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New wheat herbicide needed, registration delayed

For the past two years we have been evaluating pyroxasulfone (Zidua) in wheat. This product is manufactured by Kumiai Corporation. Pyroxasulfone is currently set to be marketed by several different companies for use in corn, soybeans, wheat and other crops once it receives full registration.

FMC will have a product named Anthem (pyroxasulfone + Cadet) and Valent will have a product called Fierce (pyroxasulfone + Valor) — both good pigweed herbicides in soybeans. Under the current scenario, BASF will market the only standalone pyroxasulfone product, Zidua.

In addition to corn and soybeans, Zidua will have a label for use in wheat. This is good news in Arkansas and other wheat-growing areas across the Mid-South. For the past several years we have seen a dramatic increase in populations of ryegrass that are cross resistant to at least two, if not three, wheat herbicide modes of action.

In a recent ryegrass survey conducted in Arkansas, we found that just about every ryegrass population tested was resistant enough to the herbicide Hoelon to make it virtually useless to us. This was expected. Of more concern, over half the samples tested were also resistant to the ALS chemistry like Finesse, Osprey and Powerflex.

The newest product that we have for ryegrass control in wheat is Axial XL. Chemically speaking it is a cousin to Hoelon, but they are different enough that so far Axial has effectively killed most Hoelon-resistant populations. In our survey, around 22 out of 300 populations sampled had some resistance to Axial.

Once registered, Zidua will represent a brand new mode of action in wheat herbicides. As you can see from above, this will be needed. In our research, Zidua has provided excellent control of resistant ryegrass in wheat. It controls most grasses and small-seeded broadleaves.

Zidua is in the same group of chemistry as Dual herbicide, although it is not a true chloroacetamid. It is effective at rates ranging from 1 to 3 ounces per acre. I am not sure what the labeled rate for wheat will be. Zidua will need to be applied prior to the ryegrass emerging, usually as a true pre-emerge treatment.

For those of you planning to grow wheat this fall, our best resistant ryegrass program is to apply Axiom plus Prowl H2O in the fall, just after wheat emerges (1-leaf to 2-leaf), and follow this with Axial XL in early spring. This assumes that you have both Hoelon and ALS resistance.


My wheat research program is supported by the Arkansas Wheat Promotion Board and numerous industry grants, we appreciate this support. See the wheat section of the MP44 online at for more information.

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