Odds of 95% usually sound like a close-to-sure bet, but when it comes to weed control for waterhemp in corn fields, the “house” will very likely win.

Belchim USA’s national technical service and development manager, Dennis Long, explains it this way:

“If your post-emergence weed control product provides 95% control, but 50 waterhemp seedlings per acre escape, you can be in real trouble.”

Long does the math estimating one waterhemp plant can produce about 400,000 seeds when competing with a corn crop.

“Those 50 escape plants multiplied by 400,000 seeds equals 20 million seeds per acre – or 460 seeds per square foot,” he says. “Tillage can bury many of those seeds deeper than they can germinate the following season, even if they are plowed 6 inches deep.

"Research, however, shows even at 6 inches 20% of the buried seeds remain viable after 1 year. After 2 years, 10% remain viable, and after 3 years, 5% (23 seeds per square feet) still present a competitive threat to a cash crop.” 

Long says 23 plants may not seem like many, but studies have shown just 8 waterhemp plants per 11 square feet can reduce corn yield by 74%. Escapes — treated plants that survive — are also associated with increased rates of herbicide resistance development.

“When planning your weed control program, it’s very important to sharpen your control further even if your post application will kill 95% of seedling waterhemp,” he adds.

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