If weeds and crop are advancing toward the end of the application window and the ground is too soft and wet to support a sprayer, then aerial spraying may be the best economic response. Here are the options for aerial herbicide application in canola:
—Roundup WeatherMax is the only glyphosate registered for aerial application at this crop stage, but use is subject to certain conditions which are outlined in detail on the label. (Many others are registered for pre-harvest.)
—Liberty (glufosinate) is registered for aerial application at this stage. Remember, Liberty works best at higher water volumes. Centurion and Select are also registered for aerial application.
—None of the Clearfield herbicide system products is registered for aerial application on Clearfield canola. —Assure II, Equinox and Poast have aerial labels.
Benefits of aerial application: If weeds are plentiful, at the same stage or ahead of the crop, and canola canopy closure is unlikely to effectively limit their growth, then it will probably pay to control these weeds by air if you have no other option. Aerial spraying also avoids wear and tear on sprayers and on the field when conditions are wet. Under these very wet conditions, ground sprayers can leave deeps ruts to contend with in subsequent spray applications and at harvest, while destroying the crop in those tracks. And getting a sprayer unstuck can be a long, messy job.
Downsides to aerial application: Buffer zone requirements for aerial application are substantially further from sensitive habitats than buffers for ground application. For Liberty, for example, the buffer zone for aerial application is 30 metres from non-target plants and animals compared to a 1 metre buffer for ground application. Aerial application also represents another cost. On that note, in very wet conditions, growers should make sure the crop has recovered before stacking on the extra expense of aerial weed control.