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© 2009 Plant Management Network. Effect of Nozzle Type and Water Volume on Dollar Spot Control in Greens-Height Creeping Bentgrass Megan M. Kennelly, Assistant Professor, Department of Plant Pathology, and Robert E. Wolf, Associate Professor, Department of Biological & Agricultural Engineering, Kansas State University, Manhattan, KS 66506 Corresponding author: Megan M. Kennelly. kennelly@ksu.edu Kennelly, M. M., and Wolf, R. E. 2009. Effect of nozzle type and water volume on dollar spot control in greens-height creeping bentgrass. Online. Applied Turfgrass Science doi:10.1094/ATS-2009-0921-01-RS. Abstract A field study was conducted in 2007 and 2008 to determine the influence of nozzle type and water volume on the control of dollar spot of greens-height creeping bentgrass, caused by Sclerotinia homoeocarpa F. T. Bennett. The nozzles utilized were XR, TurfJet, Air Induction, Turbo TwinJet, and Turbo Drop Twin Fan, all producing flat spray patterns. For each nozzle type, three flow rates were used to produce water carrier volumes equivalent to 0.5, 1.0, or 2.0 gal/1000 ft². Chlorothalonil (1.8 oz/1000 ft²) was applied on a 14-day interval. Disease was assessed by counting the number of dollar spot infection centers in plot centers where spray coverage was complete. Overall, all nozzles except for TurfJet provided similar dollar spot suppression, and water volume was rarely a factor. On one rating date in 2007, all nozzle-volume combinations reduced dollar spot compared to untreated turf except for the TurfJet nozzles at the lower water volumes. On one date in 2008, all nozzle and volume combinations reduced dollar spot compared to untreated turf, with the exception of plots receiving fungicide through XR and TurfJet nozzles at 0.5 gal/1000 ft² or Air Induction nozzles at 1.0 gal/1000 ft². Therefore, the use of a reduced water volume and an air induction drift reducing nozzle may be a practical option for managing dollar spot with a contact fungicide in creeping bentgrass. Introduction Dollar spot is a common disease in creeping bentgrass (Agrostis stolonifera L.) putting greens and fairways (1,14). When creeping bentgrass is mowed at typical putting green heights (0.10 to 0.18 inch), dollar spot causes tan, sunken infection centers with diameters of approximately 1 to 2 inches (1,14). Superintendents apply fungicides on a regular basis to control dollar spot, and it has been reported that more money is spent on fungicides for this disease than any other that occurs in turf (16). There are a number of options for nozzle selection for turfgrass applications. Nozzles vary in droplet size produced, spray pattern, and capacity or flow rate (often expressed as gallons per minute) (13). Equipment manufacturers have attempted to design nozzles which prevent drift but inadvertently may result in reduced coverage. For example, pre-orifice nozzles are designed to reduce internal pressure of the nozzle, thus reducing the exit pressure and therefore the number of small droplets (20). Another drift reduction design is based on a venturi system. A venturi design in a nozzle is a narrowed passageway through the interior of the nozzle that changes the speed of the liquid flow. As the liquid flow passes through the venturi, the flow rate increases creating a vacuum thus allowing air to be drawn into the nozzle chamber through small air inlets. Nozzles with this design are often referred to as air-induction, air-injection, or more appropriately venturi nozzles. The introduced air in the nozzle combines with the spray solution in a mixing chamber, forming "bubbles" which exit the nozzle as large, drift-resistant spray droplets that break into smaller drops upon impact with the plant surface (20). The efficacy of fungicides on turfgrass diseases can be influenced by nozzle selection. Vincelli and Dixon (17) found that nozzles that provided nearly complete coverage provided better dollar spot control in both fairway- and greens-height creeping bentgrass than low-drift nozzles with less-complete coverage. Similarly, chlorothalonil applied in a spray volume of 1.0 gal/1000 ft² and delivered from nozzles producing coarse or extremely coarse droplets provided only moderate or poor dollar spot control in fairway-height creeping bentgrass compared to nozzles with smaller droplets and presumably more complete foliar coverage (3,4,5,7). Along