Cold, rainy, windy conditions playing havoc on fall applications – Turfgrass Science at Purdue University

Cold, rainy, windy conditions playing havoc on fall applications

The window for effective broadleaf weed control is closing fast and we normally see good control of difficult-to-control weeds like ground ivy until about the end of October. However, you may still get adequate control of easier-to-control weeds like dandelion through the first week of November or as long as daytime highs are 50F or greater with ample sunlight. Therefore, applications made this week should still be effective when evaluated next spring even though leaf curling will likely not be seen anymore this year. To increase speed of control, consider adding QuickSilver (carfentrazone) or using a product that contains carfentrazone.

Conversely, we are still in the middle of the effective window for late fall fertilization. All cool-season turf areas should receive a final application of N at 1.0 to 1.25 lbs N/1000 sq ft. This application is most effective with fast release N like urea or ammonium sulfate applied when the grass is still green and actively photosynthesizing. The nitrogen has to be taken up immediately to be effective (see the previous Turf Tip on how this works). Applications made to dormant turf, frozen soils, or otherwise plants not actively photosynthesizing are not recommended.

On golf courses, parks, or large properties not on an annual contract, late fall applications of preemergence herbicides can provide season-long control of crabgrass next year. Applications now are convenient because they can be combined with the final application of nitrogen and also free up labor next spring when it’s needed for mowing. The highest recommended rate should be used and if sequential applications are typically used, the sequential application can be made at the typical timing next summer.


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