Marestail control in wheat and some other weed stuff
There are several methods for management of marestail in wheat, and following any of these will take care of most winter annual weeds as well. Keep in mind that where wheat will be planted following soybeans, the large marestail that may be present in soybeans are not a concern since they are finshing their life cycle anyway. The plants of concern are the seedlings that emerge in late summer into fall, which can overwinter. A few options to consider follow. This is not an all-inclusive list of herbicide options, but some that make the most sense to us. It’s possible that some of the newer broadleaf products for wheat also have a fit, although none have residual activity.
- Tillage. Does not guarantee the complete absence of marestail but usually takes care of the problem for the season. Tillage should thoroughly and uniformly mix the upper few inches of soil to uproot existing plants and bury any new seed. Scout in spring to make sure control is adequate.
- Preemergence burndown + residual. The combination of glyphosate + Sharpen + MSO will control existing marestail and also provide residual control into fall. We suggest Sharpen rates of 1.5 to 2 oz/A. Spray volume of 15 to 20 gpa is required.
- Late fall POST. We have generally applied these in early November, and wheat should have 1 to 2 leaves depending upon the product. Options include Huskie, and combinations of dicamba (4 oz) with tribenuron (Express) or similar product. Do not apply products or mixes containing 2,4-D POST to wheat in fall.
- Spring POST. In our research, spring herbicide plus the competition from an adequate wheat stand has been effective, even though 2,4-D can be weak on overwintered marestail plants. Options include Huskie, 2,4-D, 2,4-D + dicamba, or combinations of 2,4-D with an ALS-inhibiting products, such as thifensulfuron/tribenuron (Harmony Xtra etc). The rate of dicamba that can be used in spring is too low to control marestail on its own. Most marestail populations are ALS-resistant, so in the ALS mixtures indicated above, the partner herbicide is carrying the load for marestail control.
Fall is also a good time to work on poison hemlock infestations. Hemlock is a biennial (2-year life cycle). The large plants that become evident in spring were actually present in a low-growing form the previous fall, when they are in their first year of growth. Control of this weed is often ignored until late spring when it is large and fairly difficult to control, but it is much more easily controlled in late fall. In areas, fencelines, etc where poison hemlock is known to occur annually, consider a late fall application of 2,4-D + dicamba, glyphosate + 2,4-D, etc.
Finally, some reminders on burcucumber control as herbicide programs for next year get planned this fall and winter. Palmer amaranth notwithstanding, burcucumber remains among the most difficult weeds to control. A number of preemergence and postemergence herbicides have substantial activity on it, but its ability to emerge in great numbers in mid-season allows it to escape even effective programs. It’s worth reviewing the burcucumber information in the “Problem Weeds” section of the “Weed Control Guide for Ohio, Indiana, and Illinois”. We have historically had more questions about control in corn, possibly because it can emerge in tall corn that is difficult to get through with a sprayer. A combination of preemergence and postemergence applications is certainly necessary in both corn and soybeans. POST options in soybeans include Classic, glyphosate, and glufosinate – multiple POST applications are most effective. We conducted a two-year study on control in corn, and found that inclusion of mesotrione (Callisto etc) in the POST application offered the most hope for limiting late-season emergence, although we still observed emergence in July where this was used. Mesotrione has both foliar and residual activity on burcucumber, whereas all other POST herbicides lack residual activity. Most effective residual control following planting occurs with products that contain isoxaflutole (Balance, Corvus) or mesotrione (Lexar, Acuron, Resicore, etc), which should be supplemented by the addition of atrazine.