Bentgrass (Agrostis palustris) is an invasive, perennial grass often found in mild climates. While it is used in some areas as a lawn grass, its need for frequent fertilization and mowing makes it a more common choice for golf courses. Bentgrass, with its invasive nature, can quickly take over a lawn or garden. The type of herbicide used to eliminate bentgrass is generally based on whether or not there are other plants among the bentgrass that you wish to keep.
Glyphosate, commonly sold as Monsato Roundup, is a post-emergent, non-selective herbicide. Glyphosate is effective in killing bentgrass, but, as it is non-selective, it will also kill any other plants it comes in contact with. This herbicide is an effective choice when killing large areas of bentgrass in which no other desirable plants exist. Glyphosate is applied directly to the bentgrass, via a hand-held sprayer or tank, in dry conditions with little to no wind. There must be no precipitation for 48 hours after application for this herbicide to be effective. To kill only select patches of bentgrass growing among other, desirable plants glyphosate can be mixed in a small batch and applied with a paint brush only to the bentgrass. Caution must be used not to let the glyphosate soak into the soil or come in contact with the leaves of surrounding plants. An area can be re-seeded one week after glyphosate has been applied.
Fusilade is a post-emergence, selective herbicide that is safe to use in the elimination of bentgrass growing among other, desirable plants. It can be applied directly over an area and it will only target the grass, not any broad-leaf plants. For best results apply fusilade in the spring, to young bentgrass, during the cooler, morning temperatures. Fusilade is only effective when the bentgrass is actively growing, so it is not recommended to apply fusilade during extended periods of drought. Growth of the bentgrass should cease two days after application.
Envoy is a selective, post-emergence herbicide that targets both annual and perennial grasses. It, too, must be applied to the bentgrass during active growth, so avoid applications during drought. Apply Envoy directly onto the area when no precipitation is forthcoming for at least one hour. Results of the Envoy on bentgrass is visible in one to two weeks after initial application, though a second application is often needed to eradicate bentgrass entirely. If a second application is required wait two to three weeks after the emergence of new bentgrass before reapplying.