Optimally to obtain the greatest benefits from organic pest control you should concentrate on creating an environment that encourages healthy turfgrass growth and discourages weed infestation and use natural, organic pesticides to control or manage the weeds such as corn gluten.
Corn gluten meal is a by-product of the wet milling process of corn for starch. It is also produced as a by-product during conversion of starch from dry-milled corn to corn syrup.
Pre-emergent control means that it inhibits the germination and establishment of new seeds. This product will not control existing established weeds, so it needs to be used over a number of years in order to achieve good results. The existing weeds will eventually complete their lifecycle and die, but new weeds will be slow to establish. If you are overseeding a lawn, do not use corn gluten until the new seed is established.
Spring and fall applications are best because this is when the majority of the weed seeds germinate.