There are several insects which damage wheat in eastern Colorado and
western Kansas. Below is a summary of the insects most likely to
You may click below on the insect name to jump to that section, or simply
Bird Cherry-Oat Aphid
Brown Wheat Mite
Cutworms: Army and Pale Western
Russian Wheat Aphid
Bird Cherry-Oat Aphid is relatively
large, a dark green color with a reddish-brown patch toward the rear of
the abdomen. The antennae and cornicles are black. To see a comparison
photo of aphids,
Infestations may occur in fall or spring, and in our area it usually
accompanies warmer-than-noirmal weather. KSU says that populations of 50
or more per tiller at the boot to heading stage may be damaging. The
aphid may roll up the flag leaf into a corkscrew shape that can trap the
awns, resulting in “fish-hooked” heads. This aphid is also a vector of
barley yellow dwarf virus.
Here is summary of the various wheat aphids from KSU in PDF format.
Brown Wheat Mite usually occurs in the spring
in dry, dusty conditions and more commonly near volunteer or in
The mite is very small, with a dark brown, oval body. The first
pair of forelegs are longer than the others. Look for mottled leaves
that appear bronzed at a distance. KSU says that because all
adults are female, and since each can produce 70 eggs in a three-week
period, there is potential for rapidly increasing populations.
Economic thresholds are debated, but several hundred per foot of row
would require treatment, and lower numbers in stressed wheat. Heavy
rains can reduce the BWM populations.
Here is the KSU web page on brown wheat mite.
Cutworms normally infest our wheat in the
spring. Dry years and sandy soils are the most likely to show symptoms,
and south facing hillsides on a warm afternoon are good for scouting.
Scratch the soil carefully, looking for larvae at the 1-2" depth.
The Pale Western Cutworm often causes more damage than the
Army Cutworm, because it clips the plant at the soil level instead
of consuming the leaves. Whitish larvae hatch underground in the spring
from eggs laid by moths in the fall. Control can be more difficult than
the Army Cutworm, because the Pale Western stays below the surface at
The Army Cutworm has a similar life cycle to the Pale
Western, but it feeds above ground during the day. An adult
female may lay 1,000 eggs. Lush wheat with luxuriant growth can
tolerate more worms than a thin stand. Fields slow to green up may
have a cutworm infestation: scout on warm days in sandier portions.
Economic levels can be as low as one cutworm per square foot, or as high
as 4-5 per square foot, depending upon the wheat's stand and vigor.
Comparison photos of the two cutworms
Hessian Fly damages wheat in the
in the fall, and is worse in wet years. KSU says no remedial measures are
available, but some dispute this. Certainly, planting resistant varieties after September 15 and
controlling volunteer are the best solutions.
Using treated seed may help, especially against fall infestations.
Lodging can occur in the spring, especially if a significant fall
Here is the KSU PDF file.
Grasshoppers typically cause problems
in the fall, after wheat drilling. They feed on warm afternoons, then
hide in adjoining cover during the cooler evenings. Bait can be used for
control before wheat emerges. Spraying can be cost-effective: with $4
and 40 bushel per acre wheat, a ten foot-wide loss equates to nearly
$200 per mile of lost yield.
Greenbugs seldom reach economic levels as
far north as our region, although our increasingly mild winters make
them more likely than in the past. They are pale green aphids with a
dark green line down the back.
Click here to see an
Greenbugs usually feed on the undersides of leaves, but their sucking
activity discolors the leaf surface. Small red spots are followed
by leaf yellowing and ultimately leaf death, if left untreated.
Early infestations are spotty, often spreading to cover the field.
Parasitic insects, including wasps and ladybug larvae, can be effective
in reducing greenbug populations. However, chemical control is
often required because parasites arrive too late to prevent damaging
There are resistant wheat varieties which tolerate higher levels of some
greenbug biotypes, but the insect has a history of rapidly evolving into
new biotypes which defeat the resistance traits.
Economic levels are difficult to establish, because plant size, vigor,
and resistance, as well as the levels of parasitism affect the
calculation. Despite this, on very small plants a few greenbugs per
plant may be economic, while ten times that number may be well tolerated
in healthy, larger, resistant varieties.
Russian Wheat Aphids can do
significant damage to wheat in our area. First found in Kansas in 1986,
populations can range from non-existent to severe in any given year.
Untreated fields may have yield losses exceeding 50%.
appearance is similar to greenbugs, with several notable
differences: RWA have a slightly shorter body, with very short cornicles
and antennae. Also, the supracaudal structure on the rear has a
when viewed from the side--twin "tailpipes".
Aphids feed on new growth, injecting the plant with a toxin which
inhibits chlorosis, thereby causing the distinctive whitish and purplish
leaf striping. The leaves are also tightly rolled
around the insect, which makes it harder to find and difficult for
parasitic insects to attack. Severely infested plants take on a
Economic levels are as low as 10 percent of the tillers infested,
especially in smaller plants. After soft dough stage, 30-40
percent of infested tillers is economic. The RWA often appears in spots
which worsen quickly, with the infestation spreading across the field.
Typically, early infestations are mostly wingless, with more winged
insects appearing later in the infestation. Strong southerly spring
winds can bring in large numbers of RWA in a short time frame.
Resistant varieties exist, but as with greenbugs, RWA can evolve into
biotypes that defeat the host plant's resistance.
Here is the KSU RWA download in PDF format.
Another source for wheat insects is the KSU Wheat Insect Guide.
Download it here.
(PDF, 290 Kb)
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For disease information on wheat,
For weed information in wheat,
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Another source for wheat insect information is the KSU 2006 Wheat Insect Guide.
it here. (PDF, 231Kb, 12 pages.)
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