Friday, July 18, 2014

Low Levels of Insects Popping Up in Crop Fields

Contact: Jill Scheidt, agronomy specialist
Headquartered in Barton County
PHONE: 417-682-3579

LAMAR, Mo. -- Jill Scheidt, agronomy specialist with University of Missouri Extension in Barton County, scouted fields northeast of Lamar near Hwy. A and Hwy. EE on July 16.

Scheidt offers this advice from the field.


Corn is in the milk stage and corn earworms were seen feeding on kernels. “In one field I was finding one earworm in 5 out of 10 stalks, but in the majority of fields, one or no earworms every 10 stalks,” said Scheidt.

According to Wayne Bailey, state entomologist with University of Missouri Extension, there is no recommended threshold level; insecticide treatments are not economical because multiple applications are needed to obtain effective control.

“Corn earworms cause less than one percent yield loss because they feed on the tip, where the kernels don’t always fill,” said Bailey. Bailey suggests the following best management practices: early planting, selecting BT varieties with corn earworm resistance and varieties with tight husks.

According to Laura Sweets, state pathologist with University of Missouri Extension, fungicides are most profitable when disease, or weather conditions favoring disease, and disease susceptible varieties are present. “The optimum time to apply fungicides is from tasseling to the blister stage in corn,” said Sweets.


Soybeans were in the first trifoliate to bloom stage. “I saw bean leaf beetle, blister beetle, grasshopper and Japanese beetles feeding but not at threshold levels,” said Scheidt.

Threshold levels for all foliage feeding insects are: 30 percent defoliation before bloom and 20 percent defoliation during and after bloom.

“Defoliation refers to the whole plant, so the whole plant must have 20 or 30 percent defoliation,” explains 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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