Monthly Archives: May 2013

Examining Resistance to DMI Fungicides: Research at the University of Guelph

Dollar spot disease on Kentucky bluegrass showing the tip yellowing and a dark band at the base of the lesion. Photo courtesy Tom Hsiang

By Tom Hsiang, PhD

Propiconazole, a DMI fungicide, became registered for use on turfgrass in 1994. Due to the recent discovery of DMI-resistant isolates of the dollar spot pathogen in the Great Lakes States, there was concern resistance would develop in Ontario. This author started a study in 1994 to look at baseline sensitivity of the dollar spot pathogen to DMI fungicides. A graduate student, Wayne Barton, worked on sensitivity to propiconazole, while other students and lab members worked on sensitivity to other DMI fungicides.

From eight locations throughout southern Ontario, the team found most populations of the dollar spot pathogen were sensitive to DMI fungicides. However, there was one population near the U.S. border with reduced sensitivity to DMI fungicides, and the team suspected there had been previous exposure to DMI fungicides in this population.

Read the full article: Examining Resistance to DMI Fungicides

Examining Resistance to DMI Fungicides: Anti-resistance strategies

Dollar spot disease on Kentucky bluegrass (left) and creeping bentgrass (right). Photo courtesy Tom Hsiang

By Tom Hsiang, PhD

A case study on the development of DMI fungicide resistance illustrates some of the conditions that may lead to disease control failure. At a golf course outside of Chicago, where resistant isolates were found, an older variety of creeping bentgrass was used that was very susceptible to dollar spot. This likely led to greater frequency of fungicide use. Secondly, nitrogen levels were purposely kept low to prevent the occurrence of other diseases, such as Pythium blight, which again may have contributed to greater fungicide use because dollar spot disease is favoured by low-nitrogen regimes. Thirdly, DMI fungicides were used extensively for several years.

General recommendations to prevent DMI resistance problems in fungi include:
● not using repeated applications of DMI alone;
● using mixtures or alternating with non-DMI fungicides;
● reserving DMI use for the critical part of the season;
● using label rates rather than reduced doses; and
● using other measures such as resistant varieties and cultural practices.

Read the full article: Examining Resistance to DMI Fungicides

Digging in the Dirt: Undue emphasis

This river of green in an otherwise phosphorus-deficient stand of creeping bentgrass was caused by a few drips of a phosphorus solution coming off a leaky spray boom. The subsequent irrigation washed the drips across the plot and the grass greened up, showing not much phosphorus is needed for the grass to respond. While creeping bentgrass tends to turn purple when phosphorus is low, annual bluegrass tends to turn yellow. Photo courtesy Doug Soldat

By Doug Soldat, PhD

Without understanding all the limitations covered in this article, it is easy to see how one could get carried away by attempting to find the ‘ideal’ level of every nutrient in the soil. One common over-interpretation is when soil test reports recommend balancing the soil cations using the base cation saturation ratio (BCSR). These use the same methods as previously described, but recommend the soil cations (i.e. calcium, magnesium, and potassium) are balanced in an ‘ideal’ ratio. Unfortunately, after years of research, there is still no evidence this approach works—the only thing known for certain is someone following this approach ends up spending a lot more money.

To avoid over-interpretation or relying solely on the laboratory’s (or consultant’s) interpretations of the soil-testing results, this author recommends results be compared with Pace Turf’s Minimum Level for Sustainable Nutrition (MLSN) Guidelines. Instead of drawing interpretations from a single study, these minimum levels are based on thousands of soil-testing results where the turf was deemed to be performing average or above average (all soil samples from poor performing turf were thrown out). The ‘minimum level’ was set at the lower one-third of the data set, meaning about 33 per cent of the soil samples with good turf had levels (e.g. for potassium or phosphorus) below that minimum.

Read the full article: Digging in the Dirt: The reliability of soil testing

Reconstructing the Derrick Club: Back to the Derrick

A major component of the redesign plan at the Derrick Club involves rerouting a section of the course currently comprising holes five through eight (yellow). This eliminates potential danger at the current fifth and ninth holes and also enhancing variety by creating two long par-fours at the proposed 14th and 15th holes, and a short par-three at hole 16. Photo courtesy Jeff Mingay

By Jeff Mingay

Scheduled to be implemented over two years, the Derrick renovation project is driven by the necessity of resolving some very fundamental problems. Most important is the installation of a comprehensive sub-surface drainage system, designed in conjunction with Geoff Corlett, president of TDI Golf (the general contractor on the project). This drainage system comprises 152-mm (6-in.) spur lines servicing each hole that connect to two 305-mm (12-in.) mainlines installed deep enough in the ground they will never be compromised.

Ten new holes and the aforementioned short game practice area will be built during phase one of this project, in spring/summer 2013, while club members continue to play the nine existing holes. Those new holes will be open for play while the remainder of the new course is completed the following summer. All 18 holes of the new course will debut in spring 2015.

Read the full article: Reconstructing the Derrick Club: Phase One

Restoring Fairmont Hot Springs Resort: Cleaning up the holes

Hole 16, a par-three and 138 m (151 y), had the largest amount of debris in both quantity and size. Some of the rocks were the size of golf carts. Photo courtesy Fairmont Hot Springs Resort

By Peter Smith, MBA, CPGA

From July 15 to August 31, the weather was co-operative with mostly dry, sunny, hot days. Mountainside Golf Course was built in the late 1960s and is, as Carrick describes it, a ‘parkland-style’ golf course. The irrigation system is the original manual system with two sources of water—the primary one is Fairmont Creek and the secondary is Cold Stream Creek.

As the debris slide came down Fairmont Creek, one of the casualties was the primary irrigation source for Mountainside. The intake system and 0.75 km (0.5 mi) of supply line were gone. Additionally, an immeasurable amount of silt, small gravel, and small sticks were driven into the system. As if the project to reconstruct the seven holes was not enough, the challenge of maintaining the rest of the course increased as the weather grew hotter. Redirecting the secondary source and constantly cleaning out the plugged lines was a major task. Pumps in creeks and waterways were also used where possible. At times, fire hydrants were tapped to supplement the source.

Read the full article: Restoring Fairmont Hot Springs Resort