A PRACTICAL RESEARCH DIGEST FOR TURF MANAGERS

Volume 10, Issue 12 • December 2001 0

DISEASE CONTROL IN THIS ISSUE "7 •Root-knot on Root-knot nematodes on turf in the northeastern turf in the northeastern United States 1 Biology

United States Distribution

By Nathaniel Mitkowski, Ph.D. Damage and symptoms

Control or many years, nematodes were not considered to cause significant disease on golf courses, particularly in the Northeast. While there are many reasons for this, manage- Hopes for the future Fment techniques, the subtle nature of most damage (especially in northern climates) and the difficulty in researching nematode problems on a perennial host claim •Mechanical maintenance of most of the responsibility for this gap in understanding (Nelson, 1995). bowling greens 5 It is now known that nematodes can cause significant damage on many turf grasses. How- Late winter/early spring ever, the diagnosis of nematode symptoms is still difficult and control of these plant pathogens can be time consuming, expensive and inconvenient. Spring While there are many species of nematodes that attack grasses, I have a particular interest in Meloidogyne graminis, a root-knot nematode. While seen infrequently in the past, it seems The bowling season to be increasing in its incidence, an observation based on turf samples submitted to the Uni- Autumn renovation versity of Rhode Island Turf Diagnos- tic Lab and the Plant Disease Clinic at Autumn/winter ABSTRACT the University of Massachusetts . Unlike fungi, many nematode pop- •Do "low drift" nozzles work Root-knot nematodes (Meloidogyne graminis) are ulations develop relatively slowly and — an update 10 gradually becoming more prevalent on golf courses damage may only be observed during How about pest control? throughout New England. These nematodes can be periods of high stress. In Rhode Island, particularly damaging to turf, as a result of their inti- levels of Meloidogyne graminis are still Results from recent studies mate relationship with plant hosts. Symptomology relatively low and this particular nema- • From the editor. 15 is general in nature and difficult to diagnose. tode is only found sporadically. How- Typically, these and other nematodes are considered ever, these unique organisms can be I should know better... stress related diseases. Only through soil sampling difficult to manage when encountered and extractions can identification be made conclu- and can develop very high populations sively. Many grass species have been reported as in turf. For these reasons, it is worth being susceptible and no genetic resistance effective examining the management and con- against Meloidogyne graminis has been identified. trol of these organisms. Control of these organisms can be a perennial problem and Nemacur is the only chemical regis- Biology tered for use on golf courses with nematode prob- Root-knot nematodes (Meloidogyne lems. Timing of application is also critical for efficacy spp.) are distributed widely through- against root-knot nematodes. out the United States and can cause significant damage on a wide variety ¡DISEASE CONTROL TURFGRASS TRENDS

Executive Editor Sue Porter 440/891-2729; 440/891-2675 (fax) of plant species (Goodey et al., 1965; Wal- Distribution sporter@advanstar. com ters and Barker, 1994). They are generally Although there are over fifty recognized Managing Editor recognized as one of the most destructive of species of Meloidogyne, only two are regu- Curt Hurler the plant-parasitic nematodes because of larly found in the Northeast: Meloidogyne 440/238-4556; 440/238-4116 [email protected] the intimate relationship they establish hapla and Meloidogyne graminis. For the most part, root-knot nematodes are tropical On Line Editor with their plant hosts. Lynne Brakeman While the great majority of plant-parasitic to subtropical organisms.

