Chemical weed control
Chemical weed controls are more commonly called herbicides. They can be in liquid or granular forms. Using granular (i.e. weed & feed type fertilizers) the lawn should be wet (early morning dew is ideal) so the granules stick to the leaves.
Herbicides are divided in several classifications
Selective: A selective herbicide controls certain plant species without seriously affecting the growth of other plant species. The majority of herbicides used are selective herbicides.
Nonselective: Nonselective herbicides control green plants regardless of species. These are generally used to kill all plants, such as in the renovation or establishment of a new turf area, for spot treatment, or as a trimming material along sidewalks, etc. Glyphosate (Roundup®), Glufosinate (Finale®), and Diquat (Reward®) are examples of nonselective herbicides. are examples of nonselective herbicides.
Contact: Contact herbicides affect only the portion of green plant tissue that is contacted by the herbicide spray. These herbicides are not translocated or moved in the vascular system of plants. Therefore, these will not kill underground plant parts, such as rhizomes r tubers. Contact herbicides often require repeat applications to kill regrowth from these underground plant parts. Examples of contact herbicides include the organic arsenical's (MSMA, DSMA), bentazon (Basagran®), glufosinate (Finale®), and diquat (Reward®).
Systemic: Systemic herbicides are translocated in the plant's vascular system. The vascular system transports the nutrients and water necessary for normal growth and development. Systemic herbicides generally are slower acting and kill plants, over a period of days. Examples of systemic herbicides include glyphosate (Roundup®), 2,4--Dichlorophenoxyacetic acid (2,4-D®), dicamba (Banvel®), imazaquin (Image®), and sethoxydim (Vantage®).
Herbicides are useful, effective tools in the control of weeds in turf areas. Product labels should always be read and followed when using a herbicide, or any other pesticide. Herbicides are not a miracle cure, as they provide only short-term relief from weeds. The best approach is an integrated regime of proper mowing, fertilization, irrigation, and use of other cultural practices to maintain a vigorous turf.
Weed & Feed type fertilizers
There are some fertilizer products that have been combined with herbicides for broadleaf control, crabgrass control, and some combined with insecticides and fungicides to control insects and diseases.
The Weed & Feed products are designed to provide the right amount of fertilizer for specific grasses and control certain weeds such as broadleaf weeds or grassy-type weeds such as crabgrass. Each type of fertilizer is applied differently.
Pre-emergent fertilizers are used to control weeds before they sprout.
Fertilizers that control broadleaf weeds (i.e. Scotts' Turf Builder Plus 2) are used to control broadleaf weeds that are actively growing. Pre-emergent weed & feed fertilizers (i.e. Scotts' Halts) will not control actively growing weeds.
Combinations not only save considerable time, work and headaches, they also reduce the amount of material you need to use. You may even save money by buying one product instead of two or more.
However, timing can be tricky. The best option is to apply during growth cycles for the problems you want to stop, and follow directions carefully. These directions will tell you when to apply the product for your specific grass type and region of the country.
Watering Before or After Application of Weed Control Products
Weed controls including those that are both a weed control and fertilizer, should be applied according to label directions. You'll also note when reading the directions that certain products have different watering requirements, especially for granular type products. Typically with broadleaf weed controls the lawn should be watered immediately before application of granular products. The reason for this is that the granules must stick to the leaf to be effective. Liquid weed controls need a period of time without water after application to allow for the product to be absorbed through the leaves. Pre-emergent applications used to control crabgrass should be watered after application so the granules can be dissolved to create a barrier on the soil.
St. Augustine, Centipede, Zoysia and Carpetgrass
There are special weed & feed type fertilizers specifically for these grass types.
For use on St. Augustinegrass (including floratam), centipede, zoysia and carpetgrass lawns only
Builds thick, green turf from the roots up without burning your lawn
Kills dollarweed and other common lawn weeds including dandelions, chickweed, oxalis and more
Also prevents germination of crabgrass, bahiagrass and spurge
Apply only when grass is dry.
Set Spreader: See the back of the bag to determine the appropriate setting for your spreader.
Fill Spreader: Pour product into the spreader over bare ground or a hard surface. Be sure to clean up any spilled product.
Apply Product: Apply fertilizer carefully, avoiding hard surfaces like driveways and streets.
Water-in: Water lawn after application to activate the product. In temperatures above 80° F, water immediately after application.
Clean-up: Sweep product off driveways, sidewalks and streets. Return any unused product to the original container.