Dimension 2EW Herbicide will stay in the soil up to two years. It will be unsafe for the animals to graze until after the Dimension has left the soil.
Dimension 2EW is labeled to control poa annua (annual bluegrass) before it emerges and should do a good job when applied at the right time. Please refer to the product label for complete instructions. If you are already dealing with Poa Annua, you will need to use a post-emergent, and we do carry several. Which you choose depends on your grass type. Certainty is a good choice, but please refer to the label to ensure it can be used on your lawn type.
In Arizona, you would generally make two applications of Dimension 2EW Herbicide 5 to 10 weeks apart. We would recommend the Program 2 or 3 rates of 1 oz per 1,000 sq ft and then 1.5 oz per 1,000 sq ft, or 2 applications of 1 oz per 1,000 sq ft each, according to the product label. Be sure that you immediately water-in the application with a high volume of water any time there is a barrier like gravel over the ground. This will help get more of the active ingredient down to the soil so that it is not just absorbed into the rocks before it can reach the dirt. (Since this product is still intended to be used around turfgrass and ornamentals, you may not get the same results on a stone area.) At the 1 oz,1000 sq ft rate, you would use 0.22 oz of Dimension 2EW in 1 gallon in your sprayer to cover 220 sq ft.
We would not recommend applying herbicides such as Dimension 2EW Herbicide during active precipitation. Instead, you could use a higher volume of water, or you could irrigate the application yourself with at least 1/2 inch of water.
Whether oryzalin or dithiopyr is the best choice for you will depend on what weeds you are targeting, where you need to apply the product, and what price point you are wanting. Dithiopyr, which is the active ingredient in Dimension 2EW Herbicide, is the preferred pre-emergent for crabgrass and also covers a variety of other grassy and broadleaf weeds. Dimension also has the unique quality of offering early post-emergent control of crabgrass. Oryzalin (Surflan) is economical and can be used in some areas where Dimension may not be able to be used. Always be sure to check the product labels for whether the product you want to use is appropriate for your needs and safe to use around your target areas. Please let us know if we can further assist you.
The program that is chosen will depend on how long Dimension 2EW Herbcide lasts in the soil. For example, if Program 1 is done, it will provide 3-5 months of pre-emergent control. Most pre-emergent products will have to be applied at least twice a year to prevent Spring and Summer weeds.
Dimension 2EW is one of our most popular pre-emergents for crabgrass as well as many other broadleaf weeds, and it can safely be used on St. Augustine grass. Please check the product label to ensure that it will control the other weeds that you are targeting.
For long term control though, you should apply a pre-emergent in the late fall and early spring which will prevent new crabgrass from coming up next year. If you apply pre-emergent every year, you should not have issues with crabgrass long term. Dimension 2EW is one of our most popular pre-emergents for crabgrass.
Dimension 2EW which contains dithiopyr is labeled for use on carpetgrass.