We have received some calls inquiring about herbicide options for soybeans that have emerged, says Dwight Lingenfelter, but the field did not receive a burndown herbicide or a residual was not applied yet. Weeds like dandelion, resistant marestail/horseweed, etc. will be very difficult to control postemergence in soybean. Also, many of the typical soil applied residual soybean herbicides (e.g., Valor, Authority, Sharpen, metribuzin, etc.) cannot be applied over the top of soybeans because of injury concerns. Below is a list of herbicides that have foliar broadleaf activity and/or residual activity and are allowed POST along with their labeled application timings and strengths.

Unfortunately, most of these herbicides will not handle dandelion, burdock, curly dock, etc. very well, says the Extension Associate. Keep in mind that products such as Dual Magnum, Outlook, Warrant, and Zidua will not control emerged weed, so they will need to be tank-mixed with herbicides that have foliar activity.

Additional details about these herbicides can be found in Table 4-14 of the Mid-Atlantic Field Crop Weed Management Guide. This is not a comprehensive list and excludes generic products and herbicides that are mostly active on grasses and/or not typically applied POST.

Anthem Maxx—can be applied POST but the exact application timing is not specified but at least 60 days before harvest. Since it contains Cadet some annual broadleaves (not marestail) will be controlled during burndown but it tends to be weak on perennials. The pyroxasulfone (Zidua) portion will not control existing weeds but will provide residual activity on annual grasses and small seeded broadleaves.

Basagran—after emergence (general control of small annual broadleaves—good on cocklebur, lambsquaters, smartweed, and velvetleaf).

Blazer or Ultra Blazer—soybeans should have at least one to two trifoliate leaves (general control of small annual broadleaves—good on jimsonweed, pigweeds, nightshade, common ragweed, and smartweed).

Cadet—Preplant through full flowering (general control of small annual broadleaves—good on lambsquaters, nightshade, pigweeds, and velvetleaf).

Classic (or Synchrony)—at least one trifoliate leaf up to 60 days before maturity (general control of small annual broadleaves—good on cocklebur, jimsonweed, pigweeds, and smartweed).

Cobra—apply PRE or POST up to 45 days before harvest- one to two trifoliate leaves is typical (general control of small annual broadleaves—good on jimsonweed, nightshade, pigweeds, ragweeds, and smartweed).

Dicamba products (Engenia, Xtendamax/FeXapan)—for use in Xtend soybean varieties only; soybean emergence thru R1 stage. Controls many annual and perennial broadleaf weeds.

Dual Magnum—can be applied POST but the exact application timing is not specified but at least 90 days before harvest. It will not control existing weeds but will provide residual activity on annual grasses and small seeded broadleaves and nutsedge.

FirstRate—1st soybean trifoliate through 50% flowering (general control of small annual broadleaves—good on cocklebur, ragweeds, and velvetleaf).

Glyphosate (Roundup Ready only)—emergence through flowering. Overall good weed control of many species but it can be weak on perennials such as dandelion and glyphosate-resistant weeds such as marestail.

Harmony SG—after 1st trifoliate has expanded fully and no later than 60 days before harvest (general control of small annual broadleaves—good on lambsquaters, pigweeds, smartweed, and velvetleaf).

Liberty (Liberty Link only)—emergence through bloom. Broadspectrum control of many small annual weeds (including marestail) but tends to be weak on many perennials.

Outlook—can be applied post from soybean cracking to 5th trifoliate. It will not control existing weeds but will provide residual activity on annual grasses and small seeded broadleaves.

Pursuit (or Extreme with Glyphosate)—PRE to before bloom and 85 days before harvest (general control of small annual broadleaves and some grasses—good on cocklebur, pigweeds, smartweed, and velvetleaf).

Python—PRE and from 1st to 5th trifoliate (generally will not control emerged weeds, but provide residual control of annual broadleaves).

Raptor—early POST and before bloom (general control of small annual broadleaves and some grasses – good on cocklebur, lambsquaters, pigweeds, and velvetleaf).

Reflex or Flexstar (or Flexstar GT with glyphosate)—PRE to within 45 days of harvest (Prefix also has an early POST label) (general control of small annual broadleaves—good on jimsonweed, pigweeds, ragweeds, smartweed, and velvetleaf).

Warrant—emergence to R2; but label recommends application at V2-V3 state (will not control emerged weeds, but provide residual control of annual grasses and some broadleaves). Warrant Ultra contains fomesafen (Reflex) and is designed to be applied POST (emergence to R2 stage).

Zidua—can be applied post from soybean cracking to 3rd trifoliate. It will not control existing weeds but will provide residual activity on annual grasses and small seeded broadleaves.