1999 Iowa Turfgrass Research Report

Trials were conducted at the Iowa State University Horticulture Research Farm near Gilbert, Iowa. Fungicides were applied to ‘Penncross’ creeping bentgrass maintained at 5/32-inch cutting height, using a modified bicycle sprayer at 30 psi and a dilution rate of 5 gal/1,000 ft². The experimental design was a randomized complete block with four replications. All plots measured 4 ft x 5 ft. Five days after inoculation of the entire plot with rye grain infested with the dollar spot pathogen, fungicide applications began on June12. Subsequent applications were made on June 19, June 26 and on July 3, 10, 17, and 24.

Dollar spot symptoms were first observed on June 26. Disease development on untreated check plots was light on 29 Jun and moderately severe on July 10 and 16. Most, but not all, fungicide treatments exhibited significantly (LSD, P=0.05) less disease than the untreated check. Phytotoxicity (browning of tips of grass blades) on plots treated with AMV 300 became progressively worse during July, and was more severe at the 2 oz than the 1 oz rate.

Table 1. 1998 Dollar Spot Trial at ISU Horticulture Station.

			Interval	Mean % Plot Diseased
Trt	Product	Rate/1,000 ft2	(days)	June 29	July 10	August 25
1	-------	-------	--	4.0	17.5	22.5
2	Chipco 26 GT	2 oz	14	0.0	0.0	0.0
	+ Cleary's 3336 F	2 fl oz
3	Cleary 3336 50 WP	2 oz	14	0.0	0.0	0.0
4	Spectro 90 WDG	4 oz	14	0.0	0.0	0.0
5	Spectro 90 WDG	8 oz	14	1.5	0.0	0.0
6	WAC 75	5 oz	14	0.0	0.0	0.0
7	WAC 76	5.3 oz	14	0.0	0.0	0.0
8	Thalonil 90 DF	3.5 oz	14	2.2	2.8	4.0
9	TRA-0232	3.5 oz	14	2.1	4.8	5.8
10	BAS 505 50 DF	0.11 oz	14	0.2	0.3	0.0
11	BAS 505 50 DF	0.14 oz	14	0.3	0.1	0.3
12	BAS 505 50 DF	0.18 oz	14	0.1	0.0	0.0
13	BAS 505 50 DF	0.18 oz	28	0.0	1.5	1.9
14	BAS 505 50 DF	0.26 oz	28	0.1	1.1	1.2
15	BAS 510 4.17 SC	0.11 fl oz	14	2.8	13.0	14.5
16	BAS 510 4.17 SC	0.14 fl oz	14	2.4	0.4	0.2
17	BAS 510 4.17 SC	0.18 fl oz	14	4.1	3.3	1.8
18	BAS 510 4.17 SC	0.18 fl oz	28	3.6	18.0	20.8
19	BAS 510 4.17 SC	0.26 fl oz	28	1.5	8.0	9.0
20	Banner MAXX 1.24 MC	1.0 fl oz	21	0.0	0.0	0.0
	+ Thalonil 90 DF	6 oz
21	Heritage 50 WP	0.2 oz	14	2.3	3.3	3.7
	+ Daconil Ultrex	3.8 oz
22	Daconil Ultrex	3.8 oz	14	2.0	3.3	8.3
23	Eagle 50 WP	0.5 oz	14	1.1	0.0	0.0
	4th and later sprays:
	Daconil Ultrex	3.8 oz	14
24	Eagle 50 WP	1.2 oz	28	0.5	3.1	2.0
25	ZeroTol	0.5 fl oz/80 ft2	7	4.0	18.3	21.3
26	Bayleton 50 DF	0.25 oz	14	2.4	0.3	0.3
	+ Daconil Ultrex	1.82 oz
27	Lynx 45 WP	0.28 oz	14	0.9	0.1	0.0
	+ Daconil Ultrex	1.82 oz
28	Bayleton 50 DF	0.25 oz	14	1.3	0.7	0.3
29	Lynx 45 WP	0.28 oz	14	0.3	0.1	0.0
30	AMV 300	1 oz	14	3.8	12.5	18.8
31	AMV 300	2 oz	14	3.5	17.5	20.5
32	UCC-A1562 20 SC	1 fl oz	21	1.0	0.3	2.3
33	UCC-A1562 20 SC	4 fl oz	21	0.1	0.3	0.0
34	UCC-A1562 20 SC	8 fl oz	21	0.0	0.0	0.0
35	Heritage 50 WG	0.4 oz	21	1.4	0.0	4.1
	Least Significant Differencea			1.8	8.9	8.4

^aP = 0.05. n = 4 replications.

ISU Horticulture:Publications:1999 Turfgrass Report

College of Agriculture