And how did your waterhemp crop do this year?
As you were guiding your combine through corn and soybean fields this fall, what weeds did you see that concerned you? You probably thought your weed control program should have taken care of those weeds, but for some reason they escaped, and now their seed has gone through the combine and been further dispersed in the field. One of those may well have been waterhemp, which Charles Darwin would have used as his best example of survival of the fittest. The ability of waterhemp to survive herbicides has befuddled some of the nation’s best biochemists in weed control laboratories. Some of us used to control it with a weed hook, and some of your frustrated neighbors have returned to that in patches of waterhemp in fields where herbicides receive no respect. As you are planning your weed control program for next year, what are your strategies for dealing with one of your worst enemies?
Waterhemp is legendary in its ability to re-invent its genetics because it is different from many other weeds. There are male plants and female plants and one male waterhemp plant with a gene that gives herbicide resistant abilities can be spread its pollen to thousands of female plants. Subsequently, a female with herbicide resistance can create over one million seeds for the next crop year.
Purdue agronomists Bill Johnson and Glenn Nice have created a waterhemp fact sheet in which they say waterhemp is an emerging problem in Indiana, but it is a publication that can be distributed in every other Cornbelt state. They say waterhemp has been a significant issue for the past 10-20 years, but is quickly “moving up on the radar of concern.”
Because waterhemp is a cousin to the family of pigweeds—sometimes called amaranth—it resembles many others, and is difficult to specifically identify when it is just emerging in the spring—or year-round for that matter. Johnson and Nice offer these characteristics:
• First true leaves are generally longer than other pigweeds.
• Seedlings are hairless with waxy- or glossy-looking leaves.
• Waterhemp and Palmer amaranth stems are hairless, whereas other pigweeds have hairy stems.
They say waterhemp can be anywhere from four inches to 12 feet tall at maturity, but are usually in the 4-5 foot range when they hit your combine header. They will emerge throughout the growing season, so one trick they play is to emerge just after you apply a contact herbicide. The Purdue weed specialists say a larger percentage of waterhemp will emerge later in the season than other weeds, which is one reason you may not see them when initially scouting the performance of your weed control program.