UMass Extension Turf Program

Alternative Options to PCNB for 2011 Snow Mold Control

Date: 
September 12, 2011
Subject: 
Alternative Options to PCNB for 2011 Snow Mold Control
Category: 

Recently (8-19-11), the chief judge for the United States District Court for the District of Columbia granted the American Vanguard Corporation’s motion to vacate the Stop Sale, Use, or Removal Order of pentachloronitrobenzene (PCNB) that was filed by the United States Environmental Protection Agency last August, 2010.  The press release that announced this information can be found at the following location:

http://www.amvac-chemical.com/NewsMedia/PressReleases/2011PressReleases/August192011/tabid/153/Default.aspx

In brief, this means that PCNB will be available for sale for turfgrass us at some point; however, a timetable for the distribution of PCNB to the turf market has not been established.  Since the details remain unclear on availability, the best course of action is to contact your local sales representative for further information on availability.  Therefore, we are preparing advice for 2011 snow mold applications without PCNB.

We are dividing our 2011 snow mold information into two groups: low disease pressure (less than 90 days snow cover) and high disease pressure (more than 90 days snow cover).  The grouping designation was created because different snow mold species occur under different snow cover conditions.  Pink snow mold or Microdochium patch (caused by Microdochium nivale) can occur during the winter with or without snow cover or during cool (32-60 °F), wet periods when turfgrass growth is very slow.  This disease tends to be more prevalent in shady areas.  Areas that receive extended snow cover (90 days or more) are more likely to face damage from both gray snow mold or Typhula blight (caused by Typhula incarnata and Typhula ishikariensis) and Microdochium patch.  Both Typhula causal agents require snow cover to infect turfgrass and increase in severity proportionally with length of snow cover. 

Low disease pressure (less than 90 days snow cover)

For areas that face lower disease pressure (less than 90 days snow cover), snow mold applications should focus on controlling Microdochium patch and T. incarnata.  In general, applications that include multiple active ingredients at the highest label rates are the most effective.  If rates are reduced or one active ingredient is applied, some reduction in control can be expected.  Rates should be chosen according to the label and the importance of the turfgrass area.  Areas such as fairways can generally tolerate higher amounts of damage and taller grasses will recover faster from the damage.

Although the single active ingredients listed below are capable of controlling snow molds at various levels under low disease pressure, a single active ingredient for snow mold control, especially on putting greens, is not recommended.  Single active ingredients are appropriate for areas that have lower disease control expectations such as fairways and tee boxes.  This is entirely dependent on the amount of snow mold damage that can be tolerated.  Past experiences with snow mold control have shown that a single active ingredient will control snow molds under low disease pressure.  However, the amount and length of snow cover in New England is so variable that using a single active ingredient is like playing snow mold roulette. 

Fungicide classes or active ingredients are listed in alphabetical order:

  • Chlorothalonil
  • DMI (Fenarimol, Metconazole. Myclobutanil, Propiconazole, Tebuconazole, Triadimefon, and Triticonazole)
  • Fludioxonil
  • Flutolanil
  • Iprodione
  • Mancozeb
  • Polyoxin-D
  • Strobilurin (Azoxystrobin, Pyraclostrobin, Fluoxastrobin, and Trifloxystrobin)
  • Thiophanate-methyl

Two-way tank mix combinations are the best option for areas that face low disease pressure because they provide additional control during years when snow cover is longer than expected.  We strongly recommend the use of two-way tank mix combinations on putting greens and any areas in which the tolerance to snow mold damage is low. Tank-mix options are not listed in any sort of preferential order.

  • Chlorothalonil + Any of the active ingredients listed above
  • Fludioxonil + DMI (Fenarimol, Metconazole. Myclobutanil, Propiconazole, Tebuconazole, Triadimefon, or Triticonazole)
  • Iprodione + Strobilurin (Azoxystrobin, Fluoxastrobin, Pyraclostrobin, or Trifloxystrobin)
  • DMI (Fenarimol, Metconazole. Myclobutanil, Propiconazole, Tebuconazole, Triadimefon, or Triticonazole) + Strobilurin (Azoxystrobin, Fluoxastrobin, Pyraclostrobin, or Trifloxystrobin)

High disease pressure (more than 90 days snow cover)

For areas that face higher disease pressure (more than 90 days snow cover), snow mold applications should focus on controlling both gray snow mold and Microdochium patch.  Therefore, a multi-pronged approach is necessary and should utilize at least two different active ingredients.  Remember there are many different tank-mix options.  We are listing options that we have tested in the past and have observed good control.  There is a variety of ways to achieve the following tank-mix combinations (especially given the number of pre-mix products available).  In addition, two split applications (half rate) of the mixtures with 7-10 days interval  perform better than one single application of the mixtures (full rate).  Please feel free to contact Dr. Geunhwa Jung or Jay Popko if you have any questions regarding snow mold control strategies.

Most effective tank-mix combinations for high disease pressure (listed alphabetically):

  • Chlorothalonil + Iprodione + DMI (Propiconazole, Tebuconazole, or Triticonazole)
  • Chlorothalonil + Fludioxonil + DMI (Propiconazole, Tebuconazole, or Triticonazole)
  • Chlorothalonil + Strobilurin (Azoxystrobin, Fluoxastrobin, Pyraclostrobin, or Trifloxystrobin) + DMI (Propiconazole, Tebuconazole, or Triticonazole)
  • Chlorothalonil + Thiophanate-methyl + Polyoxin-D + DMI (Propiconazole, Tebuconazole, or Triticonazole)
  • Iprodione + Strobilurin (Azoxystrobin, Fluoxastrobin, Pyraclostrobin, or Trifloxystrobin) + DMI (Propiconazole, Tebuconazole, or Triticonazole)

For a listing of fungicides currently labeled to manage snow molds, refer to our current fungicide charts or Turf FRAC Tracker.

--

Submitted by: Dr. Geunhwa Jung and James Popko

Disclaimer

Archived Turf Management Updates contain information that is presented as it originally appeared, in an effort to preserve useful information and to illustrate changing management techniques and pest patterns over time. Some text may contain references to specific pesticide or fertilizer products. Due to the continually changing nature of the industry and pesticide regulations, some messages may contain references to products that are no longer available and/or are no longer registered for use.
View complete disclaimer