Control of Fairy Ring with Ultra Fairy Ring Solution (2002)

Darrell K. Tompkins, Mark A. Anderson and James B. Ross

Summary

Fairy ring is one of the major diseases of turfgrasses in the Prairie region of North America.  Large rings can form on turf and cause physical damage to turf with large scars.  The cause of death of the turf is thought to be as a result of moisture stress, parasitism by the fungus, or as the result of a toxin produced that damages root hairs.  Considerable work has been conducted over the years, but no control strategies have proven effective.

The objective of this trial was to determine the effect of an experimental soap solution, called Ultra Fairy Ring Solution, for the control of fairy ring.  Two experiments within this trial were conducted to evaluate the product.  The first experiment examined the effectiveness of the product on control of the fungus in culture plates and the second experiment looked at controlling the fairy ring fungus in the greenhouse.

In the laboratory study various rates of the product were incorporated into a sterile culture media.  A 5mm plug of the fairy ring fungus, Marasmius oreades, was placed on the media and growth characteristics were measured.  The Ultra Fairy Ring Solution was compared with two fungicides, Heritage and ProStar, that have reportedly had some control of the fungus.  The higher rates of the Ultra Fairy Ring Solution effectively suppressed growth of the fungus in the culture plates.  As well, the fungicide Heritage effectively suppressed growth while the fungicide ProStar, which is licensed for use on fairy ring in the United States, was not as effective as the other two products.

The greenhouse experiment was established in an attempt to duplicate field conditions in a more controlled environment.  This experiment would provide information on rates of application that may be effective in a subsequent field study.  In order to show that the product is effective evidence of eradication of the fairy ring fungus is necessary.  Some of these characteristics would be:

·         no reduction in turfgrass growth

·         moisture content would increase and be similar to adjoining soils

·         mycelium of the fungus is completely absent in the soil

·         scarred area on turf is completely healed

·         no evidence of ring symptoms i.e. stimulated green area

·         no evidence of mushrooms in the area around the ring.

In the greenhouse study, above ground plant parts were clipped and the plant material was weighed in order to determine whether there was a growth response to the addition of the product.  An increase in growth was recorded in almost all the treatments.  It was important to note that there was a slight decrease in growth for the highest treatment rate, which would indicate that this rate was too high.  However, there was no evidence of a phytotoxic reaction to this or any of the other treatments.

The Ultra Fairy Ring Solution Product increased the moisture content in the soil for many of the treatments.  Generally, when moisture content increased an increase in area cover of the turf was also noted.  A subjective analysis as well as digital imaging analysis was used to determine area cover ratings.  The digital imaging analysis proved to be a more precise way of detecting differences between treatments.

Although, there was a reduction of the fungus in the soil, the effect did not appear to as a result of the product application.  Increased watering practices may have reduced the amount of fungus.  Although at times there were mushrooms present, mushroom counts differences between treatments were not significantly different.

In the laboratory study, application of the Ultra Fairy Ring Solution suppressed the growth of the fungus.  In the greenhouse experiment, application of the Ultra Fairy Ring Solution increased growth and area cover of the turf, and increased moisture content in the soil.  Although fungal growth in the soil decreased, it could not be determined whether this effect was as a result of the application of the product or as a result of increased watering in the greenhouse.

Introduction

Fairy ring is one of the major diseases of turfgrasses in the Prairie region of North America.  Large rings can form on turf and cause physical damage to turf with large scars.  These scars are a particular annoyance to homeowners who employ a number of control strategies to rid their lawns of fairy ring.  Considerable work has been conducted over the years, but no control strategies have proven effective.

Many researchers have speculated as to the cause of death of the turf.  Filer (1964) indicated that death of turf within the ring may be as a result of moisture stress, parasitism by the fungus, or as the result of a toxin produced that damaged root hairs.  He reasoned that the drought condition created by the fungus was not the only factor that would contribute to the death of the turf.  He went on to say that the mycelial mat created by the fungus could not restrict the turf from obtaining adequate moisture from the soil.  He, therefore, felt that the presence of hydrogen cyanide may be an important factor.  Ramsbottom (1953) on the other hand contended that the death of the turf was due to a lack of moisture.

