Manhattan, Kansas
March 26, 2007
Army cutworms have been detected
on some fields of wheat in Kansas as of mid-March, said Jeff
Whitworth, Kansas State University
Research and Extension entomologist.
"At this time, the cutworms are small. By late March, the
cutworms will probably be larger and damage may be more
noticeable," Whitworth said.
Army cutworms oversummer in the Rocky Mountains, he explained.
They fly back to Kansas and surrounding areas in the fall and
lay eggs in the soil. The eggs hatch either in the fall or early
winter.
"Last fall, some early instar larvae were found in Kansas,
indicating that populations this spring could be expected," he
said.
Larvae begin feeding whenever temperatures rise a few degrees
above freezing, Whitworth explained. In wheat, larval damage
first appears as "windowpane" holes. Larvae hide in loose soil
at the base of plants, emerging to feed in the evening. Unlike
some other cutworms, only above-ground plant parts are eaten.
Moisture availability, crop condition, and regrowth potential
are all factors influencing potential losses to the army
cutworm.
"Late-planted fields under dry conditions with poor tillering
may suffer economic damage with as few as one or two larvae per
square foot," Whitworth said. "In most fields, treatment will
not be necessary until populations average four to five worms
per square foot. This applies to any larval stage. Vigorous,
well-tillered fields under optimal growing conditions can
tolerate even higher populations - as many as nine or 10 larvae
per square foot without measurable yield loss."
Labeled treatment options for army cutworms on wheat include
beta- cyfluthrin (e.g. Baythroid XL, and others),
lambda-cyhalothrin (e.g.
Warrior with Zeon Technology, and others), gamma-cyhalothrin
(Proaxis), and zeta-cypermethrin (Mustang MAX).
There have also been reports of army cutworm infestations on
canola this spring in Kansas. Canola fields are quite
susceptible to army cutworm damage in the early spring, said
Mike Stamm, canola breeder for K-State and Oklahoma State
University.
Canola should be treated when there is an average of two or more
larvae per foot of row, said Phil Sloderbeck, K-State Southwest
Area Extension entomologist. It is important to scout canola
fields for these insects.
"Army cutworms find canola very palatable, and four to five per
square foot can cause severe damage to stands," he said. "Stands
can be completely lost if left untreated. Look for foliar tissue
damage and severed green leaves lying on the ground as evidence
of feeding.
Damage may initially be more visible in areas of the field where
stands are thin."
Labeled treatment options for army cutworms on canola include
bifenthin (e.g. Capture, and others), lambda-cyhalothrin (e.g.
Warrior with Zeon Technology, and others), and gamma-cyhalothrin
(Proaxis).
When making an insecticide application for army cutworms,
growers should be sure that temperatures will be above 50
degrees for three to four days after the application is made,
Whitworth said. Always read and follow label directions.
Alfalfa may also be affected by army cutworms, he added.
"First-year fall-planted fields are the most susceptible,"
Whitworth said. "However, foliage feeding in established stands
may reduce yields, especially in the first cutting. Treat
first-year fields when there is an average of two or more larvae
per square foot.
Established stands should be treated when there is an average of
four or more larvae per square foot."
Most of the same insecticides listed for wheat and canola are
registered for alfalfa also. The scientists said, however, that
producers should always read and follow label directions and
consult the K-State Extension Insect Management Guides for the
crop of concern.
More information on treating wheat for army cutworms is
available at county and district K-State Research and Extension
offices and on Extension´s Web site at:
http://www.oznet.ksu.edu/library/ENTML2/MF745.pdf.
More information on treating canola for army cutworms is
available at
http://www.entomology.ksu.edu/DesktopDefault.aspx?tabid=646
and information on treating alfalfa for army cutworms is
available at
http://www.oznet.ksu.edu/library/ENTML2/MF809.pdf.
K-State Research and Extension is a short name for the Kansas
State University Agricultural Experiment Station and Cooperative
Extension Service, a program designed to generate and distribute
useful knowledge for the well being of Kansans. Supported by
county, state, federal and private funds, the program has county
Extension offices, experiment fields, area Extension offices and
regional research centers statewide. Its headquarters is on the
K-State campus in Manhattan. |
|
