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Treating Crabgrass Early Season

University of Minnesota Extension, Stearns County News
April 19, 2017        
Source:  Beth Berlin, Extension Educator-Horticulture
University of Minnesota Extension
Stearns, Benton, & Morrison Counties

Treating Crabgrass Early Season
By Beth Berlin, University of Minnesota Extension

ST. CLOUD, Minn. (4/19/17) — Depending on what part of Minnesota you are in this may be the optima time to apply your crabgrass pre-emergent herbicide.  However that window is short and for some it may already be over.  Visit provided by the Department of Crop and Soil Sciences, Michigan State University.  At this site you can simply enter your zip code and a map will indicate either "under, close, target, over, or done" for your area.

What is a pre-emergent herbicide?  First off, an herbicide is a chemical, organic or synthetic, that will kill plants.  Depending on the type of herbicide, they may be non-selective and impact all plants.  Other herbicides are more selective such as killing a grass or broadleaf plant.  Some herbicides are post-emergent and work when they come in contact of an existing living plant, impacting only the plant parts they come in contact with. Other herbicides are systemic which are taken up by the plant and impact all parts above and below ground.

Finally herbicides that are labeled a pre-emergent herbicide prevent seeds from being able to complete the germination process.  Therefore to be effective they need to be applied before seeds germinate. Often these products are applied to the soil, commonly as a dry granular but sometimes as a liquid spray and then are watered into the top one-inch of soil.  This typically requires about one-half inch of water after application.  A pre-emergent herbicide works when a sprouting seeds comes in contact with the herbicide.  The plant's cells divide for root system development but this is inhibited due to the pre-emergent herbicide which results in death of the young seedling. Obviously, this is not effective if the product is applied after the target window and soil temperatures are warm enough for the crabgrass to germinate.

If you plan to apply crabgrass pre-emergent, now is the target time for a lot of central Minnesota, but very soon the optimal application time will be over.  Visit for your specific zip code and area.