2010 Evaluation of Fungicides for the Control of Microdochium Patch on an Annual Bluegrass Putting Green

Introduction

The purpose of this trial was to evaluate the effectiveness of various fungicides in controlling Microdochium patch (Microdochium nivale) on an annual bluegrass putting green.

Materials and Methods

The trial was initiated on February 22nd on an annual bluegrass (Poa annua) putting green located at Oregon State University’s Lewis-Brown Horticulture Farm in Corvallis, Oregon. The green was constructed using the “California method” where 12 inches of straight USGA sand was placed on top of a soil sub grade.  Irrigation pipe and flat tile drainage was installed on the sub grade before the sand was installed. Poa annua sod (purchased from Boss Sod, Canada) was laid in early May of 2009. The mowing height was reduced to 0.150 inches by the middle of July and remained there throughout the summer, fall, and winter. Soluble nitrogen applications were made weekly during the summer at a rate of 0.10 lbs of Nitrogen per 1,000 sq. ft. During fall and winter, 0.5 lbs of nitrogen per 1,000 sq. ft. was applied monthly.

Fungicide applications were made on a 3 week interval and were applied 3 times except for treatment 11 (Instrata) which was applied only twice because of phytotoxicity to the turfgrass. Granular products were applied with a shaker can after adding screened cat litter to bulk up the amount and then watered in for 6 minutes with the irrigation system. Spray products were applied with a two-wheeled bicycle sprayer using a CO2 bottle and a pressure valve. The products were applied with TeeJet 80015 nozzles at 30 psi in 2 gallons of spray solution per 1,000 sq.ft.

Daily temperature ranges and relative humidity for the dates of applications are listed in the table below:

On February 22nd, it began raining a couple of hours after the treatments were applied; a total of 0.14 inches of rain fell. No rainfall occurred on March 17th or April 9th.

Visual disease severity and plot quality ratings were taken on February 26th, March 17th, March 31st, April 9th, and April 20th. Disease severity ratings were based on percent plot cover from 0 – 100 percent. Data from each rating date were subjected to analysis of variance using a randomized complete block design with 3 replications. Differences between means were determined by Fisher’s LSD at the 5% level.

The treatments applied are listed below:

Results

All plots had a small amount of disease at the start of the trial but the average percent disease cover for all treatments was 0.26 percent or less calculated based on the number of disease centers times the area of each disease center.

The first 3 weeks of the trial had low disease pressure with the untreated check plots averaging 0.9 percent disease cover on March 17th. However, by March 31st, disease pressure had increased and the untreated check plots averaged nearly 8 percent disease cover. From March 31st until April 20th, the percent disease cover tripled to over 25 percent for the untreated check plots (see graph). This pattern tracks with rainfall. After February 22nd, rainfall decreased steadily from .05 inches on February 23rd to 0.1 inches by February 28th. For the first 23 days of March, it only rained .09 inches never exceeding .02 inches in a single day. The next 7 days of March (24th through the 30th), it rained 3.9 inches. And for the first 20 days of April, it rained 2.87 inches.
Generally, with the exception of FFII, the granular products were not effective in controlling Microdochium patch in this trial. FFII provided excellent disease control but there was slight phytotoxicity and fertilizer spotting on March 31 – two weeks after the second application. Plot quality improved by April 9th but the phytotoxicity was worse on April 20th, 11 days after the third application.

Of the liquid products, Interface SC provided the best disease control and turf quality. The middle rate of Interface (5.0 oz per 1,000) provided the best turf quality but was not significantly different than the 4.0 or 6.0 oz rates. Although Instrata (7.0 oz per 1,000 sq. ft.) provided 100 percent disease control, it caused severe phytotoxicity to the turf after two applications which indicates the rate was too high. Syngenta recommends 5.5 oz per 1,000 sq. ft. every 28 days.  Tartan and Cleary’s 3336 did not provide acceptable disease control. Cleary’s 3336 mixed with Interface (2.0 + 2.0 oz per 1,000) provided good disease control but slightly worse turf quality than Interface applied at 5.0 oz per 1,000 sq.ft. See data tables below.

Table 1: Percent Disease Ratings (0 – 100%)

Table 2: Turf Quality Ratings (1 – 9; 9 = best)