Post emergent crab grass killer
What would be the best time to apply post emergent crab grass killer this year?
Anne Arundel County Maryland
Post emergent crab grass control is normally applied when the weed is quite visible and actively growing. However, it is still possible for you to apply a pre-emergent crabgrass preventer. In our area, we recommend a first application when the forsythia blossoms begin to fall from the plant and a second application about six weeks later. There are several products available and most of them are effective, but read the label carefully before purchase and before application.
First, thank you so much for your help on this. In regards to the Forsythia Blooms, please clarify that this is in relation to the pre-emergence crab grass killer.
While it may seem strange, it is in relation to the forsythia blooms. Given the unpredictability of the weather, it's impossible to give a firm date for application each year, but the forsythia bloom always coincides with the germination of crabgrass, so it is a good bio-indicator of timing.
OK. So I apply the first application of POST emergent crab grass killer when the Forsythia Blossoms begin to fall?
Crabgrass is best controlled by applying a preemergent in the spring. Apply the preemergent crab grass herbicide when the forsythia blooms begin to fall. If crabgrass pressure is heavy, a second application may be necessary 6 weeks after the first. Read the product label for important information regarding application and make sure the product you select does not contain fertilizer!
As mentioned above, a postemergent crabgrass killer can be used to treat crabgrass AFTER it has emerged with a crabgrass control and the weed is young. Once it matures and becomes larger herbicides are not effective.
See our publication for more information on crabgrass https://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/tt-43e-crab.pdf