Volume 8, Number 4

TUR FAX July-August 2000 of the International Sports Turf Institute, Inc. The International Newsletter about Current Developments in Turfgrass

IN THIS ISSUE and perennial ryegrasses (L. perenne), and tall fes- cue (F. arundinacea). The pathogen also causes blast, The Nature of Gray Leaf Spot and Its Manage- the most important disease of rice (Oryza sativa) world- ment wide. Is My Annual Bluegrass () a Peren- nial, Annual, or Something Else? History of gray leaf spot on turfgrasses JB Comments: The Diversity in Evapotranspi- ration Rates of Turfgrasses Gray leaf spot was formally reported causing seri- Research Summary: Seeded and Vegetatively ous blighting of perennial ryegrass fairways on two golf Propogated Cultivar Comparisons within both courses in southeastern Pennsylvania in 1991 Cynodon and Species (Landschoot and Hoy land, 1992). It appeared in late China Discovers Benefits of Turfgrasses August/early September, coinciding with unseasonably Rutstroemia floccosum warm temperatures and high relative humidity. In 1995, Ask Dr. Beard gray leaf spot reached epidemic proportions in pe- rennial ryegrass grown on golf courses in the Mid- Atlantic regions. The disease was most severe in southeastern Pennsylvania, Delaware, and non-moun- tainous areas of Maryland, Virginia, and Kentucky. In The Nature of Gray Leaf Spot Maryland, the disease was first observed in 1986 on a and Its Management golf course near Annapolis. Between 1986 and 1994, the Maryland disease diagnostic lab received only a few samples of perennial ryegrass affected with the disease. Peter H. Dernoeden The disease, however, was probably causing low lev- els of injury in roughs on numerous golf courses for ray leaf spot is caused by the Pyricularia years, resulting in a gradual buildup of inoculum. Evi- Ggrisea and is a common disease of St. Augustine- dently, environmental conditions in 1995 were ideal grass (Stenotaphrum secundatum) lawns in the south- for disease development and the inoculum had by this eastern United States. It can be particularly damaging time reached sufficient levels on many golf courses to to newly sprigged lawns, but may be a chronic prob- initiate the epidemic. The 1995 summer was among lem in mature stands of St. Augustinegrass grown in the warmest and driest of the century in the Mid-Atlan- subtropical climates. Bermudagrasses (Cynodon spp.), tic region, suggesting that heat and low soil moisture centipedegrass (Eremochloa ophiuroides), fescues levels were important predisposing conditions. In 1996, (Festuca spp.), bentgrasses ( spp.), Kentucky the disease recurred, but was not as widespread as in bluegrass (), and ryegrasses (Lolium spp.) 1995, and most injury occurred in roughs and green are listed as species susceptible to gray leaf spot. Some surrounds. The 1996 summer, however, was among the of the aforementioned turfgrass species only were coolest and wettest in the prior 50 years. The ability of shown to be blighted by P. grisea in growth chamber the pathogen to cause significant levels of injury in two studies. In the field, however, there is only good docu- very different summer environments suggested that in- mentation that the pathogen inflicts significant dam- oculum levels were sufficient to ensure that the disease age to St. Augustinegrass, annual (L. multiflorium) would be a recurring problem in the region. By 1998, ...Gray Leaf Spot... Continued from page 1

