Thursday, August 27, 2009

Turf and Landscape - Weed Seed Bank

With the ample moisture provided by recent rains, I see many turf areas and landscapes with weeds going to seed at this time. This will add to the weed seed bank and make weed management more challenging in the future. The following is more information.

Weed Seed Bank is a term used to describe the reservoir of viable weed seeds on the surface or in the soil profile. One major weed management goal in turf and landscapes should be to reduce the weed seed bank. Late summer is a major challenge because many weeds such as crabgrass are going to seed, especially in low maintenance areas. This adds to the weed seed bank and will make future weed control more challenging. It takes several years with no additions to the seed bank to reduce weed pressure. This is because of dormancy mechanisms allowing some weed seeds to remain viable for years.

The key to managing the weed seed bank is to not let weeds go to seed. For crabgrass, to get a 75% reduction in the seed bank, it will take 3 years of active control measures making sure there is little seed head production. To reduce weed seed head production in turf, mow more frequently using very sharp blades. This is especially critical in late summer. One challenge is low growing weeds that produce seed heads below the height of mowing. Herbicides will be your best option in that case (for large multi-tillered crabgrass use quinclorac – Drive herbicide). There are also some growth regulators registered for seed head suppression in specific weeds such as annual bluegrass.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

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