2010 Creeping Bentgrass-Dollar Spot Study

Nick Christians

June 1, 2011

This is the first of the 2011 research reports. It includes the 2010 results from our trial on creeping bentgrasses maintained at both fairway and green height. Tables 3 and 4 are jpg photos and you will need to click on them to be able to read them.

Creeping Bentgrass Dollar Spot Study

Christopher J. Blume and Nick E. Christians

Objectives

The objectives of this study are to determine the susceptibility of creeping bentgrass (Agrostis stolonifera) cultivars to dollar spot (Sclerotinia homeocarpa) under both green height and fairway height.

Materials and Methods

This fairway height (0.5”) and green height (0.25”) studies are being conducted at the Iowa State University Turfgrass Research Station it is part of a regional project being conducted at several of the Midwestern Universities. Both studies included 24 cultivars, although some of the cultivars differed on the two sites (Table 1). The green-height study area was established on a sand-capped area, and the fairway-height area was established on a native soil area (Nicollet clay-loam).

Both studies were established 17 September, 2008. The plots were allowed to mature until the spring of 2009. The plots were then split into untreated and fungicide treated halves. The study was conducted as a randomized split block design, with three replications.

Fungicide treatment timing was based on the cultivar ‘Declaration’, which is the most dollar spot tolerant cultivar in the study. Treatments were made to the green height plots when ‘Declaration’ was observed to have at least 5% of the plot area infested with dollar spot. The fairway height study area was treated when ‘Declaration’ was observed to have at least 10% of the plot area infested.

The fungicide mixture consisted of Emerald (0.18 oz product/1000ft²) and Daconil Ultrex (3.2 oz product/1000ft²), applied in 2 gallons water/1000ft². The applications were applied using a modified spray boom, with two TeeJet XR flat fan nozzles. In 2010, three applications were made 24 June, 19 August, and 4 October.

Results

‘Memorial’ and ‘Penncross’, and ‘LS-44’ had the best quality ratings in the green height study in 2010, whereas ‘Allister’ received the lowest rating. In the fairway height study, ‘Alpha’, ‘LS-44’, and ‘Memorial’ were the highest rated cultivars, and ‘Independence’, ‘Declaration’ and ‘SR 1150’ received the lowest quality ratings (Table 2).

‘Century’ and ‘Imperial’ showed the most damage from dollar spot in both September and October in the green height study (Table 3). ‘Memorial’, ‘Declaration’, and ‘Crystal Bluelinks’ had the least damage in untreated plots at the end of the season.

There was not as much dollar spot in 2010 as there was in 2009 on the fairway height bentgrass. At the first two ratings of the season, there was more dollar spot in the treated side than in the untreated side of the plot. These plots had not been treated since the fall before. The reason for this observation is unknown. In August, no dollar spot was observed on treated or on untreated sides of the plot. In September, ‘Southshore’ and ‘Century’ had the most dollar spot on the untreated side of the plots, whereas ‘Memorial’, ‘Independence’, and ‘Declaration’ had the least dollar spot. In October, ‘Crenshaw’ and ‘Century’ had the most dollar spot and ‘Memorial’, ‘Alister’, ‘Pennlinks II’ and ‘Memorial’ had the least (Table 4).

Table 1. Varieties of creeping bentgrass in commercial bentgrass demonstration trial.
Entry No.	Fairway Height Varieties	Green Height Varieties
1	L-93	L-93
2	T-1	T-1
3	Alpha	Alpha
4	Putter	Putter
5	Southshore	Southshore
6	Kingpin	Kingpin
7	Crenshaw	Crenshaw
8	Imperial	Imperial
9	Century	Century
10	Penncross	Penncross
11	A-4	A-4
12	Crystal bluelinks	Crystal bluelinks
13	Alister	Penn A-1
14	Pennlinks II	Penn G-6
15	007	007
16	MacKenzie	MacKenzie
17	Tyee	Tyee
18	SR 1150	SR 1150
19	Memorial	Memorial
20	Independence	Independence
21	Declaration	Declaration
22	LS - 44	LS - 44
23	Bengal	Bengal
24	Penn G-6	Alister

Table 2. Quality ratings for green-height and fairway-height cultivars of the creeping bentgrass demonstration trial.
		Quality¶		Quality
Cultivars (green)	2010		Cultivars (fairway)	2010
L-93	5.9β		L-93	6.4β
T-1	5.4		T-1	6.2
Alpha	5.4		Alpha	6.6
Putter	5.8		Putter	6.2
Southshore	5.8		Southshore	6.0
Kingpin	5.7		Kingpin	6.3
Crenshaw	6.2		Crenshaw	5.9
Imperial	5.6		Imperial	6.3
Century	5.5		Century	5.9
Penncross	6.2		Penncross	6.0
A-4	5.6		A-4	6.0
Crystal bluelinks	6.1		Crystal bluelinks	6.4
Penn A-1	5.9		Alister	6.1
Penn G-6	6.1		Pennlinks II	6.1
007	5.1		007	6.2
MacKenzie	5.3		MacKenzie	6.2
Tyee	5.0		Tyee	6.0
SR 1150	4.7		SR 1150	5.8
Memorial	6.3		Memorial	6.5
Independence	5.1		Independence	5.6
Declaration	5.0		Declaration	5.7
LS-44	6.2		LS-44	6.5
Bengal	5.7		Bengal	6.4
Alister	4.2		Penn G-6	6.4
LSD(0.05)	0.9		LSD(0.05)	0.6
¶Quality data rated on a scale of 9-1, with 9 = excellent turf; 1 = poorest quality; 6 = minimally acceptable. †Ratings are the average of three replications, averaged over the months of June to October. ‡Ratings observed only on fungicide-treated side of plot area. βRatings are the average of three replications, averaged over the months of May to October.