however, the disease had moved out of the Mid-At- ity intensifies with increasing temperature, but high lantic region and was observed as far north as Rhode humidity at night or long leaf-wetness durations are Island and Iowa, and as far west as Nebraska, Kan- essential for disease development. sas, and Oklahoma. The summer of 1998 was warm, not hot, but it was very dry. The summer of 1999 was Symptoms and signs of gray leaf spot in peren- among the driest ever recorded in many regions of the nial ryegrass golf turf USA, and gray leaf spot pressure was low. According Working with both perennial and annual ryegrasses, to Dr. Waker Uddin (personal communication) of Penn Trevathan et al. (1994) found that seedlings were killed State University, the night-time relative humidity lev- by P. grisea, but mature plants only developed leaf spot els critical for gray leaf spot development were too low lesions, and sometimes leaves were blighted. and conditions were too dry in the summer of 1999 for Landschoot and Hoyland (1992) also observed seed- an epidemic to occur. ling death, but on mature plants P. grisea primarily The cause of the rapid spread of the disease is un- caused leaf spotting and perennial ryegrass crowns gen- known. There are no reports of the disease in the Pa- erally were unaffected. As noted in several texts, gray cific Northwest, where most perennial ryegrass seed is leaf spot in perennial ryegrass historically was regarded grown. Therefore, there is no evidence that the patho- as a seedling, damping-off disease. It was widely be- gen is being spread by seed. Dr. Mark Farman (Per- lieved that mature plants generally survived infection sonal communication) of the University of Kentucky by P. grisea. The epidemic of 1995, however, revealed has found that the biotype of P. grisea that attacks pe- that the pathogen was extremely virulent and could rennial ryegrass is different from that which attacks rice. kill large areas of turf in a few days. The increased Hence, the origin of the pathogen may not have come virulence of P. grisea may have been the result of a from rice-producing areas in the USA, and the primary genetic change in the fungus, resulting in a new bio- source of the inoculum is unknown. The most likely means of spread is by wind dispersal of spores and type or race of the pathogen. by mowers. Indeed, early outbreaks of the disease in The first infected perennial ryegrass plants on golf Louisiana and Mississippi were believed to be due to courses normally appear in Maryland by the third week spores being carried on wind currents by hurricanes. of July, but often develop later in other states. Most Once the pathogen is established at a site, the spores samples typically arrive in our diagnostic lab in Au- are rapidly dispersed by mowing. Dissemination of gust and September. Once blighting develops, the dis- the fungus by golfers dispersing the pathogen in their ease can remain active until the first severe frosts in travels with contaminated golf shoes or clubs also is early November. In general, however, the disease sub- possible. The mechanism by which the pathogen over- sides in October. The fungus produces enormous num- winters is unknown. It is likely, however, that it sur- bers of spores overnight. It initially attacks leaves, and vives as dormant mycelium in dead tissues. within hours leaf tips may appear water-soaked and chlorotic. Thereafter, leaf spot lesions and leaf twist- ing occur. Below the twisted areas, a small number of Predisposing environmental factors leaf lesions are sometimes evident. Frequently, the Most of what is known about the environmental con- youngest emerging leaf is twisted in the shape of a "fish ditions that trigger the disease comes from researchers hook." Plants with the fish hook symptom may not have who studied the disease on St. Augustinegrass, rice, any lesions. This suggests that germinating spores can and tall fescue. To reach epidemic levels, rainy weather penetrate basal leaf sheaths at or below the soil sur- or prolonged periods of high humidity and tempera- face. It also is possible that spores are splashed by rain tures above 70°F are required. Uddin et al. (1998) re- or irrigation, and are carried by water into the leaf ported that gray leaf spot in tall fescue was favored sheaths. Spores can be disseminated rapidly by mow- most by leaf wetness durations of 36 to 40 hours at ing, resulting in a streaking pattern similar to that asso- 80°F (27°C) or 16 to 40 hours of leaf wetness at 83°F ciated with Pythium blight. Evidently, within a very (28°C). The disease, however, could develop in tall fes- few hours the spores germinate, penetrate cut leaf cue after only 8 hours of leaf wetness at temperatures wounds, and begin to cause blight before the leaves above 76°F (24°C). Dr. Uddin (personal communica- dry in the morning. tion) recently has learned that the fungus requires fre- The leaf lesions are generally circular to oblong, quent cycles of leaf wetting and drying in order for about 1/8 to 1/4 in. (2-6 jnm) long and grayish-brown spore production to become prolific. Disease sever- Is My Annual Bluegrass (Poa annua) a Perennial, Annual, or Something Else?