Senior Science Editor nematodes spend their lives in the soil, prob- While growers, horticulturalists and super- Dr. Karl Danneberger ing into plant roots with their stylet and mov- intendents in warmer climates have to con- Group Editor ing about multiple feeding sites, root-knot tend with numerous root-knot nematodes, Vern Henry nematodes enter into plant roots and perma- temperate winters are an impedance to most Production Manager nently set up camp. They inject molecules Meloidogyne species and a large number of Rene' Fall 218/723-9352; 218/723-9223 (fax) into plant cells which cause dramatic other nematodes (Van Gundy, 1985). In rfall@advanstar. com changes in plant physiology effectively addition, southern root-knot nematodes tend Senior Graphic Designer hijacking the roots (Dropkin, 1989; de to be more aggressive and have a shorter life- Laura Watilo Blake Guiran and Ritter, 1979; McClure, 1977). cycle (and thus more generations) than 440/891-2713; 440/891-2675 (fax) lblake@advanstar. com To feed the nematode continuously, northern root-knot nematodes. plants respond by forming "giant cells" Root-knot nematodes generally have very Circulation Manager Cheryl Beeman (Endo, 1971). Acting as large sinks, these wide host ranges, making it difficult to identi- 218/723-9271; 218/723-9433 (fax) cells draw in nutrients from the surround- fy non-host crops or resistant germplasm. cbeeman@advanstar. com ing area and funnel them to the nematode. However, the presence of only these two root- Group Publisher The nematode con- knot nematodes in the John D. Payne 440/891-2786; 440/891-2675 (fax) tinues to develop as Northeast does pro- jpayne@advanstar. com the plant roots are vide some reprieve. Corporate & Editorial Office altered and eventual- Golf course superin- 7500 Old Oak Blvd. ly the swollen female tendents also have an Cleveland, OH 44130-3369 and the giant cells additional advantage: Mew Subscriptions 888/527-7008 form the characteris- Meloidogyne hapla tic gall or knot, which (which causes signifi- Abstracts: 800/466-8443 cant losses on onions, Reprint: 440/891-2744 gives the nematode Permission: 440/891-2742 its name. carrots and other veg- Single copy or back issues: Eggs are produced Symptoms of a highly virulent isolate etables) will not repro- Subscription/Customer Service 888/527-7008; (fax) 218/723-9437 throughout the lifes- of Meloidogyne hapla infecting lettuce. duce on grasses (Wid- Web site address: pan of the female and mer et al., 1999). www.landscapemanagement.net are either deposited into the surrounding Conversely, however, Meloidogyne graminis soil or remain embedded in the root tissue. will reproduce on nothing but grasses (Mac- w Often they can be seen appearing to adhere Gowan, 1984). ADVANSTAR to the gall as egg masses. COMMUNICATIONS In terms of reproductive capacity, no Damage and symptoms Chairman and other nematode comes close. While the In order to understand the type of damage Chief Executive Officer number of eggs produced by a single root- root-knot nematodes can cause, it is neces- Robert L. Krakoff knot nematode can vary widely, popula- sary to consider their mode of parasitism. Vice Chairman & CTO James M. Alic tions of nematodes can often average any- When manipulating plant roots into generat- where from 500 to 2,000 eggs per female. ing giant cells, the stele or vascular system of President & COO Joe Loggia Millions of nematodes can be produced on the plant is being usurped. Nematode feed-

VP-Finance, CFO & Secretary a single plant. The lifecycle of root-knot ing is focused upon the xylem parenchyma David W. Montgomery nematodes is highly dependent upon soil (Dropkin, 1989). The ultimate result is a Executive Vice Presidents temperatures, but in the Northeast, the considerable disruption in the water and Alexander S. DeBarr lifecycle can be as short as three weeks. nutrient uptake of infected plants. Daniel M. Phillips Thus, there is a significant potential for Symptoms are generally consistent with Executive Vice President - this type of damage. On very hot days, Corporate Development large numbers of nematodes to be pro- Eric I. Lisman duced in a single season. especially when minimal amounts of water