with nozzle selection, spray volume (the amount of water carrier used) is another variable in fungicide applications. Couch (1) reported an optimum spray volume of 1.0 gal/1000 ft² for chlorothalonil for dollar spot and other diseases in green and fairway height turf. In fairway height creeping bentgrass, McDonald et al. (11) observed that chlorothalonil provided better dollar spot control when applied in 1.1 vs 2.5 gal of water per 1000 ft². In the same study, dollar spot control provided by propiconazole, a systemic fungicide, or a mixture of propiconazole and chlorothalonil, did not differ between the two volumes. In another study on fairway height creeping bentgrass, there were no differences in dollar spot control between 1.1 or 2.5 gal/1000 ft² when chlorothalonil was applied in combination with triadimefon, another systemic fungicide (10). While these studies provide insight into dollar spot control, there is a lack of information on the effect of spray volume in combination with different nozzle types. Spray technology for turfgrass applications, however, has received some recent attention in research (3,4,5,6,8,17) and trade (13,18) publications. However, there is still a need for more information. For example, Fidanza et al. (2) found that 68% of superintendents used the same nozzle for all applications, regardless of the target pest or disease, and 41% used the same spray volume for all applications. In this study, our objective was to test the efficacy of a contact fungicide (chlorothalonil) using five nozzle types at each of three water application volumes for dollar spot control on greens-height creeping bentgrass. Description of Field Plots The experiment was performed in 2007 and again in 2008 on two separate stands of creeping bentgrass ‘A4’ on sand-based putting greens at the Rocky Ford Turfgrass Research Center, Manhattan, KS. The two putting greens have a history of natural dollar spot infestation. The turfgrass was mowed 6 days per week to a height of 0.156 inch using a triplex reel mower (The Toro Company, Bloomington MN), irrigated daily for 15 min, and fertilized biweekly with 0.5 lb N per 1000 ft² during March-June and 0.33 lb N per 1000 ft² during July-November. The experiment was set up as a randomized complete block design with four replications. Individual plots were 5 × 5 ft in 2007 and 5 × 6 ft in 2008. Nozzles, Fungicide Rates, Coverage Tests, and Application Timing The nozzle types included were: extended range flat-fan (XR11002, XR11004, and XR11008), TurfJet (1/4TTJ02, 1/4TTJ04, and 1/4TTJ08), Air Induction (AI11002, AI11004, and AI11008), Turbo TwinJet (TTJ-60 11002, TTJ-60 10004), and Turbo Drop Twin Fan (TDTF02, TDTF04, and TDTF08). The Turbo TwinJet is not available in 08 orifice size, and therefore a Turbo Duo adapted with two Turbo TwinJet 04 nozzles (TT11004) orifices was substituted. The Turbo Drop Twin Fan nozzle is distributed by Greenleaf Technologies (Covington, LA) and all other nozzles are distributed by Spraying Systems Co. (Wheaton, IL). The TurfJet nozzle produces coarse droplet sizes and was selected to provide incomplete coverage. The XR is commonly thought to provide complete coverage and thus was selected as the comparison standard for the trial. The Air Induction nozzle is a popular nozzle for drift control and was included to learn about its efficacy at different water carrier volumes. The other two nozzles were twin fan style nozzles, one with a preorifice and chamber design (TTJ-60) and the other (TurboDrop Twin Fan, TDTF) is an air induction design. Both of these nozzles are recent designs and have not been tested for disease control in turfgrass systems. The twin nozzle types are commonly thought to provide better coverage when used in agronomic crops. However, Wolf and Daggaputi (21) reported that single outlet nozzles tended to have better lower canopy coverage in dense soybean when compared to twin nozzle designs. For each nozzle type, three flow rates were used to produce water volumes equivalent to 0.5, 1.0, or 2.0 gal/1000 ft². The nozzle types, orifice sizes, and water volumes are listed in Table 1. For each nozzle type, three flow rates were used to produce water volumes equivalent to 0.5, 1.0, or 2.0 gal/1000 ft². The nozzle types, orifice sizes, and water volumes are listed in Table 1. Table 1. Nozzle types and spray volumes tested in 2007 and 2008 for dollar spot control using chlorothalonil.