Fred Yelverton nity to use a preemergence herbicide prior to an- nual bluegrass seed germination. Contrary to popu- he annual biotype of annual bluegrass (Poa annua) lar belief, many herbicides provide very good control Tand the perennial biotype, Poa annua var. reptans, of the annual biotype if applied and activated (wa- are the most troublesome weeds on golf courses in the tered-in) prior to annual bluegrass seed germination. world. These weeds infest many other highly main- Most of the preemergence herbicides used for crab- tained turfgrass areas, such as home lawns, sports fields, grass (Digitaria spp.) and goosegrass (Elusine indica) etc. From a management standpoint, it is appropriate control are effective for control of the annual types of to think of annual bluegrass as a group of weeds rather Poa annua. Premergence herbicides are not effec- than an individual species. This is because there is a tive for controlling the perennial Poa annua types great deal of variation within the Poa annua species. because it does not have to come back from seed. There are true annual types and true perennial types, With perennial types, you always have a mixture of but to add to the confusion there are many intermedi- plants of different age growing simultaneously. ate biotypes that can act as either perennials or annu- The important question to address for management als, depending on environmental conditions. of annual types of Poa annua is when does it germi- As a general rule, the warmer the climate, the nate? Annual bluegrass can germinate over a wide greater the proportion of the annual bluegrass popu- range of environmental conditions. And this is prob- lation that will be annuals. Conversely, cooler cli- ably the most important reason why annual bluegrass mates tend to have more perennial types. This is because is so prevalent in turfgrasses. In warmer climates, the annual bluegrass species does not have a great deal where the annual types are more common, previ- of heat tolerance. In transitional areas, there are annual ous research has shown that germination can oc- and perennial biotypes growing side by side. In addi- cur throughout the winter. However, research has tion, perennial types tend to survive better under very also shown that a majority of the annual types ger- high maintenance, such as putting greens, because of minate in the autumn. This may sound confusing water and fungicide inputs. because annual bluegrass is not obvious until the So how do turfgrass managers determine whether spring, when seedheads start to form, or in the winter you have the annual or perennial type? One question to where warm-season turfgrasses go dormant. In addi- ask is, does the annual bluegrass at your site survive tion, small annual bluegrass plants are very difficult the summer? If it does, then the type you have is acting to see because the seedling is tiny and seed germina- as a perennial. If your annual bluegrass has an explo- tion usually occurs when the turfgrass species is ac- sion of seedheads in the spring and the plant cannot be tively growing or at least has not gone dormant. seen in the summer, then most likely you have the an- Consider the following data from a research trial nual type. The fact that the plant cannot be seen in sum- conducted at North Carolina State University. This trial mer is not an absolute determination of the annual type was conducted to help determine the ideal application because the plant can go dormant in summer and reap- time for preemergence herbicides for control of the pear when weather conditions become more favorable annual types of Poa annua. Many herbicides were used in autumn. Many perennial weeds go dormant in either in this trial, but only oxadiazon (Ronstar®) at 2 lbs winter or summer, depending on species. a.i./ac is shown here. This is because oxadiazon is a Why is it important to know whether you have the true preemergence herbicide. If any annual bluegrass perennial or annual biotype? From a turfgrass man- seed has germinated, oxadiazon will not provide con- agement standpoint, this is the critical question. This trol. Note that mid-August and mid-September ap- is because the annual type is much easier to con- plications provided excellent control, but trol with herbicides than the perennial type. Be- applications after mid-September provided very cause the annual type must come back from seed poor control. This is because between mid-Septem- every year, turfgrass managers have the opportu- ber and mid-October, a large flush of annual bluegrass Continued on page 4 3 ...Annual Bluegrass... Continued from page 3 seed germination occurred. We also can interpret these Comparative Timings of Herbicide Application for data to say that only about 20-25% of the annual blue- Annual Bluegrass Control. North Carolina State grass seed germinated after mid-October while the re- University, Raleigh, NC. 1996-97. mainder germinated prior to mid-October. Application Date Percent Control * Of course, we have to keep in mind that these dates apply for this particular site and other areas with a similar August 13 91 climate. In addition, yearly variations in weather con- September 12 99 ditions at this site may produce different results in other October 11 21 years. But the point is that annual types of Poa annua November 13 24 germinate early in the autumn and a majority of germi- * Percent control ratings were recorded April 25 of nation occurs in the autumn for many climates. ^ the following spring.

