Although the cool weather tends to limit disease in new seedlings, a spike in the temperatures could trigger outbreaks in juvenile turf yet this year. Late summer is clearly the best time of the year to seed for a variety of reasons, but we must deal with two difficulties of seeding at this time:
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Our driest months are usually Aug and Sep and thus irrigation is essential for success in a late summer seeding;
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Increased soil and air temperatures combined with high humidity and frequent irrigation create ideal conditions for seedling diseases like damping off, caused by Pythium (and other fungi) which can destroy a new stand virtually overnight.
Limiting these diseases can be done by:
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Watering in the morning and early afternoon to allow soil to dry as best you can before nightfall;
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Mowing as soon as seedlings reach a mowable height will tend to keep the canopy drier and less humid, which is less conducive to infection;
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Purchasing seed coating with Apron or other fungicides. These normally add about 7-10 cents/pound to the cost and will protect against infection at a very critical time. This is pretty inexpensive protection in our opinion.
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Treating seedbeds or newly emerged seedlings prior to the onset of warm wet weather with Subdue or Banol to avoid Pythium damping off and/or Pythium blight. One problem is allowing the seedbed to dry in order to support foot, spreader, and/or sprayer traffic. Small sprayers will likely be necessary and Subdue is available in a granular formulation.