Be sure to read the label and determine how much time after application before an irrigation can be applied. Do not apply if rainfall is expected within 24 hours of application. Glyphosate works most quickly when the weather is warm and sunny. Activity may be delayed if it is cool or cloudy following application. MSMA is also translocated and must be applied to actively growing plants younger than the fifth-leaf stage.
Pelargonic acid is also most effective when applied on a warm, sunny day.
This chemical will not be affected by rain 2 hours after spraying. Because pelargonic acid does not move through the plant, you need to thoroughly cover the entire aboveground portion of the plant with spray to kill it. Halosulfuron is used in such minute amounts that the manufacturer markets it in premeasured, water-soluble bags. Follow all label directions for optimal control of nutsedge, and be sure to add a nonionic surfactant to the spray solution. Of these, metolachlor is more effective than EPTC and safer around many ornamentals than dichlobenil, but it must be applied by a licensed pesticide applicator.