w Turbo TwinJet not available in 08 orifice size. Turbo Duo with two TT11004 orifices was substituted to obtain 08 (0.8 gal/min) flow rate. x The last two digits indicate the flow rate per nozzle, in GPM = gallons per minute, i.e., 02 = 0.2 GPM at 40 PSI. y Spray droplet classification based on ASABE Standard 572.1 – Spray Nozzle Classification by Droplet Size (extra fine, very fine, fine, medium, coarse, very coarse, extremely coarse, and ultra coarse). z Coverage data represents the average of six 1 × 3-inch papers. The 0.5 gal/1000 ft² data is based on the DropletScan computer program. The program does not effectively report data when coverage exceeds 60%. Therefore, coverage data for 1.0 and 2.0 gal/1000 ft² water rates is based on a visual estimation of percent coverage and statistics were not performed. Means for the 0.5 gal/1000 ft² water rate followed followed by the same letter are not significantly different according to Tukey’s pairwise comparisons (family error rate P = 0.05). A contact fungicide, chlorothalonil (Daconil Ultrex 82.5WDG, Syngenta Professional Products, Greensboro, NC), was applied at 14-day intervals at a rate of 1.8 oz/1000 ft², corresponding to the lowest label rate for a 7 to 21-day spray interval for preventative control. The low rate was selected to try to maximize the disease pressure and therefore highlight treatment differences that might not be apparent at higher rates. The spray boom held two nozzles 19 inches apart. Application speed (2.7 MPH) and nozzle pressure (40 PSI) were constant for all treatments. Adjustments in the application volume were accomplished by altering the nozzle orifice size for each nozzle type. The boom height during application was approximately 19 inches. In Kansas, dollar spot is often active in spring and early summer, almost nonexistent in mid- to late-summer, and prevalent again in autumn. The 2007 field experiment was planned for the autumn epidemic. In 2007, dollar spot was present in June, completely disappeared in July, and reappeared in August. The 2007 trial was conducted starting in mid-August, with applications on 14 and 27 August and 11 September. Dew was removed by dragging a broom across the plots prior to the fungicide application. In 2008, the study was carried out during the spring/early summer epidemic. Treatments were applied on 13 and 28 May, 10 and 25 June, and 10 July 2008. The turf was mowed immediately prior to the spray, at 0.15 inch, removing dew. Spray coverage was determined by applying water as indicated above, and placing six 1 × 3-inch water sensitive papers (Spraying Systems Co., Wheaton, IL) across the center of the spray pattern. Water sensitive papers are often used as an indicator for the presence of spray deposition (9). Water in the spray stains the paper thus facilitating the evaluation of various droplet characteristics, such as spot size and percent area covered (15). Coverage was analyzed using DropletScan (WRK of Arkansas and Oklahoma, and Devore Systems Inc., Manhattan, KS), a software program coupled with a flatbed scanner that has been designed to analyze spray droplet data collected on water sensitive paper (19). Spray coverage was compared using Tukey’s pairwise comparisons, with a family error rate of P = 0.05 (Minitab 15 Statistical Software, State College, PA). Disease Assessments and Analysis Disease was assessed every 10 to 20 days by counting the number of dollar spot infection centers (DSIC) in a 19 × 19-inch (2007) or 19 × 38-inch (2008) area in the exact center of each plot, where the spray patterns from the two nozzles completely overlapped. Prior to analysis, count data were transformed by taking the square root to stabilize the variance and normalize the data (12). The mean number of DSIC/ft² was compared using Tukey’s pairwise comparisons with a family error rate of P = 0.05 (Minitab 15 Statistical Software, State College, PA). Influence of Nozzle Type and Water Volume Spray coverage. In the applications on water sensitive paper, only the 0.5 gal/1000 ft² water volume could be analyzed (Table 1) because the DropletScan program does not effectively report data when coverage exceeds 60%. Therefore, a visual estimate of percent coverage at the 1.0 and 2.0 gal/1000 ft² rates is reported but not statistically analyzed (Table 1). At 0.5 gal/1000 ft² the TurfJet nozzles had the lowest coverage, with less than half the coverage of all other nozzles (Fig. 1, Table 1). The XR flat-fan nozzles had the highest level of coverage, at 58.3%, though it was not statistically different from the Air Induction, Turbo TwinJet, and TurboDrop Twin Fan nozzles which all provided 40 to 50% coverage. Though Vincelli and Dixon (17) did not provide coverage data for all nozzles, approximately 80% coverage was noted for XR11004 nozzles used at 35 psi and 1.5 gal/1000 ft². Our results are similar, with an estimated 83 to 98% coverage at 1 to 2 gal/1000ft².