Control strategies may therefore decrease the mycelial mat, increase moisture content of the soil, and/or reduce the hydrogen cyanide content of the soil.  It is important to examine the changes in these factors when determining the effectiveness of new fungicides as control agents.  However, this has been difficult to accomplish as there is often great variability in ring severity, soil moisture conditions, and mycelial mat within the soil.  Measuring minute differences in treatments may assist in the development of a progressive control strategy.  Richardson et al, 2001 used digital imaging analysis to accurately measure area cover in turf.  This methodology may be able to measure small differences for various parameters in fairy ring studies.

The objective of this trial was to determine the effect of an experimental soap solution, called Ultra Fairy Ring Solution, for the control of fairy ring.  This experimental material has shown good penetration properties in other applications and may be effective in delivering the solution to the fungus that resides in the soil.

Methodology and Materials

Greenhouse Study

Dormant turf samples were collected from fairy rings with pronounced scaring in late October 2001.  Samples were selected to capture the interface between the outside edge of the scar and the surrounding turf.  Large prismatic turf blocks were removed from the rings.  Later, using a 20cm diameter circular cutter, the field samples were trimmed to a depth of 10cm.  These cores were placed into 20cm plastic pots and the soil crumb liberated from trimming the core was firmly packed around the edge of the core.  The pots were well watered, placed into a greenhouse and were allowed to grow-on for six weeks prior to the commencement of the trial.

The trial was setup in a completely randomized block design (CRBD).  Nine different rates of the product and one untreated control were tested.  The cores used in the trial were selected for each replication based on two criteria: firstly, the percent of actively growing turf cover on the core; and lastly, the percent soil moisture content of the core.  The area cover of each of the turf cores was assessed using the National Turfgrass Evaluation Program (NTEP) scale.  This scale subjectively ranked area coverage on a 1 to 9 basis, where 1 = no live turf cover, and 9 = complete area coverage.  Cores with a lower percentage of area cover (a rating of 2 or 3) were placed in the first and second replications.  Cores with a higher percentage of area cover (a rating of 4 to 8) were organized in an ascending order and placed in the third and fourth replications.  All turf samples with a soil moisture content greater than 25 percent were not selected for the trial.  The treatments were randomly assigned to a pot in each of four replications.

The greenhouse provided a consistent growing environment, where temperatures were maintained at 20^o C during the day and 10^o C nights, with a minimal deviation of +/- 2^oC.  The turf pots continued to receive 16 hours of supplemental lighting from both sodium halide and mercury vapor light sources.  Initially, the pots received topical applications of water twice a week.  However, in the third week of the trial, a physiological drought stress was present throughout the trial; which necessitated an additional water application per week.  The turf did not receive supplemental fertilization during the trial.  The turf was regularly clipped at a height of 5 cm to stimulate the tiller production of the turf.

Prior to the application of the treatments each pot was aerated with a solid tine aerator (5 holes per core at a depth of 8 cm).  The treatment rates were calculated on an area basis, with a 20cm diameter core having an area of 0.0314 m².  The product rates were estimated based on a field rate from earlier experimentation.

The treatments consisted of:        

1)     No product applied                         6)    1X rate =    6.666 litres /m²

2)     1/16X rate  0.416 litres /m²            7)    2X rate =    13.32 litres /m²

3)     1/8X rate = 0.833 litres /m²            8)    4X rate =    26.64 litres /m²

4)     1/4X rate = 1.665 litres /m²            9)    6X rate =    39.96 litres /m²

5)     1/2X rate = 3.333 litres /m²          10)    8X rate =    53.28 litres /m²

A confinement ring was firmly placed around the circumference of the core prior to the application of the treatment.  The ring improved the penetration of product into the core and reduced the risk of the treatment running down the sides of the pot.  The treatments were applied as a single application.  The product was slowly poured over the entire core. Treatments 9 and 10 required a significant amount of time to apply and the turf cores became highly saturated with the product.  After the liquid was completely absorbed into the core, the confinement ring was removed.  All the pots were watered with potable water at the completion of the treatment phase.

