sealPurdue News

May 22, 2002

Weed fields no field of dreams for farmers

WEST LAFAYETTE, Ind. – If you look at many fields around Indiana, you'd swear that farmers had planted a crop of weeds.

While spring rains have kept farmers from planting their fields, weeds – and the problems they create– are multiplying.

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"In some fields the vegetation is so high, farmers will have no choice but to spray for the weeds before they plant," said Tom Bauman, Purdue Extension weed specialist. "Any weeds more than about 18 inches high will have to be sprayed and disked under before planting starts."

Bauman said spraying weeds will delay planting an additional day or two; spraying and disking will hold off planting three to four days.

Larger weeds also will require farmers to increase the rate of application of some herbicide products. He said some products also have longer "burn down" times than others, and farmers should consider using products that dry down weeds in the least amount of time.

Bauman said the window of opportunity also is closing for treating this year's weeds and then rotating to some other crops next year.

"According to the manufacturer's directions, you need to have so many months between herbicide applications," he said. "If farmers are late in applying herbicides this year, there may be carryover injury to the next year's crop."

Crops that cannot be planted within one year of applications of herbicides, such as atrazine, include forages, small grains, such as oats and barley, and vegetables. If applied too late, herbicides specifically designed for soybeans also may damage corn the following year, and vice versa.

For some stubborn weeds, such as Canada thistle, more than one herbicide application may be necessary to control them. Glenn Nice, weed science expert, said contact herbicides only burn down surface parts of a weed.

"Translocating herbicides – those that move through the plant – are required to control the underground root systems," Nice said.

Writer: Beth Forbes, (765) 494-2722;

Sources: Tom Bauman, (765) 494-4625;

Glenn Nice, (765) 496-2121;

Ag Communications: (765) 494-2722; Beth Forbes,;

Related Web site:
Delayed Planting Web site


This west-central Indiana field is covered in Senecio, a weed that many Hoosier farmers will have to deal with before planting can be completed. Purdue experts said weeds this large will have to be burned down and disked under as soon as conditions allow. (Purdue Agricultural Communications Photo by Randy Spears)

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