...Gray Leaf Spot.. Continued from page 2

with a dark brown border. Gray or brown lesions solani). Large areas of turf may collapse in 3 to 5 days. with or without a dark brown border frequently develop Under less favorable environmental conditions, large along the edges or margins of leaf blades. A yellow pockets of dead turf may require a 3- to 4-week period halo occasionally can be observed bordering lesions. to develop. Infected stands often develop a bluish-gray Lesions, however, may be the size of a pinhead and hue, which is typical of drought stress symptoms. very dark brown. These lesions are similar to those Hence, perennial ryegrass in roughs or fairways that caused by the net blotch pathogen, Drechslera appear wilted in the presence of good soil moisture is a dictyoides. Net blotch, however, generally is associ- good indicator of gray leaf spot. The disease is most ated with extended periods of overcast and rainy severe in heat-sink areas, such as south-facing hillsides weather of spring. Because leaf spotting pathogens such and knolls. To date, the disease has been restricted to as D. dictyoides, Bipolaris sorokinana, and Curvularia perennial ryegrass, while creeping bentgrass (A. spp. can cause leaf lesions and leaf twisting that mimic stolonifera), annual (P. annua), rough (P. trivialis) and P. griseay disease diagnoses based on leaf lesions in Kentucky bluegrass, fescues, and bermudagrasses grow- the field are difficult. ing in severely damaged perennial ryegrass fairways In the early morning hours the twisted leaf tips and roughs have been unaffected. of lesions on the margins of leaves may appear felted, Another feature of the disease was that it generally and infected tissues may be gray, dark brown, begins and is more destructive in golf course roughs, purple, or yellow. The felted appearance is the result particularly the intermediate rough where the soil of the production of huge numbers of spores and their was compacted by cart traffic. Evidently, the higher spot-bearing stalks known as conidiophores. The most canopy in the rough provides a more favorable microen- effective means of positively diagnosing gray leaf vironment for the pathogen. This is supported by the spot is to microscopically confirm the presence of observation that the disease is generally less severe in the spores. low-cut perennial ryegrass approaches and collars. From a standing position, the first observable symptom is the appearance of reddish brown or gray Cultural management colored spots 1 to 2 in. (2-5 cm) in diameter, which could easily be confused with Pythium blight or dollar Research conducted by Vaiciunas and Clarke (1998) spot, respectively. There is, however, no foliar myce- showed that gray leaf spot was less severe as mow- lium associated with gray leaf spot. During prolonged ing height was reduced from 3.5 to 0.5 in. (7.6-1.5 hot, humid, and dry weather the dead spots of turf en- cm) during low disease pressure periods. Under high large to 3 to 18 in. (8^-6 cm) in diameter. At this point disease pressure, however, mowing height did not im- disease symptoms mimic brown patch (Rhizoctonia pact disease severity. They also found that nitrogen ...Gray Leaf Spot... Continued from page 4

