Manage Burcucumber with Corn Silage Harvest

As some prepare for corn silage harvest, managing burcucumber should be a top priority. Burcucumber can germinate and emerge late into the season, especially under moist conditions. And it is not until it gets above the crop canopy that it is often noticed. Thus, we are starting to get more inquiries about how to control burcucumber that has canopied over-the-top of corn. Penn State research shows that ensiling green burcucumber seed is an effective technique for killing viable seed, but that ensiling does not affect mature seed. Effect of an 8-week ensiling period on burcucumber seed revealed that if the burcucumber seeds were immature (green or cream-tan colored; see image below) only 2% remained viable, as compared to mature seed (dark brown seed coats), that were 87% viable. This suggests that early harvesting of a crop as silage may prevent viable seed production in burcucumber-infested fields. Silage harvest also prevents mature seed from reentering the field through the combine.

Immature burcucumber seed that would be destroyed by ensiling. (Credit: Penn State Weed Science, D. Lingenfelter)

If burcucumber cannot be removed with corn silage harvest, there are no labeled and effective herbicide options that can be applied to tasseled corn. Products like glyphosate are not allowed until the grain is mature and many of the other herbicides like Peak, dicamba, Callisto, Liberty, and others stipulate that they must be applied prior to V8 corn stage or earlier. So don't be tempted to use a drone or high-clearance sprayer to apply products at this time of year for burcucumber control. The next opportunity for certain herbicides to be legally applied to corn would be as a harvest aid (or weed desiccant) just prior to grain harvest. Once that time gets closer, we will provide more details on what herbicide options are available for that type of application.