply chemicals when needed.
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 at your county Cooperative Extension office, or found on line 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:
Dr. W. T. (Billy) Crow, Landscape Nematologist, Etomology and Nematology Dept., PO Box 110620, Gainesville, FL 32611, (352) 392-1901 ext.138, FAX: (352) 392-0190, E-mail: wtcr@ufl.edu.
For information on submitting samples to the Florida Nematode Assay Lab or to check on the status of a sample you submitted contact:
Mr. Frank Woods, Senior Biologist, Nematode Assay Lab, PO Box 110820, Gainesville, FL 32611, (352) 392-1994, FAX (352) 392-3438, E-mail: nemalab@ifas.ufl.edu.
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 thresholds are given.
*** Other nematodes such as dagger, lesion, stunt, etc. may damage turf in Florida, but damage from these is very rare so thresholds are not listed.
**** These thresholds are based upon nematodes, grasses, and conditions in Florida only. They may not apply in other states.
Table 2.Nematicides for use on golf course turf in Florida.
Product
Legal sites, application notes
Rates
Nemacur 10G Restricted use Pesticide. Golf courses and sod farms only; do not use on lawns or public areas other than golf courses. Irrigate immediately after application with at least 1/2 inch of water; do not allow puddling or run-off to occur. Do not treat newly-seeded areas until plants have developed secondary root systems. Do not apply a total of more than 200 lb/acre/year. Do not apply to more than 10 acres per golf course per day; wait 3 days before treating any additional area. After May 31, 2005, do not apply to hydrologic soil group A soils that are excessively drained and predominately sand or loamy sand such as soils in the suborder psamments with shallow water tables (less than 50 feet deep).
2.3 lb/1000 sq ft, or 100 lb/acre Nemacur 3 Restricted use Pesticide. Golf courses and sod farms only; do not use on lawns or public areas other than golf courses. Apply in a minimum of 0.5 gallon of water per 1000 sq ft (approx. 20 gallons per acre). Irrigate immediately after treatment with a minimum of 1/2 inch of water; do not allow puddling or run-off to occur. Do not treat newly seeded areas until plants have developed secondary root systems. Do not use more than twice per year. Do not apply to more than 10 acres per golf course per day; wait 3 days before treating any additional area. After May 31, 2005, do not apply to hydrologic soil group A soils that are excessively drained and predominately sand or loamy sand such as soils in the suborder psamments with shallow water tables (less than 50 feet deep).
9.7 fl oz/1000 sq ft, or 3.3 gal/acre Curfew Soil Fumigant
For use on golf courses and athletic fields. Must be applied by an approved custom applicator. Do not apply within 100 ft. of buildings or wells. 24 hour reentry restriction. Cannot be used on areas with Karst geology.
5 gal/acre
Turfcure 376 For use on fairways, driving ranges and roughs. Must be applied by an approved custom applicator. Do not apply within 50 ft. of buildings. 48 hour reentry restriction.
5 gal/acre
Footnotes
This document is ENY-008 (IN124), one of a series of the Entomology & Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: February 2001. Revised: March 2007. For more publications related to horticulture/agriculture, please visit the EDIS Website at http://edis.ifas.ufl.edu/.
William T. Crow, assistant professor, Entomology & Nematology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.
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contact your county Cooperative Extension service.
U.S. Department of Agriculture, Cooperative Extension Service,
University of Florida, IFAS, Florida A. & M. University Cooperative
Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer, Interim Dean.
