Nematodes areunsegmented round-worms. Most are micro-scopic. All nematodes areaquatic animals, and soilnematodes live in the thinfilms of water surrounding soilparticles. Not all soil nema-todes damage turf; in fact, mostare beneficial and help cycle car-bon and nitrogen in the soilenvironment. However, plant-parasitic nematodes feed onliving plant tissue and canharm turfgrass.

A typical plant-parasiticnematode is equipped with ahollow stylet or mouth spear.The stylet resembles a hypoder-mic needle, and has a similar func-tion. The nematode inserts itsstylet into the root cells of a plantand injects digestive enzymesthrough it. The nematode thenuses the stylet like a straw toremove the partially digested cellcontents. The digestive secretionsinjected by different nematodes havedifferent effects on roots. This is onereason why some plant-parasitic nema-todes cause more damage than others.

Symptoms of NematodeDamage to Turf

The damage nematodes cause to turf grasses isdifficult to distinguish from the damage causedby water stress, nutrient deficiency or root dis-

eases. Turf may turn yellow and/or wilt dur-ing the heat of the day because the dam-

aged root systems cannot supply ade-quate nutrients and water to theplant. The turf may become thin,which often allows weeds to grow inaffected areas. In severe cases, theturf may turn brown and die. Rootsmay have swellings, lesions, or astubby appearance, or appear dark

or undeveloped.

Nematodes are not evenly dis-tributed in the soil, but congre-

gate in “hot spots.”Population densities

may be veryhigh in one

area, andlow justa fewfeet

away.Because

of thisuneven dis-

tribution,nematode dam-

age usually occursin patches rather

than uniformly acrossan area. Nematode damage is more

evident on greens than fairways becausegreens are more intensively managed, are mowedat lower heights, and have more traffic, all ofwhich puts the grass under greater stress.

Because nematode damage my be indistin-guishable from other problems, diagnosis shouldnot be based on symptoms alone. Proper diagno-sis of a nematode problem can be made only bymeans of a soil test.

L-53513-00

*Extension Plant Pathologist, The Texas A&MUniversity System.

Nematodesin

Texas GolfCourses

William Crow*

Testing for NematodesThe first step in managing nematodes is to

properly identify the problem. This should bedone by a credible diagnostic lab. Different diag-nostic labs process the samples differently and,therefore, the number of nematodes recoveredcan vary from lab to lab. However, each lab usesthresholds developed for its extraction method,so the final recommendations (whether or not totreat) shouldn’t vary.

Soil testing for nematodes is different from soilnutrient testing, so the sampling procedure is alsodifferent. The accuracy of the test results dependson the quality of the sample, so the soil must becollected and handled correctly.

Because nematodes are not evenly distributedin the soil, a sample must consist of multiplecores. If there are no above-ground damage symp-toms, take at least 20 cores from random loca-tions across the sample area (Fig. 1). If symptomsare visible, take at least 20 cores from the marginsof the affected area (Fig. 2). Nematodes feed onliving tissue, so the highest populations of nema-todes will be near the edges of affected areas, notwhere the plant damage is most severe.

The best tool for taking a nematode sample is a3/4-inch-diameter “T” type sampling tube (Fig. 3).Take the cores to a depth of 2 to 3 inches, wheremost of the plant roots are located. Deeper sam-pling will lower the quality of the sample.

Place all the cores into a single plastic bag andseal it tightly. Do not use a paper bag. Nematodesrequire moisture to live, and if the soil sampledries out the diagnosis will not be accurate.Remove the sample from direct sunlight as soonas possible and store it in a cool place, but do notlet it freeze. Soil in plastic bags can heat up rapid-ly and heat kills nematodes. Handle the soil sam-

ple gently; the nematodes are sandwichedbetween soil particles and rough handling willdestroy them.

Deliver the sample to a diagnostic lab as soonas possible. Studies show that more nematodesare recovered from hand-delivered samples thanfrom mailed samples. If you must mail the sam-ple, place it in an insulated container, pack it wellto prevent shifting, and send it by overnight mail.

With your sample, provide as much informa-tion as possible about the symptoms you’veobserved and the history of plantings in the areasampled. If pesticides have been applied recently,the lab must be notified. Pesticide residues can bedangerous to the diagnostician who processes thesample.

The test results you receive will indicate thegenera and densities of nematodes recovered inyour sample, and the lab will recommend treat-ment for particular species if warranted. Thethreshold population densities labs use to makesuch recommendations are rough estimates only.But nematode population isn’t the only factorthat affects the amount of damage they cause.Other factors are the variety of grass, environ-mental stresses (temperature, watering, mowingheight, etc.), and the interactions between differ-

Figure 1. This sting nematode (Belonolaimus longicau-datus) is feeding on a root tip.

Texas A&M University has an excellent nema-tode diagnostic facility and will process soil samples for a charge of $20 each. Submissionforms can be obtained from your countyExtension office, from the Web(http://plantpathology.tamu.edu/index4.html), or ordered from the following address:

Texas Plant Disease Diagnostic LaboratoryTexas A&M University Research Park1500 Research ParkwayCollege Station, Texas 77845

ent types of nematodes and between nematodesand other pathogens.

