In most situations, weeds that emerge during late June or July will have little impact on crop production, although many of these weeds will become visible later in the season, especially in soybean. Growers also need to consider whether the weeds can be effectively controlled and the impact of the herbicide treatment on crop yields. At this time of year, weeds usually don't get noticed until they become fairly large. The combination of large weeds and high temperatures will reduce the effectiveness of most herbicide treatments. In addition, postemergence herbicides are more likely to cause significant yield losses when applied to crops in the reproductive stage.
Many herbicides prohibit application to crops in reproductive stages of growth.
In summary, late-emerging weeds may be appearing in fields across the state. This information subject to a usage policy .