Thursday, April 10, 2014

Consider the Economics First Before Spraying Fields for Aphids or Weeds

Contact: Jill Scheidt, agronomy specialist
Headquartered at Barton County Extension Center
Tel: (417) 682-3579

LAMAR, Mo. – When aphids and weeds start showing up in area wheat and corn fields, farmers need to consider the cost of herbicides before application according to Jill Scheidt, agronomy specialist with University of Missouri Extension.

“I scouted fields on April 9 around Golden City and see any aphids yet but temperatures were still cool,” said Scheidt. “If temperatures are below 60 degrees, aphids are not active. If aphids are not present in wheat fields and if temperatures are below 60 degrees, an insecticide is not economical to apply.”

Kevin Bradley, a state weed specialist with University of Missouri Extension, recommends a two-pass herbicide program when spraying corn.

“Over the past 11 years, in 67 percent of corn trials, the highest yield was obtained by using a pre-emergent, followed by a post-emergent herbicide application; regardless of whether you plant conventional or not,” said Bradley.

The economic threshold level of weeds depends on species and growth stage of the weed.

To estimate weed density in wheat, count the number of plants in a square foot in 5 to 10 random places in the field. If weeds make up more than 30 percent of the plant population in that square foot, treatment is justified.

“If weeds make up 5 to 29 percent of the plant population, wheat prices and herbicide costs should be considered first,” said Scheidt.

The weekly field scouting report is sponsored by University of Missouri Extension and Barton County Extension. For more information on this scouting report, or to learn how to receive it a week earlier by telephone, contact the MU Extension Center in Barton County, (417) 682-3579.


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