Treasurer and Controller Adele D. Hartwick have been applied, plants will wilt easily. There is currently only Symptoms can also be very general, such as one nematicide registered for a reduction in vigor, chlorosis and plant use on golf course greens stunting. Because of reduced nutrient which will work against root- uptake, nematode damage may mimic knot nematodes, Nemacur. nutrient deficiencies which will not respond While Nemacur can be to fertilizer applications. extremely effective, it is In southern states, however, Meloidogy- highly toxic to people and ne graminis can cause very dramatic symp- has a 24 REI. Consequently, toms. On St. Augustine grass, the nematode greens to which it has been may outright kill grass in large patches applied must be temporarily (MacGowan, 1984). shut down. And unfortu- Typical galls of Meloidogyne graminis, The majority of nematodes can only be nately, Nemacur will not produced on wheat. Galls produced by diagnosed through soil sampling. Nematodes eliminate the problem, only this nematode are more delicate and rela- are microscopic organisms and in order to reduce the number of nema- tively cyclindrical, as compared to those confirm their presence they must be extract- todes in the soil. caused by M. hapla. ed from the soil and observed under the Areas with chronic prob- microscope. Because root-knot nematodes lems will require multiple cause such dramatic symptoms on host applications of the pesticide. plants, however, root galling can sometimes While it has yet to be reported be used to diagnose them. The disadvantage in the Northeast, in the South, to identifying root-knot nematodes solely on increased biodégradation of the basis of root galling is that galling occurs Nemacur has been observed three to four weeks after infection. If a visu- under high application rates. al inspection of the roots is made prior to this Soils repeatedly treated with time, galls will not be observed and the the pesticide will develop nematodes will escape detection. populations of microorgan- In addition, galls on grass roots are com- isms capable of degrading the A low level of Meloidogyne graminis monly very small and difficult to see. For pesticide and thus limiting its infection on wheat, indicated by sparse these reasons, it is best to sample for root-knot usefulness. This type of "resis- galling. Galls are commonly observed as nematodes as if they were any other nema- tance" to a chemical is biolog- slight swellings on turfgrass roots and fre- tode, by taking a minimum of five to ten one- ically very different from typ- quently are not even observed. inch cores per green (spread across each ical fungal resistance to green) and forwarding them to your local turf pesticides, but is functionally similar. diagnostic lab or nematode diagnostic lab. Another option exercised by superinten- Processing of soil samples for nematode diag- dents is fumigation. While only practical nosis is a relatively time consuming effort during renovations, this option may have however, so be cognizant of the costs involved severe consequences in the future. When in having many greens diagnosed. fumigation is utilized, the majority of soil- borne organisms are killed, not only plant- Control parasitic nematodes. Controlling Meloidogyne graminis can be From a short-term perspective, this very difficult. Nematode eggs will remain will remedy the problem. However, if in plant roots or in the soil throughout the plant-parasitic nematodes are reintro- winter. When spring arrives, nematodes will duced (which is not uncommon), they hatch and penetrate plant roots near the may cause more problems than before area of cell elongation. fumigation. This is because the act of Once feeding has been initiated, chemi- fumigating the soil has removed all of the cal controls will have very little effect. native antagonists of the plant-parasitic Therefore, the critical time for application nematodes. While it is unclear how much of nematicides is in the spring, before nema- control antagonists exercise over plant- todes have entered the roots. parasitic nematodes, it is possible that Cultural they may be able to keep populations could be developed into commercial vari- below damage threshold levels in some eties and be easily over seeded into estab- practices can instances. lished turf stands. In addition, there are alleviate When fields are fumigated in prepara- many golf courses where the levels of plant- tion for high value annual crops, the same parasitic nematodes remain well below some of the cycle will occur. However, because these damage thresholds. The reason for this is damage crops are harvested every year, fumigation not well understood. can be undertaken every few years, a luxu- Investigations into the effect of golf caused by ry golf course superintendents do not have. course management and microbial com- root-knot Cultural practices can alleviate some of munities on plant-parasitic nematodes may the damage caused by root-knot nematodes, lend some insight into useful management nematodes, but generally these practices are inconsis- practices. tent with the demands of players. Simply but generally Nathaniel Mitkowski received his B.S. from the put, grass that is under minimal stress will Department of Plant Pathology at the these still support populations of plant-parasitic University of Massachusetts in 1997. It was practices are nematodes but will be less likely to show here that he got his first exposure to turf symptoms. This means raising the height of pathology, as a student of Dr. Gail Schumann. inconsistent cut and limiting the amount of play, options He received his Ph.D. from the Department of with the which are generally not feasible. Plant Pathology at Cornell University in 2001. There, his research focused on nematode dis- demands Hopes for the future eases of vegetable crops, particularly of players. One of the research aspects I hope to focus Meloidogyne hapla. He was recently hired by on in the future will be to examine the genet- the University of Rhode Island as an Assistant Professor to fulfill the role of Turf and ics and pathogenicity of Meloidogyne Ornamentals Pathologist. Beginning in 2002 graminis. The ultimate goal of this research he will oversee the direction of the URI Turf will be to identify techniques to manage this Diagnostic Laboratory. and other plant-parasitic nematodes on turf using strategies other than chemical controls. One method that may show promise is the use of resistant germplasm, which

LITERATURE CITED de Guiran, G. and M. Ritter. W.F. Mai, and R.A. Rohde, eds. McClure, M.A. 1977. Walters, S.A. and K.R. Barker 1979. Life cycle of Academic Press; New York. : a 1994. Current distribution of Meloidogyne species and 347 p. metabolic sink. Journal of five major Meloidogyne species factors influencing their devel- Nematology 9:88-90. in the United States. Plant Goodey, J.B., M.T. Franklin and opment In: Root-knot nema- Disease 78(8):772-774. D.J. Hooper. 1965. The nema- Nelson, E.B. 1995. Nematode todes (Meloidogyne species). tode parasites of plants cata- disorders of turfgrass, how Academic Press, New York. p. loged under their hosts. important are they? Turfgrass Widmer, T.L., J.L. Ludwig and 173-191. Farnham Royal, Bucks, Trends 4(10): 1-16 G.S.Abawi. 1999. The Dropkin, V.H. 1989. England. northern root-knot nematode Van Gundy, S.D. 1985. Introduction to Plant on carrot, lettuce, and onion in MacGowan, J.B. 1984. Ecology of Meloidogyne spp. - Nematology. Wiley and Sons, New York. New York State Meloidogyne graminis, a root- emphasis on environmental New York. p. 158-168. Agricultural Experiment Station factors affecting survival and knot nematode of grass. Bulletin 156. New York State pathogenicity. In: An Endo, B.Y. 1971. Nematode- Nematology Circular No. 107. College of Agriculture and Life Advanced Treatise on induced syncytia (giant cells). Florida Department of Science, Cornell University. Host-parasite relationship of Agriculture and Consumer Meloidogyne. Volume I: Heteroderidae. Pp. 91-117 in: Services. Division of Plant Biology and Control. Ed. J.N. Plant Parasitic Nematodes. Industry. Sasser and C.C. Carter. NCSU Volume II. B.M. Zuckerman, Graphics, p. 177-182.