Friday, May 30, 2014

Scout for Armyworms Now Says Extension Specialist

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

LAMAR, Mo. -- Jill Scheidt, agronomy specialist with University of Missouri Extension, saw threshold levels of armyworms when scouting in fescue and wheat field on May 28 around Golden City, Arcola and Iantha.

Threshold levels are four armyworms per square foot or when two percent of heads are clipped.

Scheidt recommends treating fields at threshold immediately as armyworms can clip heads in the entire field in one night.

“Beat fescue or wheat together, and then look on the ground for armyworms,” said Scheidt.

Armyworms are identified by light and dark stripes running the length of the body and four pro-legs at the center of the body. Armyworms commonly feed during the morning and night hours when it is the coolest.

Armyworm life cycles last 30-45 days and mature larvae are 1.5 inches long.

According to Wayne Bailey, state entomologist with MU Extension, armyworms go through five to seven instars and usually take two to three days per instar. If armyworms are one inch long, there is about one week of feeding left.

Armyworms do most of feeding in later stages of life.

A rate of 1.8- 4.0 oz/ acre of Mustang Max is recommended to treat armyworms in wheat and fescue and contains a 14 day harvest and forage interval for wheat and 0 day interval for fescue.

“Before treating, inspect the larvae for the presence of small white egg-shaped structures, usually behind the head. These are eggs of a parasitic fly and indicate the parasitized larvae will soon stop feeding and eventually die,” said Scheidt.

In the corn fields that she scouted, Scheidt said she found corn in the 9-10 leaf stage. No diseases were seen, but corn leaves showed evident of a small amount of corn borer feeding. However, Scheidt says this rarely justifies treatment.


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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