Cool Weather Returns Disease Pressure Remains
September 19, 2008
Cooler, wet weather with periodic days of sunshine and moderate daily temperatures have been the general pattern observed recently throughout most of the Northeast Region. The cooler weather patterns are conducive to cool season turfgrass growth, but disease pressure still remains. Diseases typically associated with hot, humid weather like Pythium are behind us, but gray leaf spot (GLS) has been active recently and may stay active until the first killing frost. Surprisingly, a small outbreak of brown patch was recently observed in southern New Jersey and was likely due to a combination of recently fertilized turf (to promote core cultivation recovery) and high nighttime temperatures and humidity.
Dollar spot pathogens are quite active and will likely remain so for a few more weeks. Numerous chemistries can be used for dollar spot suppression, however, rotation between active ingredients and tank-mixing is recommended. Diminishing plant protectant supplies and/or expended budgets further complicate later summer/early fall disease prevention strategies. Reducing leaf wetness duration via dew removal (mowing or dragging) is an invaluable mechanical practice for limiting dollar spot disease pressure. Dollar spot also will be more problematic on nitrogen deficient turf and outbreaks may be an indication that previous fertilizer applications are at the end of their release curve.
Disease pressure in September and October is certainly not as high compared to July and August, however, organic matter production via plant growth is accelerated and can increase summer disease pressure. Topdressing should be continued during the autumn months to dilute accumulating organic matter. Do your best to topdress frequently this year to maintain root zones with good soil physical properties. Ultimately, this will reduce disease pressure and physiological stress potential.