1999 Iowa Turfgrass Research Report

Trials were conducted on perennial ryegrass, maintained at fairway height, at the Turfgrass Research Area of the ISU Horticulture Research Farm near Gilbert, IA. The entire plot was inoculated on June 23 and August 7 with rye grain infested with isolates of Pythium aphanidermatum. NOTE: The grain used for the June 23 inoculation was infested with two isolates of P. aphanidermatum, one of which was resistant to metalaxyl. The grain used for the August 7 inoculation was infested with four isolates of P. aphanidermatum, two of which were resistant to metalaxyl.

Immediately after the infested grain was applied, the inoculated area was covered by Seedguard geotextile fabric for several days (June 23-24 and August 7-10). Fungicide treatments were applied after the cover was removed. Fungicides were applied with a modified bicycle sprayer at 30 psi and a dilution rate of 5 gal/1,000 ft². Fungicide applications after the first inoculation were made on June 25, then repeated at specified intervals on July 6, 9, 16, and 23. A single fungicide application, on August 14, was made after the second inoculation.

Weather conditions were conducive to Pythium blight during several periods after the June inoculation, but disease pressure was slight during June and July. Pythium blight symptoms appeared two weeks after the second inoculation. Disease development on August 25 was moderate. Ten treatments had significantly (LSD, P=0.05) less disease than the untreated check. No phytotoxicity was observed in any of the plots.

Table 1. 1998 Pythium blight trial on perennial ryegrass (fairway height).

			Interval	Mean number of infection centers
Trt	Product	Rate/1,000 ft2	(days)	June 29	July 10	August 25
1	-------	--------	----	0.0	0.0	8.75
2	BAS 500 2.09 EC	0.7 fl oz	14	0.0	0.0	3.75
3	Subdue MAXX	1 fl oz	14	0.0	0.0	0.0
4	Subdue MAXX	0.5 fl oz	14	0.0	0.25	1.0
5	Banol 6 EC	1.6 oz	14	0.0	0.0	1.25
6	Aliette Signature	4.0 oz	14	0.0	0.0	0.0
7	Heritage 50 WG	0.2 oz	14	0.0	0.0	0.75
8	Subdue MAXX	0.5 oz	14	0.0	0.0	2.5
	+Banol	1.6 oz
9	Subdue MAXX	0.5 oz	14	0.0	0.25	0.0
	+ Aliette Signature	4.0 oz
10	Subdue MAXX	0.5 oz	14	0.0	0.0	0.0
	+ Aliette Signature	2.0 oz
11	Heritage 50 WG	0.4 oz	10	0.0	0.0	2.5
12	Heritage 50 WG	0.4 oz	14	0.0	0.0	4.5
13	Heritage 50 WG	0.7 oz	14	0.0	0.0	4.0
14	Banol 6 EC	2 fl oz	14	0.25	0.0	1.0
15	Banol 6 EC	1 fl oz	14	0.0	0.0	1.0
	+ Fore FF	6.4 fl oz
16	Banol 6 EC	1 fl oz	14	0.0	0.0	5.0
	+ Heritage 50 WG	0.2 oz
17	Subdue MAXX	0.5 oz	14	0.0	0.0	2.75
	+ Fore F	6.4 fl oz
18	Subdue MAXX	0.4 fl oz	14	0.25	0.0	7.25
	+ Heritage 50 WG	0.2 fl oz
19	Aliette Signature 80 WP	8 oz	14	0.0	0.25	0.0
20	S-8172	6 fl oz	14	0.0	0.0	1.0
21	S-8174	2 fl oz	14	0.75	0.25	0.5
	+ S-5223	4.5 oz (add 1st)
22	S-7248	20.5 oz	14	0.0	0.0	0.5
23	S-7248	41 oz	14	0.0	0.0	1.5
24	UCC-A1562 20 SC	1 fl oz	14	0.25	0.25	0.5
25	UCC-A1562 20 SC	4 fl oz	14	0.25	0.25	5.25
26	UCC-A1562 20 SC	8 fl oz	14	0.0	0.0	8.5
	Least Significant Differencea			0.38	0.34	7.14

^aP = 0.05. n = 4 replications

ISU Horticulture:Publications:1999 Turfgrass Report

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