Lousy germinators still overwhelm crops

Only 1% of some weed seeds will germinate in the year they’re produced. Compare that to 95% for corn and soybeans. So why is weed control still such a big issue?

Bill Johnson, Purdue weed control specialist, says the real difference is that weeds play the numbers game. Weed dynamics work against the crop. Consider pigweed, for example. It’s a small-seeded broadleaf weed. “One plant grown without competition can produce a million seeds,” Johnson says.

Key Points

Weeds compete through sheer, overwhelming numbers.

Germination percentages for weeds are extremely low.

Stop weeds by preventing them from going to seed.

An acre of pigweeds can produce 2 billion seeds. So if only 1% germinate in any given year, that’s still a lot of pigweed plants! “If only 1% germinate, you’ve still got 20 million pigweed seedlings the next year. Compare that to 30,000 corn plants and 150,000 soybean plants. The odds are definitely stacked,” says Tom Jordan, another Purdue weed control specialist.

Part of the take-home-message is that weeds can simply overwhelm a crop with seed numbers. So it’s important not to have many plants going to seed.

Once seeds are in the soil, they can last for several years, depending upon the species. However, Jordan says the ability to survive 30 to 40 years in the soil and still germinate is exaggerated for some species.

Burcucumber: the nightmare weed

What can come up in July, or even perhaps by the first of August, and still produce a powerful, 35- to 40-foot vine by harvest? It’s burcucumber.

One thing that makes it tough to control is its ability to emerge through multiple flushes during the season, notes Tom Bauman, Purdue weed control specialist.

Up until this year, options were 2,4-D, which isn’t particularly effective against it, or Banvel, in corn, which works OK until a new flush arrives. Neither of these products have residual control.

A new product on the market, Peak from Syngenta, is available this year.

“Glyphosate will work, but only if the vines are up,” Bauman explains.


Weeds win! Or so it appeared at this point. A huge number of plants germinating from seed choke this field. It was later cleared up with herbicide, but it was a lucky kill, weed specialists say.

This article published in the June, 2011 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.