WEST LAFAYETTE, Ind. - As many of us have learned from our observations over the past few weeks, this was a great winter for snow mold development. Incidence of both pink and gray snow mold is evident in taller mown grasses in roughs, lawns and professional landscapes. Except in the northern-most parts of Indiana, only pink snow molds appear to be affecting creeping bentgrass greens, tees and fairways.
Obviously, the snow mold fungi are active at low temperatures. Gray snow mold (caused by Typhula incarnata) may be active at temperatures ranging from 30 to 40 F and require the moisture and the insulating effect provided by extended periods of snow cover. The pink snow mold fungus (Microdochium nivale) has a much broader range of temperatures (35 to 55 F), requires ample moisture, but snow cover is not necessary. Both types of snow mold result in tan-gray patches of dead, matted leaf blades. Distinguishing between the two snow molds involves close examination of the affected leaf material. The gray snow mold fungus produces small red-orange-tan structures (about the size of a period printed on this page) on surfaces of affected plants. No such structures are associated with pink snow mold.
By mid-March, the threat of damage associated with gray snow mold is greatly diminished. The turf will recover naturally, but raking the affected areas to break up matted grass blades will hasten recovery. Pink snow mold may be active through April and May. During extended periods of cold wet conditions, the pink snow mold pathogen will produce spores at the patch margins. The spores may be dislodged by splashing rain or surface water and dispersed away from the original patch. They often create new infections and may result in significant disease spread during spring months. On creeping bentgrass/annual bluegrass putting surfaces, new infections occur down-slope from the original pink snow mold patch, creating streaks of symptomatic turf on the green. The pink snow mold pathogen also may produce abundant mycelium on cool humid mornings.
What to do now? Encourage recovery of affected areas once warm weather arrives and the grass breaks out of winter dormancy. Light raking now will help break up the crusty patches, drying out the area, and potentially reducing further infection. Light fertilizer applications (0.1-0.5 lbs N/1000 ft2) may help recovery when applied after green-up, but don’t overdo the nitrogen rates because you will increase mowing needs now and you may reduce summer stress tolerance later.
Serious pink snow mold infections may weaken turf and impede its recovery during spring. On golf courses, this provides a perfect opportunity for germination and encroachment of Poa annua. Therefore, limit Poa establishment with an application of a preemergence herbicide early this spring. Since Poa annua can germinate quickly with warming soil temperatures, consider applying the herbicide as soon as possible. Our research shows that applying preemergence herbicides in early spring (March) will generally not compromise season-long control of crabgrass. Most currently available preemergence herbicides are labeled for preemergence control of Poa annua.
The same principles apply for higher mowed rough and lawns where crabgrass is a potential problem. Snow mold damage may slow recovery and fill-in of the desired turf, creating a perfect opportunity for crabgrass infestation. In lawns or rough with substantial snow mold damage, consider applying a preemergence herbicide this spring. The application for crabgrass does not have to be as early as the application made to control Poa annua, but it should be applied by late March in southern Indiana and mid-April in northern Indiana. Check with your local horticultural extension office for the appropriate application time in your area. As mentioned earlier, early applications of preemergence herbicides do not compromise season-long control so be sure to error on the side of being too early than too late.
Golf course superintendents are the primary users of fungicides for snow mold control. There are several fungicides that are effective in preventing snow mold development. PCNB (used under a variety of trade names) is most often used as a protectant applied prior to snow cover in late fall or early winter. Other fungicides, including Banner Maxx, Bayleton, Cleary 3336, Chipco 26GT, Curalan, Daconil and Eagle, may be applied during a late winter or early spring thaw to suppress pink snow mold development through the spring months. An application now may be justified to limit pink snow mold damage in the upcoming months.
Rick Latin is professor of plant pathology, Purdue University, and Zac Reicher is assistant professor/extension turfgrass specialist, Purdue University, and associate director of MRTF.
Reprinted with permission from the Midwest Fact Sheet, March 2001, published by the Midwest Regional Turf Foundation of Purdue University (MRTF). For more information about MRTF visit www.agry.purdue.edu/turf/mrtf.htm.
Sponsored Content
A Secret Weapon for Growing Your Lawn Care Business
Retargeting ads allow you to re-engage visitors who leave your lawn care website without converting, helping you stay top-of-mind and increase leads. This article explains how retargeting works, why it’s effective, and how to implement it for your business.
Complete Online Marketing Solutions
