Surflan AS Herbicide can be tank mixed with 2,4-D following the instructions on each product label regarding doing so and rates.
Surflan AS Herbicide is toxic to fish. Do not apply directly to water, to areas where surface water is present or to intertidal areas below the mean high water mark. Do not contaminate water when disposing of equipment washwaters. Please refer to the product label for specific application instructions and the SDS for additional safety information.
Surflan AS is safe for animals when used as directed on the product label. People and animals should be out of the area while it is being applied but can safely return once the area is fully dry (usually a couple of hours).
For best results, Surflan AS Herbicide should be applied before soil temperatures reach 55 degrees or higher. It would be a good idea to contact your local cooperative extension office for advice on the best time to apply in your region.
Surflan AS Herbicide is toxic to fish, so it should not be applied directly to or near water. We would recommend that you apply at least 25 feet away from the stream, or any water source, as the active ingredient in this product can move throughout the soil. Please refer to the product label for specific application instructions.
Surflan AS Herbicide is a pre-emergent herbicide and will not eliminate any actively growing weeds.
Mixing a post emergent like 2,4-D with Surflan AS Herbicide would only be beneficial if you need to treat actively growing broadleaf weeds. Otherwise there would be no additional pre-emergent benefit.
No, Surflan AS Herbicide, does not require a surfactant to be mixed with it for spraying.
Surflan is a pre emergent herbicide that can be used in the listed turf grass species on the product label to prevent weeds such as barnyardgrass from coming up. Since none of the turf types you listed you have are on the Surflan label we cannot say for certain if it will harm your Switchgrass, Big Bluestem and Indiangrass. For your convenience I have copied the turf label instructions for you below.
"Warm Season Turfgrasses: Surflan Pro may be applied as a preemergence treatmetn for control of annual grasses and certain broadleaf weeds in established warm season turf including bahiagrass, bermudagrass, buffalograss, centipedegrass, st. augustinegrass, zoysiagrass, adn established tall fescue growing in warm season areas. Established turf is defined as a dense turf having a well-anchored root system and healthy, vigorous top growth. "
Surflan is not recommended to use on cool season turfs such as Kentucky Bluegrass which you also mentioned you had.
As far as a post emergent product to control the barnyardgrass goes, there are not any selective herbicides I can find that will control barnyardgrass without possibly also harming the other desired grass species you mentioned. You would have to spot treat the areas where the barnyardgrass is a problem with something like roundup or another herbicide labeled for barnyard grass control and then overseed with any other desireable turf in that area.. If you prefer to spot treat with something other than roundup a suitable product would be Quinclorac 75 which I have copied a link to below.
Quinclorac 75
https://www.domyown.com/prime-source-quinclorac-75-df-select-herbicide-p-12205.html
The amount of Surflan AS Herbicide you will use per acre will depend on the area that you are treating. For broadcasting on warm season turf, you will use 1.5-2 quarts per acre. For landscape, field-grown, and container-grown ornamentals, the rate is 2-4 quarts per acre. Please refer to the product label for complete application instructions.
Per the product label for Surflan AS Herbicide: Reseeding should be delayed for at least 90-120 days following application.
Surflan AS Herbicide is not for use in any crops for weed prevention and is only allowed in listed areas on the product label. You may want to reach out to your local state department of agriculture to find a product labeled for what you are trying to prevent in your oats and what other farmers in your area may be using.
No Surflan AS Herbicide can be applied to the following areas only: Landscape ornamentals, container grown ornamentals, field grown ornamentals, ornamental bulbs, ground covers/perennials, Christmas Tree plantations, Non-bearing fruit and nut trees and non-bearing vineyards, noncropland industrial sites. Warm-Season Turf: Bermudagrass, Bahiagrass, Buffalograss, Centipedegrass, St. Augustinegrass, Zoysiagrass and Tall Fescue. We do offer selective pre-emergent herbicides for Tall Fescue lawns.
Surflan AS Herbicide and other products with that active ingredient have been discontinued. A good alternative would be Pendulum 2G which is labeled for both sandbur and lawn burweed.
Surflan AS Herbicide is not labeled to control bedstraw. (Keep in mind that Surflan AS has been discontinued, so you will not be able to purchase this product if you do not already have it.) If you have existing bedstraw to control, then you can use a broadleaf post-emergent herbicide such as Prime Source Triad SFZ Select Herbicide.
The only pre-emergent active ingredient we are finding for any kind of galium is dithiopyr (Dimension 2EW) which is labeled for galium odoratum only.
