Biology of Microdochium nivale and Management of Fusarium Patch (pink
snow mold) in New England (and parts of New York).
Dr. Gail Schumann, University of Massachusetts, 2 years ($8,702, $6,702)
Objective(s): 1. Provide new information that would help those to better manage
Fusarium Patch (pink snow mold). 2. Fungicide Management including alternatives to
PCNB. 3. Biological Control possibilities. 4. Determine a disease prediction system and
understand conditions that lead to disease outbreaks.
Results: Project to begin Winter 2000 in conjunction with funding from MYSTA, MGCSA, VTGCSA, CAGCS, GCSANE, and GCMACC.
2000 Results: The purpose of the study is to improve management of Fusarium patch/ pink snow mold through a better understanding of the biology of the fungus that causes the disease, Microdochium nivale in the northeastern U.S. and through improved fungicide choice and application. It is becoming clear that a number of fungicide combinations are effective for winter-long control. It also appears that there is a far greater application timing window than previously thought. When fungicides are applied after top growth has ceased to leaf blades that are still green and capable of absorbing the excellent new systemic fungicides, a single application is likely to be sufficient at any time between the final mowing and before snowfall. Another fungicide timing study will be conducted in the winter 2001-2002 along with a superintendent's timing study. Data will be collected to help create a disease prediction system for Fusarium patch outbreaks in the spring and fall. Laboratory studies are in progress to determine the effects of temperature and pH on fungal growth and ability to cause disease. A fungicide resistence survey is also in progress. At this time, there is no evidence of resistance of M. nivale to the Q10/strobilurin fungicide group (Compass, Heritage). This survey will be continued for the other major fungicide chemical groups.
2001/2002 Results: Final Report
PROJECT: Biology of Microdochium nivale and Management of Fusarium Patch (Pink Snow Mold) in New England
PRINCIPAL INVESTIGATOR:
Gail L. Schumann
Dept. of Microbiology
209E Fernald Hall
University of Massachusetts
Amherst MA 01003-2420
(413) 545-3413
schumann@pltpath.umass.edu
EXECUTIVE SUMMARY
This purpose of this study was to improve management of Fusarium patch/ pink snow mold through a better understanding of the biology of the fungus that causes the disease, Microdochium nivale, in the northeastern U.S. and through improved fungicide choice and application. Contrary to common belief, it is clear that a number of fungicide combinations are effective for winter-long control. These include combinations of currently available commercial products, combinations with reduced rates of PCNB, and experimental products in development as commercial fungicides.
It also appears that there is a far greater application timing window than previously thought. When fungicides are applied after top (foliar) growth has ceased, but leaf blades are still green and capable of absorbing the excellent new systemic fungicides, a single application is likely to be sufficient at any time between the final mowing and before snowfall. In 1999-2000, a fungicide trial and timing study demonstrated only a few significant timing differences in control for fungicides applied on 11, 18, 28 Nov or 4 Dec. The 2000-2001 fungicide trial and timing study had no significant differences in disease control whether fungicides were applied on 12 or 28 Nov. In the 2001-2002 trial, a similar result was seen with applications on 12 or 18 Nov. These studies were all conducted to create severe disease pressure including inoculations with pathogens and high moisture from a greens cover for the entire winter. It is now necessary to test these results in the real world. Volunteer superintendents will split fairways or greens, apply their fungicides to each side on different dates, and evaluate them for snow mold in the spring.
Isolates of Microdochium nivale were tested for resistance to the major fungicide chemical groups [azoxystrobin (QoI/strobilurins), iprodione (dicarboximides) propiconazole (DMIs), and thiophanate-methyl (benzimidazoles] No fungicide resistance are observed, but two isolates spontaneously developed resistance during the experiments which suggests that this could easily happen in the field as well.
Laboratory studies of isolates of Microdochium nivale determined that they were biologically quite similar even though they were collected from throughout New England at a wide variety of times including just after snow melt and during spring and fall disease outbreaks. The isolates all belonged to the subspecies var. nivale. The optimal growth temperature range is 20-22.5oC (68-73oF) and the optimum pH range for growth is 5.8-6.3 in the laboratory. These are in marked contrast to the conditions that favor Fusarium patch/pink snow mold development in nature. Thus, the environmental factors that affect the pathogen also have an impact on the plant. Laboratory inoculation studies indicated that disease is more severe at 5oC (41oF) compared to 10oC (50oF) or 15oC (59o), as we would expect. It is likely that a dormant plant at low temperatures is unable to produce the same defenses as an actively growing one at higher temperatures. Due to the weather during the study, we were unable to obtain enough field environmental data to create a spring/fall disease Fusarium patch outbreak prediction system, but this would still be useful in the future.
CONCLUSIONS:
- There are many commercial fungicide combinations that are suitable substitutes for PCNB. There are also effective combinations with reduced rates of PCNB. A number of excellent experimental products may be available in the near future.
- Snow mold fungicides may be applied after foliar growth has ceased and before snowfall for winter-long snow mold control. This needs to be tested further on golf courses. It is important to apply the fungicides in sufficient water for good coverage (2.5 gal water/1000 sq ft is recommended).
- Fungicide resistance was not found to the 4 major chemical groups (benzimidazoles, dicarboximides, DMIs, and QoI/strobilurins) in the isolates tested. Resistance to azoxystrobin (Heritage) appeared spontaneously during the experiments.
- The isolates were biologically similar and caused the most severe disease at 5oC (41oF). Further field study of key environmental factors is needed to create a prediction system for spring and fall outbreaks of Fusarium patch.
Some chemical combinations that appear to be reliable from UMass research are:
Heritage 0.4 oz + Chipco 26GT 8 fl oz
Compass 0.2 oz + Banner MAXX 2 fl oz
Heritage 0.4 oz + Daconil Weatherstik 8 fl oz
Heritage 0.4 oz + Daconil Ultrex 7.5 oz
Heritage 0.4 oz + Daconil Ultrex 3.2 oz
Medallion 0.5 oz + Banner MAXX 3 fl oz
Chipco 26GT 4 fl oz + ProStar 3.75 oz
iprodione (Chipco) + chlorothalonil
Banner, Heritage, or chlorothalonil + reduced PCNB (8 oz)]
Heritage + Rubigan
Heritage + Fungo
Heritage + Banner
Banner + chlorothalonil
The general theme here is to use products from 2 different chemical groups, generally at the higher rates.
The New England Regional Turfgrass Foundation would like to thank Dr. Schumann and Richard Anair, Jr. of the University of Massachusetts for their work done on this study and the CAGCS, MeGCSA, GCMACC, NEGCSA, NYSTA and the VtGCSA for co-sponsoring this turfgrass research project over the last 3 years.
