Effects of spray nozzle and fungicide mode of action on control of Microdochium patch on an annual bluegrass putting green in western Oregon
B.W. McDonald, C.M. Mattox, A.R. Kowalewski, Ph.D., and D.K. Mosdell, Ph.D.
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Many factors influence the efficacy of turfgrass fungicides, including fungicide application rate and intervals between applications, host susceptibility, fungicide resistance, environment, nozzle type, spray volume, fungicide topical mode of action, leaf coverage, and depletion rate (1).
Microdochium patch (Microdochium nivale) is a disease that affects turfgrass foliage. Microdochium patch is of major concern in humid, cool regions where annual bluegrass (Poa annua L.) turf is often dominant. To date, there is little published research showing results for the influence of nozzle types, fungicide topical mode of action, and spray volumes regarding Microdochium patch control. Therefore, the main objective of this field study was to evaluate the effect on Microdochium patch control from the interaction of nozzle type-spray volume combinations with fungicide topical mode of action.
†Digital images of treated water-sensitive paper (Spraying Systems Co., Wheaton, Ill.) were collected using an enclosed light box and analyzed to determine percent spray coverage (0%-100%) (3).
‡According to specifications from manufacturers (4).
§Lowercase letters represent a significant difference at a 0.05 level of probability. Analysis of variance was used to compute the level of significance.
Table 1. Effects of nozzle type-spray volume combinations on percent spray coverage, Corvallis, Ore.
Effects of nozzle-spray volume combinations on spray coverage
A spray nozzle coverage analysis was conducted using a completely randomized design with four replications. For this experiment, water was applied with four different nozzle-spray volume combinations: XR11004 (1 gallon/1,000 square feet) and XR11008 (2 gallons/1,000 square feet) (TeeJet, Glendale, Ill.) flat fans, which produce medium (226-325 µm) and coarse (326-400 µm) droplets, respectively, and 1/4TTJ04 (1 gallon/1,000 square feet) and 1/4TTJ08 (2 gallons/1,000 square feet) (TeeJet, Glendale, Ill.), which produce extremely coarse (500-650 µm) droplets (TeeJet Technologies, 2008). The water was applied with a CO2-pressurized backpack sprayer with a three-nozzle handheld boom at 30 pounds/square inch, 20 inches off the ground. Applications took place inside to avoid the effects of wind, and treatments were repeated four times for each nozzle.
Digital images were collected immediately following the spray application to water-sensitive paper (Spraying Systems Co., Wheaton, Ill.), which is rigid, yellow paper that is stained blue by liquid, using a Sony DSC-H9 camera (Sony, Tokyo, Japan) mounted on an enclosed light box measuring 24 inches long by 20 inches wide by 21.5 inches tall, and then analyzed using SigmaScan Pro (v.5.0, SPSS, Chicago) to determine percent spray coverage (0%-100%) (3). The threshold settings were adjusted to a hue of 135 to 255 to select the pixels that represented areas of the sensitive paper affected by the spray treatments (blue area); the saturation was set to a range of 0 to 100. Data were analyzed using SAS 9.3 Proc Mixed (SAS Institute, Cary, N.C.). The means were separated using Fisher’s LSD (0.05).
Figure 1. Examples of nozzle type-spray volume combinations (XR11004 and 1/4TTJ04 at 1 gallon/1,000 square feet [407 liters/hectare] and XR11008 and 1/4TTJ08 at 2 gallons/1,000 square feet [814 liters/hectare]) on surface coverage recorded at 30 pounds/square inch, directly beneath the center nozzle of the three-nozzle boom (19-inch spacing) held 20 inches off the ground in Corvallis, Ore. The dark blue areas are water-soaked, and the white areas are uncovered.
There was a large difference in spray coverage from the different nozzle-spray volume combinations (Table 1 and Figure 1). XR11008 nozzles (2 gallons/1,000 square feet) had the greatest spray coverage (86%), followed by XR11004 nozzles (1 gallon/1,000 square feet), which provided a spray coverage of 67%. The 1/4TTJ08 (2 gallons/1,000 square feet) provided a coverage of 56%, while the 1/4TTJ04 (1 gallon/1,000 square feet) provided the lowest coverage at 26%.
