Wheat Weed Control
Dr. Anthony Ohmes, Extension Agronomist, Charleston, MO
The bad news: weeds continue to be a problem in winter wheat. The
good news: we have a new herbicide and have some other herbicides
on the way.
Ryegrass continues to be among our most difficult problems. We
currently have four herbicides which control ryegrass: Hoelon,
Achieve, Finesse and Osprey. Hoelon and Achieve are grass-only
herbicides, and in some cases, ryegrass has become resistant to
these grass-only herbicides. Osprey is a new herbicide from Bayer.
Osprey controls ryegrass as well as many common broadleaf weeds.
Finesse controls ryegrass and broadleaf weeds, but requires growers
to plant an "STS" soybean variety.
The main twist to all of these herbicides is that they should
ideally be applied in the fall. Unfortunately, many wheat growers
tend to plant and then forget about weed control until "Harmony
time" in late February. February is often too late to control
ryegrass, even though Osprey has showed promise.
Bayer is also developing the corn herbicide Axiom for winter wheat.
Axiom contains both Sencor and Define (Define is a preemergence
grass herbicide, and is cousin-chemistry to herbicides like Lasso
and Dual). Sencor is already a commonly-used wheat herbicide;
however the Define appears to improve the amount of ryegrass
control. Beyond in Clearfield wheat has also done a good job of
controlling ryegrass; however, the availability of Clearfield wheat
lines is still unclear.
Resistance management in ryegrass will be important: 1) We already
have some ACC-ase (Hoelon and Achieve) resistance and 2) ALS
herbicides (the mode of action for Osprey and Finesse) are somewhat
resistance prone. It is important to rotate modes of action
whenever possible.
Another common problem is cheat- with Sencor being the primary
cheat-controlling herbicide. Cheat control is difficult on a sandy
soil: Last fall, when our Sencor rate was high enough to control
cheat, we caused severe wheat injury. Monsanto has a cheat
herbicide named Maverick that is used more in the Western US. Some
growers have used Maverick, however, this herbicide requires that
STS beans be planted after wheat harvest.
Cornflower or bachelor button is another common sandy-soil weed
problem. Our best cornflower control has come from 2,4-D or
Buctril; however, Osprey appears to do an acceptable job on moderate
infestations.
2004 Field Day Report
