June 1 quiz – Weeds

Three questions on in-crop herbicide timing…

Grass weeds in LL close

1. Early-season competition from weeds remains one of the biggest threats to canola yield. Research shows that controlling weeds at the one- to 2-leaf stage of the crop can improve yield by ___ bu./ac. compared to waiting until the 3- to 4-leaf stage.
2. Aerial application is an option for some herbicides. This will mean higher costs but could mean higher returns as well if fields need to be sprayed but are too wet for a ground unit. However, 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 ___ metres from non-target plants and animals compared to a 1 metre buffer for ground application.
3. Spraying too late has various risk factors. It reduces yield due to weed competition. Larger weeds are more difficult to control. And the crop itself is also more sensitive. Late glyphosate applications, for example, can cause buds to abort. According to the glyphosate label, what canola leaf stage marks the end of the application window?