Effective Lawn Weed Management

Published 7:00 am Saturday, March 1, 2014

By Eddie Smith

Co. Coordinator ANR & CRD Agent MSU-ES Pearl River County


For effective lawn weed management, February-March is the time to take action in controlling existing winter weeds, such as clovers, wild garlic, henbit, chickweed, etc., with post emerge herbicides. It is also the time to apply pre-emerge herbicides to prevent annual weeds, such as crabgrass, goose grass, spurges, etc., from infesting the lawn through spring and summer.

February-March is also an ideal time to apply post-emerge herbicides since most warm-season turf species are somewhat dormant and less likely to be injured by the herbicides. The winter weeds are actively growing and have not been mowed, so there is ample leaf area to absorb the herbicides for effective control.

There is also some efficiency gained since both post-emerge and pre-emerge herbicides can be applied in the same application.

Fertilizer granules provide a simple and easy carrier to distribute pre-emerge herbicides that must be applied to our lawns prior to weed seed germination if the herbicide is to be effective. However, there is a downside to using many of these weed and feed fertilizers in the spring for our southern lawns.

Some of these fertilizer products containing pre-emerge herbicides only are formulated with high nitrogen content for cool season turf species that can utilize the nitrogen at this time of the year. These fertilizers put on our dormant warm season turf species lawns now will most likely feed existing winter weeds. And those weeds will compete for space when our lawns begin their flush of spring growth unless a post-emerge herbicide is also applied.

With too early high nitrogen fertilization, you may also be setting your lawn up for cold injury from a late season freeze.

Therefore, my suggestion is if you use a weed and feed fertilizer as a carrier for your pre-emerge herbicide, try to find a fertilizer formulation that is low in nitrogen or one that the nitrogen source is in a slow release form.

Most southern lawns can wait until they have gone through spring transition and have been mowed at least twice before applying spring nitrogen fertilization.

With any pesticide, you should always read the label carefully and completely before applying.

The herbicide label will provide a list of where it can safely be applied and the weed species the active ingredient will control and at what rate.