Failure to control weeds can spell disaster for your corn crop. However, the timing of weed control is a significant factor in weed control that is often ignored.
The growth of herbicide resistance has led to the need for early weed control. And with farmers planting crops as early as safely possible, this means that weed control needs to occur earlier, as well. Weeds that grow too long in corn are known to hurt yields. In fact, even when all other factors have come together-a well-established stand, proper nutrients, sufficient rainfall-delayed weed control can spell disaster.
Corn plants do things initially that impact yield potential. Early in the season, plants are able to sense from reflected light if there is competition from other plants or weeds. These plants then react accordingly. Since corn grows best with lot of space, early pressure from weeds can lead to potentially high yielding corn to produce lower yields as corn grows taller and spindlier in an effort to beat out other plants and weeds for sunlight. While under-planting corn is a waste of space, overplanting also is discouraged to avoid light reflection from other plants.
The longer you wait to spray weed control, the lower your yields will be as taller weeds encourage smaller corn ear production and fewer kernels because of concern from corn plants over competition. Of course, delayed planting of pre-emergence herbicides isn’t always the fault of the farmer. Excessive rainfall can force farmers to hold back on applying herbicides.
Post-emergence herbicides aren’t always the answer either as rainfall can cause issues for these, as well. For example, rain can delay timely application of post-emergence herbicides which allow weeds to compete for a longer period of time. When an application is finally made, it will likely be less successful. Residual herbicides will then become critical for yield protection.
Controlling weeds at the seedling stage is essential. If these weeds seed, they can produce millions of seeds. Finally, you may want to consider rotating your crops as well as your chemicals in order to control weeds and reduce the chance that herbicide-resistant weeds will evolve. In the end, early weed control is the key to higher yields so you need to devise a strategy to control weeds and have some options should conditions force you to change that strategy.