In order to show that the treatments are effective evidence of eradication of the fairy ring fungus is necessary.  This would be:

·         mycelium is completely absent in the soil

·         moisture content would have increased and be similar to adjoining soils

·         scarred area on turf is completely healed

·         no reduction in turfgrass clipping yields

·         no evidence of ring symptoms i.e. stimulated green area

·         no evidence of mushrooms in the area around the ring.

The treatments were assessed on a number of occasions throughout the trial period.  Prior to the application of the treatments an initial baseline value for: 1) the percent turf cover and 2) the percent soil moisture content was determined for each pot.  While the trial was on going, the treatments were evaluated for: 3) the phytotoxicity of the treatment to the turf; 4) the occurrence of fruiting bodies, and; 5) the changes in area covered by the turf.  At the conclusion of the trial the treatments were evaluated for: 6) the dry matter yield, 7) the presence of mycelium in the core, 8) the final percent area cover and 9) the final soil moisture content.

In addition to rating the area cover of the treatments with the NTEP scale, a second method was implemented.  Based on the premise that using a more objective method of measuring area coverage would increase the precision and a better separation of the treatments would result.  The second method of determining area coverage utilized a Canon digital camera (model PC1012) and the Sigma Scan Pro5 computer program, (spacial analysis software).  With this method the percent of area cover of each treatment was quantified.  The process involved two steps: 1) determine the number of green pixels (represents live turf) that were present in the digital image, (hue range of 47 to 126 and a saturation of 15% to 100%), and 2) convert the number of pixels to a percent area by dividing the number of green pixels by the total number of pixels in the image (Richardson et al, 2001).

The soil moisture content of each treatment was established using a Campbell Scientific HydroSense^TM moisture meter.  Each turf pot was probed in 3 different locations.  The readings were combined to generate a mean percent moisture value for each treatment.

The trial was rated on the third, the seventh and the fourteenth day after the application of the treatments for visual signs of physical stress or damage to the turf.  The rating scale was based on the pesticide injury protocols from the ECW Western Canada Weeds Section.

The presence of fruiting bodies (mushrooms) were assessed on Day 14 and just prior to the digital imaging of the treatments on Day 31 and on Day 56 of the trial.  To numerically describe this observation; a value of 1 was assigned to the treatments where no fruiting bodies were present and a value of 2 was assigned to the treatments where fruiting bodies were present.  All the bodies were removed after an assessment was completed.

Changes in area covered by the turf were captured using the digital image analysis method mentioned above.  The image of a treatment captured on Day 31 and Day 56 was compared with the baseline image of the treatment collected at the beginning of the trial.  The overall change in area covered corresponds with the effectiveness of the treatment.

The dry matter content was determined by measuring the dry weight of the verdure (all live vegetative material above the crown) clipped from each of pot.  Each sample was packaged and placed into a drying oven at a temperature of 75^o C for a period of 48 hours.  After the internal moisture was removed, the remaining organic matter was weighed.

The mycelium rating required the destructive separation of the sample.  A 1 – 5 rating scale, where 1 = no mycelium present, and 5 = excessive, was used to rate the level of infestation.  Both the bottom and the interior sections of each core were rated.  An overall value for the treatment was determined by combining the interior and bottom scores together

Laboratory Study

The effectiveness of Ultrasol fairy ring solution was compared with two industry products on a single isolate of Marasmius oreades obtained from the Alberta Environmental Research Station at Vegreville, Alberta.

Using methodology similar to that used by Blenis et. Al 1997, the trial was setup in a completely randomized block design (CRD) with two factors (Table 1).

Factor A compared three products: 1) Prostar, 2) Heritage and 3) Ultra Fairy Ring Solution, while factor B compared an untreated control with six different rates of each product.  The treatments were randomly arranged and replicated four times.

Table 1:  Product Treatment Rates – Laboratory Study

Preparation of the Treatments

One litre of sterile culture media was prepared for each of the products.  Thirty-nine grams of potato dextrose agar (PDA) was dissolved in 1 litre of distilled water for both the Heritage and the Prostar portion of the trial.  For the Ultra Fairy Ring Solution, which was already a prepared solution, the PDA was directly added to 1 litre of the product.  The culturing media was sterilized by autoclaving at 121^oC for fifteen minutes.  The flasks were later transferred to a water bath and allowed to cool to 45^o C before adding the products.  With the amount of product per culture plate being very small (Table 2), the following dilution series was entered into for each of the products.  A 200ml stock solution at the 8X rate was prepared.  The products were weighed out and dissolved in the sterile liquid agar.