The TurfJet nozzles tended to create fewer, larger, blotches of color on the water sensitive paper while the XR and Turbo TwinJet created numerous, finer color spots (Fig. 1). Vincelli and Dixon (17) demonstrated a similar overall pattern for TurfJet and XR nozzles at 1.5 gal/1000 ft². In the present study, the Air Induction and Turbo Drop Twin Fan created a blend of larger and smaller droplets. Future studies should examine the coverage and efficacy of air induction nozzles at higher pressures where drift control would still be retained but coverage might be improved. Though water sensitive paper coverage data can be informative, it is important to be careful when interpreting results. The quality of the spray may be more critical when evaluating efficacy. Nozzles with larger droplets did not provide very uniform coverage. The water sensitive papers utilized were wider than turfgrass blades and therefore may have captured more of the larger droplets than the turfgrass did. In addition, larger droplets could tend to wash off more easily than smaller droplets. Therefore, caution must be used when comparing coverage data on water sensitive paper to actual plants. 2007 dollar spot development. On 26 August there was variation in dollar spot severity, and the untreated plots had the highest disease severity, with 19.5 DSIC/ft², but differences were not significant (Table 2). On 25 September, all nozzle-volume combinations reduced disease compared to the untreated turf, except for the TurfJet nozzles at 0.5 and 1.0 gal/1000 ft² (Table 2). The other four nozzle types performed equally well regardless of spray volume. By the next rating date, 11 October, disease in the untreated plots had declined, and all nozzle-volume combinations provided residual control reducing dollar spot to zero. Table 2. Dollar spot severity as influenced by nozzle type and spray volume, 2007.
x Values represent the mean number of dollar spot infection centers per plot for four replicates. The number of dollar spot infection centers were counted in a 19 × 19-inch square in the center of the plot. Values were transformed prior to analysis by taking the square root to normalize the data and stabilize the variance. Means within columns followed by the same letter are not significantly different according to Tukey’s pairwise comparisons (family error rate P = 0.05). The values are standardized to infection centers per 1 ft². y DAT = Days after treatment z Turbo TwinJet not available in 08 orifice size. Turbo Duo with two TT11004 orifices was substituted to obtain 08 (0.8 gal/min) flow rate. The results in 2007 were similar to findings by Kaminski et al. (7), in which air induction and XR TeeJet nozzles provided better control than TurfJet nozzles at a volume of 1 gal/1000 ft². The lack of differences among water rates is similar to findings by McDonald et al. (10) in which applications of propiconazole and/or chlorothalonil at water rates of 1.1 and 2.5 gal/1000 ft² were not significantly different. However, the results differ from another study by McDonald et al. (11) in which chlorothalonil performed better when applied at 1.1 compared to 2.5 gal/1000 ft². Those studies (10,11) were both conducted in fairway height turf. While Vincelli and Dixon (12) did not directly test water carrier volume, they observed that dollar spot control with both chlorothalonil and myclobutanil was positively associated with spray coverage at 1.5 gal/1000 ft², with the XR11004-VS and AI11004VS providing better disease control and more coverage on water sensitive paper than the 1/4TTJ04 and Raindrop RA-4 (35654-2). In contrast, in our study, the 0.5 gal/1000 ft² water rate had less coverage than the 1.0 and 2.0 gal/1000 ft² treatments but disease control was generally not reduced. The rate of chlorothalonil (3.2 vs 1.8 oz/1000 ft²), the pressure (35 vs 40 PSI), the cultivar (‘Penncross’ vs ‘A4’), and the mowing heights were different between the two sets of experiments, and those may have been factors. 2008 dollar spot development. In 2008, dollar spot levels were low through May and June. On 17 June, 7 days after the previous treatment, all nozzle-volume combinations reduced disease significantly compared to the untreated control except the XR flat-fan and TurfJet at 0.5 gal/1000 ft² and the Air Induction nozzle at 1.0 gal/1000 ft² (Table 3). On 9 July, 14 days after the previous treatment, no treatments reduced dollar spot compared to the untreated control, which had an average of 7.4 DSIC/ft². Dollar spot severity had increased significantly in the last few days of that 14-day spray interval, and the 1.8 oz/1000 ft² rate of chlorothalonil may have been too low. The manufacturer recommends application rates of 1.0 to 1.8 oz/1000ft² for intervals of 7 to 10 days, 1.8 to 3.25 oz/1000 ft² for intervals of 7 to 21 days, and 3.7 to 5.0 oz/1000 ft² when disease is already established. When disease pressure is high, proper fungicide rates and timing are critical even when a high-coverage nozzle is utilized (Table 3). Table 3. Dollar spot severity as influenced by nozzle type and spray volume, 2008.
