There are effective late-fall post-emergence options for management of dandelion and winter annual weeds in wheat for use mostly in those fields that were not treated with burndown herbicides prior to emergence. For late-planted fields where wheat has not emerged, it’s still possible to use the full range of burndown herbicides discussed in a previous article (http://corn.osu.edu/newsletters/2014/2014-32/#5). A couple of questions we received lately about burndown include:
1. Is it possible for pre-emergence applications of glyphosate to reduce the yield of wheat? Not that we know of, as long as the wheat shoot is still underground.
2. What about a burndown of glyphosate plus Sharpen at 2 oz/A? It’s not possible to use 2,4-D as a burndown in fields that have been planted. The combination of glyphosate and Sharpen is an effective alternative to make sure that emerged marestail plants are controlled. The 1 oz/A rate of Sharpen should be adequate this late in the season. The higher rate of Sharpen can improve residual activity, but there is no need for residual this late in fall, and the higher rate won’t persist into spring either.
There are several post-emergence herbicide treatments that can be applied into November. The most cost-effective of these include Huskie or mixtures of dicamba (2 - 4 oz) with Peak, tribenuron (Express, etc.), or a tribenuron/thifensulfuron premix (Harmony Xtra, etc.). Low rates of metribuzin (0.75 - 2 oz of 75DF) can be substituted for the dicamba, but won’t be as effective on several key weeds. Wheat varieties vary in their sensitivity to metribuzin, so consult seed company information before use. We discourage application of 2,4-D to emerged wheat in the fall due to the risk of injury and yield reduction, and most labels do not list this use. Fall application of dicamba has not caused injury or yield loss in our research trials. Consult labels and the “Weed Control Guide for Ohio and Indiana” for information on minimum wheat size/stage at the time of application and other precautions.