A magnetic stirring table was used to thoroughly mix the stock solution.  A sub-sample of stock solution was incorporated into additional sterile PDA to create 100ml lots for each of the required treatments.  Under a flow hood, 15ml from each of the 100 ml lots was poured into separate culture plates.  The plates were allowed to cool to room temperature prior to entering the inoculation stage of the trial.

Table 2:  Product Required for 15ml of PDA Media (quantity of one culture plate)

Inoculation and Assessment

Working under a sterile environment, 5mm plugs of Marasmius oreades were extracted from activity growing cultures of the isolate.  The plugs were inverted and placed with the top surface contacting treated media.  Four plugs were transferred to each of the treated culture plates.  The plates were sealed with parafilm and moved to a dark incubation room with a constant temperature of 26^oC.  The culture plates were monitored on a daily basis.  On the third day after being inoculated, the size of the mycelium colonies on the control had significantly increased, marking the beginning of the measurement phase of the trial.  The diameter of each colony was measured and the size of the colony was determined by the average of two perpendicular measurements.  The cultured were measured once more, (7 DAT) before the colonies on the untreated control had completely filled the culture plate.

Results and Discussion

In the laboratory study the higher rates of the Ultra Fairy Ring Solution effectively suppressed mycelial growth in the culture plates.  As well, the fungicide Heritage effectively suppressed mycelial growth in the culture plates.  The fungicide ProStar, which is licensed for use on fairy ring in the United States, was not as effective as the other two products for suppression (Table 1).

Table 1  Mean Size (mm) of the M. oreades colonies 3 and 7 Days After Inoculation.

                  * Values that have the same letter as a suffix are not significant from each other

At no time was there any evidence of a phytotoxic reaction to any of the treatments of the Ultra Fairy Ring Solution (data not shown).  This would indicate that even at the high rates of application the product was not toxic to the turf.

Mycelium ratings were not significantly different between treatments.  It appeared that the presence of mycelium was less than when collected from the field.  The summer of 2001, leading up to the sampling period, was characterized by severe drought conditions which may have increased the presence of mycelium in the field.  Regular watering in the greenhouse may have served to reduce the presence of the mycelium as all treatments had minimal mycelium.  In future, digital image analysis will be utilized to measure treatment differences.  This methodology appeared to be effective for the determination of mycelium (Table 2).

Although at times there were mushrooms present, mushroom counts were not significantly different between treatments.  It is not known what factors trigger mushroom production and whether this will be a reliable method for the determination of effective treatments (Table 2).

Verdure is described as all above ground living material.  Plants were clipped to the thatch layer and treatments that had significantly better verdure than the untreated control were 0.416 litres/m², 0.833 litres/m², 1.665 litres/m², 6.666 litres/m², 13.32 litres/m² and 39.96 litres/m² (Table 2).

Table 2 - Ratings of Ultra Fairy Ring Solution for various dates.

      * Values that have the same letter as a suffix are not significant from each other

Soil moisture content was significantly higher than the untreated control in the following treatments: 1.665 litres/m², 26.64 litres/m², and 53.28 litres/m².  The Ultra Fairy Ring Solution product increased moisture content in the soil for some treatments and was related to an increase in area cover (Table 3).

Area cover ratings were determined by the NTEP rating scale as well as digital imaging analysis.  Treatments that were applied at 1.665 litres/m² and 13.32 litres/m² produced area cover ratings that were significantly better than the untreated control (Table 3). 

Table 3 - Ratings of Ultra Fairy Ring Solution for various dates.

                         * Values that have the same letter as a suffix are not significant from each other

Bibliography

Blenis, P.V., L.B. Nadeau, N.R. Knowles, and G. Logue.  1997  Evaluation of fungicides and surfactants for control of fairy rings caused by Marasmius oreades.  HortScience 32(6):1077-1984.