w The Turbo TwinJet is not available in the 08 orifice size. A Turbo Duo with two TT11004 orifices was substituted to obtain 08 (0.8 gal/min) flow rate. x DAT = Days after treatment. y Values represent the mean number of dollar spot infection centers per plot for four replicates. The number of dollar spot infection centers were counted in a 38 × 19-inch rectangle in the center of the plot. Values were transformed prior to analysis by taking the square root to normalize the data and stabilize the variance. Means within columns followed by the same letter are not significantly different according to Tukey’s pairwise comparisons (family error rate P = 0.05). The values are standardized to infection centers per 1 ft². z The last two digits indicate the flow rate per nozzle, in GPM = gallons per minute, i.e., 02 = 0.2 GPM. Conclusions Nozzle selection and spray volume can influence the efficacy of chlorothalonil for dollar spot control. When applying chlorothalonil on putting green height turfgrass, nozzles such as XR, Air Induction, Turbo TwinJet, and Turbo Drop Twin Fan can be utilized with spray volumes as low as 0.5 gal/1000 ft² without sacrificing dollar spot control efficacy under disease pressure in Kansas conditions and possibly provide for greater area covered with a given tank size. In addition, certain drift-control nozzles can provide excellent disease control even though coverage is reduced somewhat compared to XR flat-fan nozzles. In this study, two nozzles with air induction technology (Air Induction and Turbo Drop Twin Fan) and a nozzle with a pre-orifice design (Turbo Twin Jet) provided dollar spot control comparable to the XR flat-fan across a range of water volumes. With increasing pressure to reduce drift and off-target effects, such nozzles may be an attractive option for golf course managers. Nozzles, such as TurfJet, with significantly lower coverage are less effective. However, no nozzle, even with 100% coverage, can overcome use of an overly low fungicide rate under high disease pressure. Acknowledgments We would like to thank Brandon Gonzalez and Andrew Lance (Kansas State University undergraduate research assistants) for technical assistance, Matt Giese (Syngenta Professional Products, Greensboro, NC) for initial discussions of the experimental goals, and Jack Fry (Department of Horticulture, Forestry, and Recreation Resources, Kansas State University, Manhattan KS) for critical review of the manuscript. We would also like to thank two anonymous reviewers for valuable suggestions. Partial funding was provided by Syngenta Crop Protection (Greensboro, NC). Contribution no. 09-313-J from the Kansas Agricultural Experiment Station. Literature Cited 1. Couch, H. B. 1995. Diseases of Turfgrasses, 3rd Edn. Krieger Publ. Co., Malabar, FL. 6.Fidanza, M. A., Kaminski, J. E., Agnew, M. L., and Shepard, D. Evaluation of water droplet size and water-carrier volume on fungicide performance for anthracnose control on annual bluegrass. Int'l Turfg. Soc. Res. J. In press. 7. Kaminski, J. E., Fidanza, M. A., Agnew, M., and Gregos, J. 2006. Impact of nozzle type on dollar spot control. (Abstr.) Phytopathology 96:S8. 8. Kennelly, M. M., and Wolf, R. E. 2008. Effect of nozzle type and water volume on dollar spot control in creeping bentgrass. Phytopathology 98:S80. 9. Matthews, G. A. 2000, Pesticide Application Methods, 3rd Edn. Blackwell Science Ltd., Osney Mead, Oxford, UK. 10. McDonald, S. J., and Dernoeden, P. H. 2006. Preventive dollar spot control in creeping bentgrass as influenced by spray volume and a spring application of fungicides, 2005. Fung. Nemat. Tests 61:T017. 12. Ott, R. L. 1993. An introduction to statistical methods and data analysis, 4th Edn. Duxbury Press, Belmont CA. 13. Shepard, D., Agnew, M., Fidanza, M., Kaminski, J., and Dant, L. 2006. Selecting nozzles for fungicide spray applications: Using the right nozzle may save your grass. Golf Course Manage. June: 83-88. 14. Smiley, R. W., Dernoeden, P. H., and Clarke, B. B. 2005. Compendium of Turfgrass Diseases, 3rd Ed. American Phytopathological Society, St. Paul, MN. 15. Syngenta. 2002. Water-sensitive paper for monitoring spray distributions, CH-4002. Syngenta Crop Protection AG., Basle, Switzerland. 16. Vargas, J. M. 1994. Management of Turfgrass Diseases, 2nd Edn. Lewis Publ., Boca Raton, LA. 18. Vincelli, P., and Dixson, E. 2008. Improving spray coverage improves dollar spot control. Golf Course Manage. 76:114-116. 19. Whitney, R. W. 2003. DropletScan Operators Manual. WRK of Oklahoma, Stillwater, OK. 20. Wolf, R. E. 2000. Equipment to Reduce Spray Drift. Online. Publication MF-2445 of the Kansas Ag. Exp. Sta. Kansas State Univ., Manhattan KS. 21. Wolf, R. E., and Daggaputi, N. P. 2009. Nozzle type effect on soybean canopy penetration. Appl. Eng. Agric. 25:23-30. |
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