(N) fertilization reduced disease severity when epi- ing resistance to gray leaf spot on golf courses. Creep- demics developed in the autumn. However, when ing bentgrass, bermudagrass and Japanese zoysiagrass the epidemic began earlier in the summer, applications (Zoysia japonica) are all good fairway species. Choice of nitrogen at rates exceeding 1.5 lb N/1,000 ft2 (75 kg of species is dependent on the climatic region. N/ha), applied in 0.5 lb N/1,000 ft2 (25 kg N/ha) in- crements on a 28-day interval, intensified the disease. Chemical control They reported a benefit from removal of clippings, but only when disease pressure was low. Earlier re- Where the disease is chronic, preventive appli- search conducted in St. Augustinegrass also showed cations of fungicide appear to be the best approach that clippings removal reduced disease severity (Parris, to controlling gray leaf spot. Once the disease de- 1971). The effect of herbicides and plant growth regu- velops, higher rates and more frequent fungicide lators on the incidence and severity of gray leaf spot is applications are required. Daconil® (chlorothalonil) unknown. Some management practices that may help is effective. However, even high rates are not likely to to reduce gray leaf spot severity would include: re- provide more than 5 to 10 days of control. Daconil® is duce mowing height; avoid mowing when leaves are a contact fungicide and as such the effectiveness of wet; collect clippings; apply small amounts of nitro- the material is diminished by removing the fungicide gen fertilizer at 0.1 to 0.125 lb N/1,000 ft2 (5-6 kg N/ during routine mowing and probably by the effects of ha) in spoon-feeding programs during the summer; and UV light and other factors. Fungicides that penetrate maintain adequate soil moisture levels by irrigating tissues provide a longer residual, but commercially during daytime hours. acceptable levels of control may be provided for only Observations by Turner in 1997 indicated that some 10 to 21 days, depending on the product and rate ap- perennial ryegrass cultivars showed good gray leaf spot plied. Compass® (trifloxystrobin) and Heritage® resistance during a moderate disease pressure summer (azoxystrobin) are very effective, particularly at the in Maryland (1998 NTEP Prograss Report). However, high label use rate. Spectro® (a pre-packaged mixture during a high disease pressure period in 1998, all culti- of chlorothalonil + thiophanate), CL 3336® and Fungo vars in the Maryland study were damaged severely by 50® (thiophanate), and Lynx® (terbuconazole, not yet the disease. Germplasm screening programs con- registered) also have very good activity. CL 3336® ducted at Rutgers University and elsewhere have and Spectro® provide 10 to 14 days control at higher shown that there is no genetic resistance to P. grisea label rates. Banner® (propiconazol) and Bayleton® among all commercially available perennial ryegrass (triadimefon) alone are not very effective, but when cultivars. tank-mixed with Daconil® they also provide 10 to 14 Severely damaged fairways overseeded in late July days of control during high pressure epidemics. In or August often do not tiller or establish good density curative programs, however, all of the aforementioned or quality play ability because of high temperature stress. fungicides should be tank-mixed with Daconil®. Fun- During renovation, seed must make contact with soil. gicides like Chipco 26GT® (iprodione) and ProStar® This is best achieved using a slicer seeder. Broadcasted (flutalonil) have no activity against gray leaf spot. seed does not establish well because the seed is either There is no doubt that the pathogen has become well directly attacked or very young seedlings are killed as established, and gray leaf spot will be a potential they emerge. Seedlings will be attacked by P. grisea, problem in perennial ryegrass grown on golf courses and possibly R. solani and Pythium spp. Hence, tank- from the Great Plains states to the Atlantic sea- mixes of a broad spectrum fungicide with a Pythium- board. Along with golf courses, perennial ryegrass targeted material need to be applied to seedlings. Low grown on athletic fields and lawns also is vulnerable to rate, weekly sprays of a water-soluble nitrogen source, the disease. Where gray leaf spot is known to be like urea at 0.1 to 0.125 lb N/1,000 ft2 (5-6 kg N/ha), chronic, fungicide applications should begin in early and syringing 2 to 3 times daily also help to improve to mid-July. As previously noted, however, the disease seedling vigor. often begins in August or September in many regions. In extreme cases, renovation to a resistant spe- Hence, you need to know when the disease develops cies may become necessary. While creeping bentgrass, in your region to properly time the first spray. Field bermudagrass, and Kentucky bluegrass are reported observations indicate that the disease is best man- hosts, all of these grasses have thus far shown outstand- aged before any blighting becomes evident. Once

Continued on page 6 JB COMMENTS The Diversity in Evapotranspiration Rates of Turfgrasses

here are major differences in the évapotranspira- Relative ET Rate Ttion rates among many turfgrass species, especially Ranking* (mm d"1) Turfgrass under peak environmental conditions, which maximize very-low <6 American buffalograss the évapotranspiration rate. Unfortunately, this water conserving characteristic is not being utilized suffi- low 6-7 **hybrid bermudagrass ciently. Evapotranspiration rate (ET) is the amount centipedegrass of water evaporated from a turf area per unit of time. It **dactylon bermudagrass may be expressed as inches per week (in./wk) or mm/ **zoysiagrasses day (mm/d). The relative maximum évapotranspiration moderate 7-8.5 hard fescue rates of 21 turfgrasses when grown in their respective Chewings fescue climatic regions of adaptation and preferred cultural red fescues regime are shown in the accompanying table. bahiagrass Any cultural and/or environmental factors that alter seashore paspalum the leaf area or shoot density of a given turfgrass spe- St. Augustinegrass cies may result in a significant shift in its relative rank- high 8.5-10 perennial ryegrass ing compared to the other species. Cultural factors that common carpetgrass contribute to an increased évapotranspiration rate include kikuyugrass (a) higher cutting height, (b) higher nitrogen nutritional tropical carpetgrass level, which stimulates the leaf extension rate and re- sultant leaf area, and (c) high to excessive irrigation rate very high >10 tall fescue and/or frequency, which increases the stomatal density creeping bentgrass on leaves. Typically, turfgrass species that have a higher annual bluegrass shoot density, narrower leaf width, and more horizontal *Kentucky bluegrass leaf orientation tend to have a lower évapotranspiration rough bluegrass rate than the more erect, low-density, wide-leafed spe- annual ryegrass cies. The peak ET rates can range from 3 to 12 mm per *Based on the most widely used cultivars of each spe- day among turfgrass species. It should be noted that cer- cies. tain cultivars ranking lower in ET rate can exhibit ET **Significant variability occurs among cultivars within rates in the 1.5 to 2.0 mm per day range under condi- the species. tions of minimal to low evaporative demand.