Effects of nozzle-spray volume combinations and fungicides on Microdochium patch
A field study was conducted at Oregon State University’s Lewis-Brown Horticulture Farm in Corvallis, Ore., from Jan. 25 to April 24, 2013 and 2014, on an annual bluegrass putting green mowed weekly at 0.150 inch. The experiment used a 3-by-4 factorial, plus control, treatment structure and a randomized complete block design structure with four replications. Factors included fungicide topical mode of action, and nozzle-spray volume combinations. Three different fungicides were used: fluazinam (Secure; Syngenta, Greensboro, N.C.), propiconazole (Banner Maxx II; Syngenta, Greensboro, N.C.) and difenoconazole with three different types of topical mode of action (contact, acropetal and translaminar with limited acropetal, respectively). The following application rates were used for the duration of this experiment: Secure at 0.5 fluid ounce/1,000 square feet (0.016 pound a.i./1,000 square feet), Banner Maxx II at 1.0 fluid ounce/1,000 square feet (0.01 pound a.i./1,000 square feet) and a difenoconazole solution at 0.4 fluid ounce/1,000 square feet (0.009 pound a.i./1,000 square feet). While difenoconazole was a treatment in this experiment, it is only commercially available in a mix with azoxystrobin (Briskway; Syngenta, Greensboro, N.C.). Five applications of each product were made to their respective plots on 21-day intervals, with the first application occurring in the first week in January 2013 and 2014. Fungicides were applied with a CO2-pressurized backpack sprayer with a three-nozzle handheld boom at 30 pounds/square inch. Applications were performed with the same four nozzle-spray volume combinations as in the first study.
*Significant between means of nozzles within a fungicide (rows) at P = 0.05. Preplanned con-trasts were used to compute the level of significance.
**Significant between means of nozzles within a fungicide (rows) at P = 0.01. Preplanned con-trasts were used to compute the level of significance.
***Significant between means of nozzles within a fungicide (rows) at P = 0.001. Preplanned contrasts were used to compute the level of significance.
†Digital images collected using an enclosed light box and analyzed to determine percent dis-ease severity (0%-100%).
‡Five applications of each product (Secure at 0.5 fluid ounce/1,000 square feet [0.016 pound a.i./ 1,000 square feet], Banner Maxx II at 1.0 fluid ounce/1,000 square feet [0.01 pound a.i./1,000 square feet], and difenoconazole solution at 0.4 fluid ounce/1,000 square feet [0.009 pound a.i./1,000 square feet]) were made on 21-day intervals, with the first application in Jan-uary 2013 and 2014.
§Disease severity in control treatments was 24.8% in March 2013, 40.5% in April 2013, 0.8% in March 2014, and 11.7% April 2014.
Table 2. Percent disease severity for XR11004 vs. 1/4TTJ04 nozzles at the 1 gallon/1,000 square foot spray volume in Corvallis, Ore., in March and April of 2013 and 2014.
To determine percent disease severity, digital images (four subsamples/plot) were collected in March and April of 2013 and 2014 using the camera and light box setup described above, and analyzed using Sigma-Scan Pro (3). The difference between percent green cover and 100% was used to quantify percent disease severity (2). Data were analyzed using PROC Mixed (SAS; ver. 9.3, SAS Institute Inc., Cary, N.C.). There were significant differences between year and month, and interactions between these factors and the remaining factors (fungicide and nozzle) were significant; therefore, the data were analyzed and presented by year and month separately. Additionally, preplanned contrasts were used to answer specific questions related to the effects of nozzle types on each fungicide.
For applications at 1 gallon/1,000 square feet spray volume, the plots treated with XR11004 nozzles had lower percent disease severity than the 1/4TTJ04 nozzles averaged across all fungicides on three of the four rating dates (March and April 2013, and April 2014) (Table 2).
