Annual grassy weeds like crabgrass and foxtail will appear every year. They need sunlight and warm soil temperatures to do their thing. Prevention is the best strategy. Strong and vigorous grass and other plants will outgrow weeds.
Soil temperature at a constant 55 degrees and weed seeds will start to sprout. Putting on a product too early will likely reduce the effectiveness later in the season. Temperature and moisture will break down the product. There needs to be an adequate active ingredient to do the desired job.
In certain areas of the lawn, it is harder to have a thick stand of grass. Weeds crowd in when grass is too thin or there is too much shade. Crabgrass and foxtail prefer full sun, so they usually aren’t found in the shade. They do like the hot full sun locations along the walks, curb and driveway.
Most crabgrass preemergence herbicides which prevent weed growth need to be in place around the time our redbud trees are in full bloom. Preemergence products require time to become active so that when weed seed germinates it will be effective. Irrigate with up to ¼ inch of water to activate all products.
There are options if you don’t get a product put down on time. You can go ahead and put down any of a number of preemergence knowing that there may be some weeds that may have beaten the application. These emerged grassy weeds can be treated with a labeled post emergent herbicide or cultivated out.
One product gives some post emergent along with preemergence control. That herbicide is called dithiopyr referred to as Dimension. It will kill already growing grassy weeds if they are still small, up to the third leaf. Dimension will then act as a preemergence to keep weeds from developing. One application per year is all that may be needed.
Homeowners have several post emergence herbicides available to manage annual grassy weeds. One of the most commonly found product is Drive (quinclorac) which is labeled for use on many of our turf grasses. I use a product called Tenacity (mesotrione) on my buffalograss. Existing weeds need to be actively growing to get good results.
When using an herbicide or any other pesticide, read the label first. You will get the best results by following the label directions. Besides, it is the law.
Eyestone can be contacted at 785-537-6350. His email is geyestone@ksu.edu.