...Gray Leaf Spot... Continued from page 5 blighting appears, a high rate of Daconil® should be References tank-mixed with one of the aforementioned penetrants. Landschoot, P.J. and B.F. Hoyland. 1992. Gray leaf spot of peren- Affected areas should then be re-treated in 5 to 7 days nial ryegrass turf in Pennsylvania. Plant Dis. 76: 1280-1282. with another application of Daconil®. Thereafter, tank- Parris, G.K. 1971. Practical control of two lawn grass diseases mix combinations will likely be required on 10- to 21- without fungicides by removal of mower clippings. Plant Dis. day intervals, depending on the fungicide, rate applied, Rept. 55: 775-779. and environmental conditions. It is important to use Trevathan, L.E., M.A. Moss, and D. Blasingame. 1994. Ryegrass high water volumes of greater than 50 gallons per acre blast. Plant Dis. 78:113-117. (470 L/ha), and to delay mowing for 24 hours follow- Uddin, W., L.L. Burpee, and K.L. Stevenson. 1997. Influence of temperature and leaf wetness duration on development of gray ing the application. Vigilant scouting for gray leaf leaf spot (blast) of tall fescue. Agronomy Abst. 137-138. spot requires almost daily attention from July Vaiciunas, S. and B.B. Clarke. 1998. Impact of cultural manage- through October. The disease can be very active in ment practices and genotype on development of gray leaf spot September and October, and is especially destructive in cool-season turfgrasses. Agronomy Abst. 140. to new seedlings in overseeded areas previously dam- 1998 Prograss Report of the National Turfgrass Evaluation Pro- aged by gray leaf spot. V gram. Perennial ryegrass trials, USDA, Beltsville, MD 20705. Research Summary Seeded and Vegetatively Propagated Cultivar Comparisons within both Cynodon and Zoysia Species

number of seeded cultivars of bermudagrass quality, shoot density, and leaf blade width. The green- A(

