Following up on the registration of Fierce in soybeans, Zidua has now been registered for use in soybeans as well. Zidua is sold by BASF and contains the active ingredient pyroxasulfone. Fierce, on the other hand, is a premix of pyroxasulfone and Valor herbicides.   

Pyroxasulfone is a new chemical that was first registered for use in corn last year. It has a similar mode of action to the acetamide herbicides such as Dual, Outlook, and Harness, but is more active at lower rates, provides longer residual control, and has better activity on some broadleaf weeds than the acetamides.  

Zidua can be applied as a preplant, preemergence, or postemergence treatment in soybeans. Preplant and preemergence rates range from 1.5 to 3.5 oz/acre depending on soil type, with lower rates recommended for coarse-textured soils, and higher rates for heavier soils. Postemergence rates range from 1.0 to 3.5 oz/acre, depending on soil type. The maximum use rate on coarse-textured soils is 2.1 oz/acre.   

It is important to understand that Zidua has limited foliar activity and won’t control emerged weeds, so preplant treatments won’t provide any burndown activity. Postemergence applications would be primarily for later-season residual control. Postemergence applications are only allowed between the V1 and V3 leaf stages. Postemergence treatments prior to the V1 stage may result in crop injury.

Zidua has provided good residual control of small-seeded annual grasses and pigweeds.  It can also provide some preemergence control of other broadleaf weeds such as kochia, velvetleaf, and morningglory, but may not be adequate by itself on those species. As with all preemergence herbicides, precipitation is required for herbicide activation. Also keep in mind that the earlier a residual herbicide is applied, the earlier it will start to wear out in the summer. Wheat can be planted 4 months after application of Zidua at 3 oz/acre or less.