5/20/2010 - By Harrell's

Laurence Mudge, Technical Service Lead, Bayer Environmental Science

Cool start to 2010

2010 started out colder than normal in many parts of the United States, particularly in the southeast. The three month outlook from the national weather service (www.nws.noaa.gov) is predicting below normal temperatures for much of the southeast and transition zone. Weather patterns indicate this could be the year that significant winterkill of bermudagrass occurs in parts of the transition zone on golf courses.

Winterkill

Winterkill is a general term used to define turf loss during the winter/early spring and can be caused by a combination of factors including: low temperatures (direct freezing of the plant), ice sheets (plant suffocation), crown hydration (rupturing) or dehydration (drying), plus diseases (e.g., spring dead spot and snow mold). Due to changes in environmental parameters, and differences in other factors such as surface drainage and wind patterns, the occurrence of winterkill is unpredictable, and can vary greatly. In addition, diseases such as spring dead spot can be more severe in colder winters.

Winterkill is hard to predict and many factors play a role in how bad it will affect your turf in a given year, including:

• Freezing temps, especially in late winter
  • Premature greenup followed by cold temperatures
• Varying soil moisture levels
  • Excessive moisture
  • Drought conditions
• Weak turf quality going into colder temperatures caused by:
  • Shade
  • Traffic
  • Low fertility or pH

Renovation

If your turf is affected by winterkill and affected areas require some type of renovation, such as sodding or sprigging, then preemergent herbicide selection is an important consideration. Certain preemergent herbicide active ingredients, such as prodiamine, pendimethalin, and dithiopyr, control weeds effectively by inhibiting cell division in the roots of germinating weeds. These types of herbicides can negatively affect rooting of desirable turf and limit the ability for the bermudagrass to tack down and fill in. Lateral spreading of bermudagrass stolons can be negatively affected.

Preemergent Herbicide Selection

Preemergent herbicides are often applied prior to really knowing how bad the winterkill is. Bermudagrass starts to green up in the spring after preemergent herbicides have been applied and that is when winterkill really becomes apparent. Ronstar® (Restricted Use Pesticide) has a unique mode of action that works through the shoots and has no effect on rooting, so you can be assured that if you have winterkill issues, your bermudagrass renovation activity will not be affected by root inhibition. In addition, Ronstar (Restricted Use Pesticide) provides outstanding control of both crabgrass and goosegrass. If you do not overseed your course, then Ronstar (Restricted Use Pesticide) Flo would be a great option. It can be easily tankmixed with your wintertime cleanup applications of Finale, Revolver, or glyphosate.

Renovation Tips

If renovation is required, other steps to consider include:

• Determine which variety of turfgrass to establish during the renovation process and contract with your preferred turfgrass supplier for a quantity of grass to complete the renovation process, visit the turfgrass farm, and select and/or approve the turfgrass selected.
• Ascertain the equipment and financial requirements needed to complete the renovation process and budget accordingly. Advise membership of the upcoming conditions and necessary renovation steps.
• Strategically plan your fertilization program to promote optimum grow-in conditions for the renovated turfgrass. Fertility should be based on soil sample recommendations to provide a well-balanced growth response between turfgrass roots and leaves.