Louisiana: Weed Management Programs in Winter Wheat

Uncontrolled blue mustard in a thin stand of winter wheat. Photo: Robert Klein, UN-L

Uncontrolled blue mustard in a thin stand of winter wheat. Photo: Robert Klein, UN-L

Weed management in wheat is not extremely complicated, but subtle changes in the weed spectrum can really cause significant issues.There are not many herbicides labeled for use in wheat and only a few provide control of grassy and broadleaf weeds.Others are specific for grassy or broadleaf weeds.

For example, Finesse, metribuzin, and Powerflex HL will control both most grassy and broadleaf weeds.Sharpen, Anthem Flex, Zidua, 2,4-D, dicamba, Osprey, Harmony Extra, and Axial XL are usually for either grassy weeds or broadleaf, although Anthem Flex, Zidua, and Osprey do provide control of broadleaf weeds.

Metribuzin has a major caveat that must be understood before applying it.Some wheat varieties are susceptible and some are tolerant to metribuzin.The LSU AgCenter, Mississippi State University, University of Arkansas, and University of Kentucky (probably others) have evaluated wheat tolerance to metribuzin in the past, so I suggest searching on the internet for this information or ask the person you purchased the seed from.That said, a postemergence application metribuzin in the fall provides excellent control of small grass and broadleaf weeds in wheat.

Another issue is ALS-inhibiting herbicide- and/or clethodim-resistant Italian ryegrass.In wheat, ALS-inhibiting herbicides that will control susceptible Italian ryegrass are Finesse, PowerFlex HL, and Osprey, so if resistance is present, then these herbicides may not be a good choice.Clethodim is utilized on many acres in Louisiana for glyphosate-resistant Italian ryegrass control in the spring at burndown.Unfortunately, many producers are reporting poor control with clethodim and the LSU AgCenter is investigating the possible presence of clethodim-resistant Italian ryegrass.Clethodim is an ACCase-inhibiting herbicide.

In wheat, Axial XL is also an ACCase-inhibiting herbicide and is a great choice for Italian ryegrass control.Now, if clethodim didn’t control the Italian ryegrass previously, does that mean Axial XL won’t work either?I cannot say for sure, but I wouldn’t bet on it.So, Axial XL may not be a good option for Italian ryegrass control too.

In addition, if Finesse is applied preplant, preemergence, or postemergence, the rotation interval to cotton or soybean is 18 months.However, the interval is only 4 months for BOLT soybean and 6 months for STS soybean, so if Finesse is applied, the grower is locked into a BOLT or STS soybean variety.This issue is the primary reason I usually do not often suggest the use of Finesse.


Source URL: https://www.lsuagcenter.com/profiles/lblack/articles/page1603474466743