How to kill St Augustine in Bermuda Grass

I used to have a lawn that was mixed with St Augustine and Bermuda grass. To kill the St Augustine, there are a few things you can do.

Kill St Augustine in Bermuda grass

Cut Low

The easiest thing you can do is to mow lower. St Augustine hates low HOC (height of cut). Use a reel mower to mow at an inch or lower, and you’ll find the Bermuda thriving.

Selective Herbicides

Quinclorac is a cheap and effective chemical for crabgrass. However, it’s not safe on St Augustine. You can spray Quinclorac on your entire lawn and it will harm the St Augustine but not the Bermuda. However, there are a handful of herbicides that fit the bill.

  • 2,4-D: Effective on Bermuda grass for broadleaf weed control; can damage St. Augustine grass, especially at high temperatures.
  • MSMA (Monosodium methanearsonate): Targets grassy weeds in Bermuda grass; not recommended for use on St. Augustine due to potential injury. Do not use on residential lawns, particularly if you have pets.
  • Dicamba: Used selectively in Bermuda grass for broadleaf weed control; can harm St. Augustine grass if not applied correctly.
  • Quinclorac: Effective for crabgrass and other broadleaf weed control in Bermuda grass; may cause damage to St. Augustine grass.
  • Sethoxydim: Controls grassy weeds in Bermuda grass; not safe for use on St. Augustine grass as it can cause significant injury.
  • Tribute Total: Tribute Total can effectively kill St. Augustine grass. Tribute Total is a herbicide that’s primarily used for post-emergence control of grassy and broadleaf weeds, and it’s very potent against many types of grasses, including St. Augustine.

Reduced Watering

Bermuda grass is more drought-tolerant than St. Augustine grass. Reducing irrigation can stress St. Augustine grass without significantly affecting Bermuda grass.

Solarization

During the hottest part of the summer, use clear plastic sheeting to cover areas of St. Augustine grass in your Bermuda lawn. The increased temperature can kill St. Augustine grass and its seeds.

Kill Bermuda grass in St Augustine

To kill the bermuda in St Augustine, you can wait for the St Augustine to go dormant. St Augustine will be dormant longer than bermuda grass typically. When the St Augustine is dormant and the Bermuda grass is not, you can apply glyphosate to the lawn. Since St Augustine is dormant, it won’t have any effect. However, the Bermuda grass will die if it’s not dormant.


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