Fungicides were evaluated for preventative control of spring dead spot in bermudagrass. This trial was conducted at the Walnut Creek Softball Complex in Raleigh, NC on ‘Tifway’ bermudagrass maintained under athletic field conditions. Mowing was performed twice weekly at a height of 1 in. with clippings returned, and the site was irrigated to prevent drought stress. Fertilizer was applied as 18-5-9 on 9 Apr, 5 Jun, 1 Aug, and 29 Aug 2002 (1 lb N/1000 sq ft) and as 0-0-60 on 17 Sep and 15 Oct 2002 (3 lb K/1000 sq ft). Fields were hollow tine aerified in April 2002, and then monthly from June through September 2002. Weed control was applied as Simazine (1 qt/A) on 15 Nov 2002, and as Pendulum 2G (100 lbs/A) on 25 Feb 2003. The experimental area was scouted in Spring 2002 while symptoms of spring dead spot were evident, and the trial was established in an area of uniform disease pressure. Plots were 5 ft x 6 ft and were arranged in a randomized complete block with four replications. Fungicides were applied in water equivalent to 2.5 gal per 1000 sq ft with a CO2 powered sprayer at 40 psi using TeeJet 8004 flat fan nozzles. Granular treatments were applied by hand using a shaker jar. All treatments were watered in with 1/4" of irrigation immediately after application. All treatments were initiated on 5 Sep 2002, and were reapplied at the appropriate intervals as indicated in the table. Percent turf area exhibiting spring dead spot symptoms were assessed on 21 Apr, 7 May, and 27 May 2003. Data were subjected to analysis of variance and means separation by Waller-Duncan k-ratio t test (k=100).

None of the treatments in this trial provided significant suppression of spring dead spot incidence compared to the Untreated Control. Spring dead spot symptoms were not observed in plots treated with Patchwork (96 oz) on the 7 May and 27 May rating date or in plots treated with Cleary’s 3336 (6.0 fl oz) on the 27 May rating date.

¹Application code indicates the application date(s) for each treatment component: A=5 Sept 2002; B=3 Oct 2002; C=5 Nov 2002; D=7 May 2003; E=15 May 2003.
²Values are means of four replicates. Means within columns followed by the same letter are not significantly different according to Waller-Duncan k-ratio t-test (k=100).

Evaluation of fungicides for control of spring dead spot, 2003-2004.

Fungicides were evaluated for their ability to control spring dead spot when applied on a preventative basis. This trial was conducted at the Walnut Creek Softball Complex in Raleigh, NC on ‘Tifway’ bermudagrass maintained under athletic field conditions. Mowing was performed twice weekly at a height of 1 in. with clippings returned, and the site was irrigated to prevent drought stress. The experimental area was scouted in Spring 2003 while symptoms of spring dead spot were evident, and the trial was established in an area of uniform disease pressure. Plots were 5 ft x 10 ft and were arranged in a randomized complete block with four replications. Fungicides were applied in water equivalent to 5 gal per 1000 sq ft with a CO2 powered sprayer at 40 psi using TeeJet 8008 nozzles. Granular materials were weighed individually for each plot and applied by hand using a shaker jar. All treatments were initiated on 3 Oct 2003, and some treatments were reapplied on 4 Nov 2003 as indicated in the table. Percent turf area exhibiting spring dead spot symptoms was assessed on 13 May 2004 using digital image analysis with SigmaScan software. Data were subjected to analysis of variance and means separation by Waller-Duncan k-ratio t test (k=100).

Spring dead spot pressure was high in 2003-2004 in the experimental area, with an average disease incidence of 14.31% in untreated plots according to digital image analysis. Only plots treated with Patchwork or Rubigan exhibited significantly less spring dead spot incidence than untreated control plots. Lynx applications reduced spring dead spot incidence to 2.16%, but this difference was not statistically significant. Multiple applications of 3336 and Endorse in the fall may be needed to provide significant control of spring dead spot in bermudagrass turf.

¹Fungicides were applied on 3 Oct 2003 (application code A) and 4 Nov 2003 (application code B).
²Values are means of four replicates. Means within columns followed by the same letter are not significantly different according to Waller-Duncan k-ratio t-test (k=100).

Influence of rate and application date on control of spring dead spot with fenarimol, 2003-2004.

Varying rates of fenarimol applied on different timing regimes were evaluated for control of spring dead spot. This trial was conducted at Walnut Creek Softball Complex on Field 4 in Raleigh, NC on ‘Tifway’ bermudagrass maintained under athletic field conditions. Mowing was performed twice weekly at a height of 1.5 in. with clippings returned, and the site was irrigated to prevent drought stress. Plots were 5 ft x 10 ft and were arranged in a split-plot randomized complete block with 4 replications. Application rates served as the main plots, whereas application dates were the sub-plots. Fungicides were applied in water equivalent to 5 gal per 1000 sq ft with a CO2 powered sprayer at 40 psi using TeeJet 8008 nozzles. Treatments were initiated on 1 Aug 2004 and were applied as indicated in the table. Percent turf area exhibiting spring dead spot symptoms was assessed on 12 May 2004 using digital image analysis. Data were subjected to analysis of variance and means separation by Waller-Duncan k-ratio t test (k=100).

Spring dead spot was severe in 2004, due to a wet fall and cold winter in 2003-04. All fenarimol application rates provided significant control of spring dead spot when averaged across all timings (Table 1). When treatments were initiated on 1 Aug 03, only the 4 + 4 fl oz and 6 + 6 fl oz treatments provided significant spring dead spot control. All treatments provided significant control of spring dead spot when initiated on 15 Aug 03 or 15 Sep 03. No significant differences were detected among treatments for the 1 Sep 03 or 1 Oct 03 application dates. There were no significant differences detected among application timings when analyzed across all Rubigan rates (Table 2). No phytotoxicity or other negative impacts on turfgrass quality were observed at any time during this trial.

Table 1. Spring dead spot incidence ratings for application timings.

Disease incidence on 12 May 04 (%)

¹Treatments were initiated on the dates indicated in the table. For split-applications, follow-up treatments were applied 14 days after the initial application.
²Disease incidence values from 12 May 04 rating date are means of four replicates. Means within columns followed by the same letter are not significantly different according to Waller-Duncan k-ratio t-test (k=100).

Table 2. Spring dead spot incidence ratings for all Rubigan rates.

¹Treatments were initiated on the dates indicated in the table. For split-applications, follow-up treatments were applied 14 days after the initial application.
²Disease incidence values from 12 May 04 rating date are means of four replicates. Means within columns followed by the same letter are not significantly different according to Waller-Duncan k-ratio t-test (k=100).

Heritage is a registered trademark of Syngenta Corp.
Banner MAXX is a registered trademark of Syngenta Corp.
Cleary's 3336 is a registered trademark of Cleary Chemical Corp.
Rubigan is a registered trademark
Patchwork is a registered trademark