Bermuda Grass Weed Killer

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So what are the different types of weed killers or herbicides that you need to use to eliminate the weeds from Bermuda Grass? The answer really depends on the type of weed that has affected your lawn. Also, depending on the weed type, the herbicide application rate and timing can differ. Over application or wrong application can completely destroy your garden and you might have to start from the scratch again. Here are some proven guidelines for using weed killers on Bermuda grass. 
Remember that while weeds can be controlled even after they have germinated and emerged, it is always recommended to use appropriate herbicides or weed killers before the weeds have germinated (i.e. by using pre-emergent weed killers before the weeds have emerged). 
The pre-emergent herbicides need to be soaked into the soil so that the weed seeds can be destroyed. While for post emergent cases, you will need to only lightly spray the weed killer and mist the grass. 

Pre-emergent Bermuda grass weed killers

For the summer time crabgrass weeds, pre-emergent chemicals can be applied in spring when soil temperature rises to 60°F. Dimension (active ingredient being dithiopyr) is one of the best and safe pre-emergent herbicides to eliminate Crabgrass. A crabgrass preventer can also be used to control winter weeds like poa annua on Bermuda grass.  
For winter weeds like annual bluegrass, pre-emergent weed killers are applied in September or early October or even in November. The pre-emergent chemical should be watered while applying into the soil. 
Chickweed is another annual winter weed and can be controlled with a pre-emergent weed killer such as isoxaben (portrait). It can be killed with herbicides like  2-4-D amine and MCPP. These chemicals can be used on Bermuda grass that is not in dormant stage (that is not during winter time like January). 
Wild Onions that look like onion plants are weeds that can destroy a soft Bermuda lawn. They remain dormant as seeds or as bulblets under the soil. In spring, you can apply 2 sprays with either a non-selective weed killer (RoundUp, Finale) or a herbicide labeled for broadleaf weeds (Weed B Gon, Wipe Out, etc.) at six-week intervals. 
Another chemical imazaquin (Image) can also be used for the above purpose. Be careful while using these chemicals. When Bermuda grass is coming out of winter dormancy, they can be quite harmful. They are also harmful to newly planted or sprigged turf grasses. 
Other pre-emergent herbicides like Karmex is also used to remove Bermuda grass weeds. 
To control broadleaf weeds, another herbicide 2-4-D amine can be used, but after spring.  
It is generally not a good idea to use pre-emergent weed killers while seeding and establishing a Bermuda grass lawn. Pre-emergent application can also prevent the winter rye grass seeds from sprouting. It's wise to consult a local nursery before applying pre-emergent product during grass seeding time.  

Post-emergent Bermuda grass weed killers

Post emergent chemicals are applied for the weeds that have already emerged. These weed killers are much more toxic than the pre-emergent ones and require light applications, generally one or two light sprays. For liquid herbicides, only light misting is required. 
The most common active ingredients that are applied for post-emergent cases are non-selective chemicals like Glyphosate or Glufosinate. These chemicals that are available as herbicides or weed killers, sip into the roots through leaves and retard the growth of the weeds.  
For example when Bermuda grass remains dormant in January, Glyphosate can be sprayed to kill fescue and other weeds. This chemical can be applied only during the time when Bermuda grass is dormant.  
For killing crabgrass, you can spray a chemical containing methanearsonate once or if required twice at an interval of two weeks. This should be done as soon as you see crabgrass weeds. 
In spring, the application of a non-selective herbicide (like RoundUp, Roots & All, Finale) on bluegrass weeds is the best way to kill it. This control measure can be taken only by a light spray on the foliage. 

General precautions while applying weed killers

Do not use a total vegetation killer like Triox that is a soil sterilant and has been already applied earlier. Triox can kill the persisting vegetation in the soil.  
There is a specific time for using a product like 2-4-D amine. It can be applied only when the temperature is low. During other time of the year, this product turns into gas and can cause damage to surrounding vegetation as it drifts through the air. 
Note that herbicides cannot be used on every kind of grass. Before use of any weed killer, you should follow the product label for safe and effective use. It is also important to have a good understanding of the weed type before using a chemical. Otherwise you may end up killing the entire lawn. 

Buying Bermuda Grass Herbicides

If you are located in the USA, you can go through this Amazon's Online Store which has a good collection of products related to Bermuda Grass weed killers including herbicides and related accessories. 

Related Articles

1) Check out Bermuda Grass Weed Control to know about all the different ways to eliminate weeds from the desirable lawn grasses. 
2) Check out Bermuda Grass to know all about Common Bermuda Grass.