Most of the research that established thresholdpopulations was done on Bermuda and St.Augustine grasses. The same thresholds are usedfor other turf grasses such as bentgrass and zoysia.More research is needed to establish thresholdsfor these grasses and for various environmentalconditions.

Which Nematodes Affect Turf?There are many types of plant-parasitic nema-

todes that damage turf grasses. With certainspecies, relatively few nematodes can cause agreat deal of damage, whereas with other species,a much greater number is required to cause anyvisible damage. Most nematodes remain in thesoil and insert only their stylets into the root(ectoparasites). Some enter the root and remainthere (endoparasites). Still others enter the rootwith only part of their body (semi-endoparasites).

The following species may be reported on diag-nostic test results and are listed in order of theirability to damage turf grasses.

Sting nematode (Belonolaimus longicau-datus): This is probably the most damagingnematode to turf grasses (Fig. 4). Relatively fewsting nematodes can devastate a root system.They are ectoparasites and thrive in soil withmore than 80 percent sand content. USGA speci-fications for putting green construction require

90 percent sand content in the root zone mixture,an ideal habitat for the sting nematode.

Awl nematodes (Dolichodorus ssp.): Awlnematodes are rare in Texas, but are as damagingas sting nematodes. Awl nematodes are usuallyfound only in moist soil near ponds or ditches,and are ectoparasitic.

Lance nematodes (Hoplolaimus ssp.):Lance nematodes also can be very damaging toturf grasses. They are more common in Texas thansting nematodes, and are more common in soilswith a higher silt and clay content than are stingnematodes. The lance nematode is a semi-endoparasite.

Stubby root nematodes (Paratrichodorusspp., Trichodorus ssp.): These ectoparasitic nema-todes are frequently detected in Texas turf sam-ples, and are considered damaging to turf grasses.

Root-knot nematodes (Meloidogyne spp.):With these endoparasites, the adults remain with-in roots and only juveniles are detected in soilsamples. This makes it difficult to estimate popu-lation densities from soil analysis. Therefore, theamount of damage they cause is not well known.

Ring nematodes (Mesocriconema andrelated genera): These ectoparasites are the mostfrequently detected nematodes in Texas turf sam-ples, but they are considered damaging onlywhen very high numbers are present. Centipedegrass is the most susceptible to damage from ringnematodes.

Non-diseased grass

Diseased grass

Dead grass

Correct sample location

Figure 3. When collecting soil samples from turf thathas no visible symptoms, take at least 20 cores in azig-zag pattern as shown.

Figure 2. When collecting soil samples from turf thatshows symptoms of nematode damage, take at least20 cores from near the margins of the affected area.

Lesion nematodes (Pratylenchus ssp.):These common nematodes are generally consid-ered only moderately damaging to grasses; how-ever, their effects have not been thoroughlystudied. They are endoparasites.

Others. Other nematodes found in Texas golfcourses include spiral (Helicotylenchus andrelated genera), stunt (Tylenchorhynchus andrelated genera), sheath (Hemicycliophora ssp.),sheathoid (Hemicriconemoides ssp.), and pin(Paratylenchus spp.) nematodes. These nema-todes may cause damage when their numbers arehigh.

ManagementDuring construction or reconstruction of

greens, soil can be treated with one of severalfumigant nematicides to reduce nematode popu-lations before planting. While methyl bromidewas commonly used in the past to disinfect soilfrom nematodes, weeds, insects and diseases, thischemical is being phased out because of itsozone-depleting properties. Other fumigantnematicides currently labeled for use in greenconstruction and reconstruction include:

dasomet (Basamid®); 1,3-dichloropropene

(Telone® products); and metam-sodium (severalbrand names). Be careful not to use nematode-infested sod. It is advisable to have the sod testedbefore planting.

If treatment is recommended for establishedturf on commercial golf courses, there are severalnematicides labeled for use in Texas. Some of themore common and effective of these are

fenamiphos (Nemacur® products), ethoprop

(Chipco Mocap®), and 1,3-dichloropropene

(Curfew®). Nematicides with a systemic mode ofaction are more effective against endoparasticnematodes within plant roots then are someother products. Be aware that not all nematicideslabeled for turf have been consistently effectivein university trials. Carefully follow directionson the product label to ensure safety and to pre-vent phytotoxicity.

Because the effects of nematodes can be ampli-fied when grass is under stress, manage infestedturf to minimize stress by raising the mowingheight, applying adequate fertilizer, and wateringdeeply to encourage deep rooting.

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Educational programs of the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion,age or national origin.

Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amend-ed, and June 30, 1914, in cooperation with the United States Department of Agriculture. Chester P. Fehlis, Deputy Director, TexasAgricultural Extension Service, The Texas A&M University System.

1M, New PP

Figure 4. A “T” type soil sampling probe is the besttool for collecting nematode samples.

The information given herein is for educational purposes only. Reference to trade names is made with the understanding that no dis-crimination is intended and no endorsement by the Texas Agricultural Extension Service is implied.