China Discovers Benefits of Turfgrasses

James B Beard system of antagonists to the disease-causing bacte- rial and viral organisms had resulted in a major in- uring the communist purges that occurred through crease in disease-causing organisms, which were Dout China some decades ago, one of the dictates to readily disseminated by the windblown dust par- eliminate capitalist symbols from the country was to ticles. Unfortunately, I never was given the opportu- remove green lawns and even cut down ornamental nity to review the actual documents on which these trees. Subsequently, many of China's outdoor public conclusions were drawn. Similar problems were occur- open spaces have been maintained as well-swept dirt ring in many other large cities in China. ground. The soil has become severely compacted and In an attempt to eliminate these serious urban pollu- is groomed each morning by a large number of broom- tion and human health problems, the Chinese govern- wielding workers. ments in these major urban centers have embarked on a More than 15 years ago I was contacted by Chinese major program to re vegetate the open spaces by plant- government officials concerning the development of a ing turfgrasses in parks, on sports-recreation areas, along revegetation plan for the open spaces in the city of roadsides, and around major government facilities. Even Bejing. The elimination of green vegetative covers that the famous Tiananmen Square now has two distinct stabilize the soil had resulted in a major increase in turfed lawn areas. atmospheric pollution within the city in the form of fly- This series of historical events ranging from the ex- ing dust and even dust storms that reduced visibility. tremes of bare dirt to the use of turfgrasses sends a strong More importantly, increases in a number of serious message. It emphasizes the important values of human diseases were occurring at a much greater rate turfgrasses, not only from an aesthetic standpoint, than in any other major non-Chinese city in the world. but also from the beneficial effects in reducing pol- Their interpretation was that the lack of green veg- lution, protecting human health, and enhancing the etative cover and its associated living biological eco- quality of life in densely populated urban areas. ^ TURFAX™ Rutstroemia floccosum © 2000 Ann Arbor Press Introductory offer: $69.95 + shipping he dollar spot disease of turfgrasses was originally attributed to the and handling Tcausal fungal pathogen homoeocarpa by F.T. Bennett 6 issues/year in England in 1935. During the past decade turfgrass pathologists in the Available by mail and/or fax United States have determined that the causal pathogen is not Sclerotinia homoeocarpa, but have not been able to clarify the specific causal patho- Ann Arbor Press P.O. Box 20 gen. Recently research at the University of Minnesota supported by Chelsea, MI 48118 research at Michigan State University, has proposed that the fun- Telephone: 800-487-2323; gus Rutstroemia floccosum (Powell and Vargas) is the causal patho- 734.475.44il gen in North America. It is a facultative-parasitic, fungal pathogen in Fax: 734-475-8852 the prder and class Discomycetes. Whether this same fungal www.sleepingbearpress.com species is the causal pathogen of dollar spot in the United Kingdom and Europe is yet to be determined. ^

EDITOR Dr. James B Beard ASK DR. BEARD International Sports Turf Institute Inc. 1812 Shadowood College Station, TX 77840 Q What can I do to grow bermudagrass turf in shaded areas?

CONTRIBUTING EDITORS A Bermudagrass (iCynodon spp.) is one of the poorest of the warm- Dr. Peter H. Dernoeden season turfgrasses in terms of adaptation to shaded areas. The Department of Natural Resource high light intensities of full sun induce horizontal growth of the Sciences and Landscape lateral stems of bermudagrasses. Unfortunately, the low light inten- Architecture sities of the shaded environment result in a distinct emergence and University of Maryland upright growth of lateral stems, including both the rhizomes and College Park, MD 20742 stolons of bermudagrass. This distinct upright growth results in a Dr. Daniel A. Potter major percentage of the bermudagrass shoot growth being removed Department of Entomology during mowing. The result is a drastically reduced leaf area and a S-225 Agriculture Science Center, N very thin turf of poor quality for bermudagrass. For the physiologi- University of Kentucky cal reasons just described, all turfgrass cultivars of bermudagrass Lexington, KY 40546 grown for turfgrass purposes have traditionally exhibited very poor shade adaptation, as have Adalayd seashore paspalum Dr. Fred Yelverton (), American buffalograss (Buchloe Department of Crop Science dactyloides), and certain purple-stemmed cultivars of St. Box 7620 North Carolina State University Augustinegrass (Stenotaphrum secundatum). Raleigh, NC 27695 Perhaps a breakthrough has occurred in the recent release of a new bermudagrass cultivar. Specifically, it is named MS- ADVISORY COMMITTEE Choice, which is a Cynodon dactylon released from Mississippi State University by Dr. Jeff Krans and colleagues. It is attributed to Gary Grigg Royal Poinciana Golf Club have enhanced shade tolerance compared to other bermudagrass cultivars. In addition, it forms a very dark-green, compact, leafy, Bruce Williams prostrate turf with very few seedheads. This vegetatively propagated Los Angeles Country Club cultivar is suggested for use on sports fields, golf course tees and Dan Quast fairways, and home lawns with a mowing height that can range from Medinah Country Club 0.5 to 2.0 inches (13-50 mm). An elevated cutting height usually is preferred for shaded turfs.^ Don Tolson Stock Farm Ask Dr. Beard: TURFAX, c/o Ann Arbor Press P.O. Box 20 Gordon Witteveen Chelsea, MI 48 U 8 Board of Trade Country Club Email: [email protected]

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