Percent disease severity was reduced with difenoconazole or Banner applied with the XR11004 nozzles compared to the 1/4TTJ04 nozzles on one of the four rating dates. No differences in percent disease severity were detected between XR11004 and 1/4TTJ04 nozzle treatments with Secure.
At the 2 gallons/1,000 square feet spray volume, plots treated with XR11008 nozzles had lower percent disease severity compared to the 1/4TTJ08 nozzles regardless of fungicide treatment in March and April 2013 (Table 3). No differences were found between nozzle treatments when percent disease severity was averaged over all fungicides in March and April of 2014. Percent disease severity was decreased with Secure, Banner or difenoconazole when applied with XR11008 nozzles compared with 1/4TTJ08 nozzles on April 2013. Difenoconazole reduced percent disease severity in March 2013 with XR11008 vs. 1/4TTJ08 nozzles.
These findings suggest nozzles that produce smaller droplets and higher coverage are important to maximize control of Microdochium patch, regardless of whether the spray volume is 1 or 2 gallons/1,000 square feet. Nozzle type and droplet size did not consistently result in improved disease control; however, the nozzle type did provide improved control in some cases, giving turf managers reason enough to use XR11004 or XR11008 rather than 1/4TTJ04 or 1/4TTJ08, considering the change will not generate a cost difference.
Acknowledgments
This paper is republished from Crop, Forage & Turfgrass Management, Volume 2. doi: 10.2134/cfthm2016.03.0018. © 2016 American Society of Agronomy and Crop Science Society of America, 5585 Guilford, Road, Madison, WI 53711. This is an open-access article distributed under the CC BY-NC-ND license (www.creativecommons.org/
licenses/by-nc-nd/4.0).
*Significant between means of nozzles within a fungicide (rows) at P = 0.05. Preplanned contrasts were used to compute the level of significance.
**Significant between means of nozzles within a fungicide (rows) at P = 0.01. Preplanned contrasts were used to compute the level of significance.
***Significant between means of nozzles within a fungicide (rows) at P = 0.001. Preplanned contrasts were used to compute the level of significance.
†Digital images collected using an enclosed light box and analyzed to determine percent disease severity (0%-100%).
‡Five applications of each product (Secure at 0.5 fluid ounce/1,000 square feet [0.016 pound a.i./ 1,000 square feet], Banner Maxx II at 1.0 fluid ounce/1,000 square feet [0.01 pound a.i./1,000 square feet], and difenoconazole solution at 0.4 fluid ounce/1,000 square feet [0.009 pound a.i./1,000 square feet]) were made on 21-day intervals, with the first application in January 2013 and 2014.
§Disease severity in control treatments was 24.8% in March 2013, 40.5% in April 2013, 0.8% in March 2014, and 11.7% April 2014.
Table 3. Percent disease severity (0%-100%) for XR11008 vs. 1/4TTJ08 nozzles at the 2 gallon/1,000 square foot spray volume in Corvallis, Ore., in March and April of 2013 and 2014.
Literature cited
- Latin, R. A 2011. Practical guide to turfgrass fungicides. The American Phytopathological Society. St. Paul, Minn., p. 79.
- Obasa, K., J. Fry and M. Kennelly. 2012. Susceptibility of zoysiagrass germplasm to large patch caused by Rhizoctonia solani. HortScience 47:1252-1256.
- Richardson, M.D., D.E. Karcher and L.C. Purcell. 2001. Quantifying turfgrass cover using digital image analysis. Crop Science 41:1884-1888. doi: 10.2135/cropsci2001.1884
- TeeJet Technologies. 2008. Catalogue 50A. TeeJet Technologies, Wheaton, Ill., p. 179.
B.W. McDonald is a senior faculty research assistant, C.M. Mattox is a graduate student, and A.R. Kowalewski is an assistant professor in the Department of Horticulture at Oregon State University, Corvallis, Ore. D.K. Mosdell is technical manager in the western U.S. for Syngenta, Greensboro, N.C.