(1999 Data)
Northwest:
Big Horn, Fremont, Hot Springs, Park Washakie
Northeast:
Campbell, Crook, Johnson, Sheridan, Weston
West:
Lincoln
South Central:
Natrona, Sweetwater
Southeast:
Converse, Goshen, Laramie, Niobrara, Platte
Description of Crop:
Oats are an annual grain crop used for seed production, livestock feed,
breakfast cereals, oatmeal, flour and cosmetics, and as a cover crop for
alfalfa.
Cropping System:
Oats grow best in the cooler regions of Wyoming, but can be grown in
warmer areas if irrigation is available. It is a spring seeded crop, and
should be planted as early as possible. In southeastern Wyoming, oats should
be planted by March 1, northeastern Wyoming planting should be by March
15, and oats should be planted after April 1 in the San Luis Valley. The
optimal soil temperature for planting is 40 F. Seeds should be placed 1
- 2" into the soil. Some growers use 6" row widths, while others use 10
- 14" row widths.
Conventional tillage is used. Oats are mostly furrow irrigated, but some pivot irrigation and dryland production does occur.
Oats that are being planted as a cover crop for alfalfa are planted at 20 - 30 lbs. of seed per acre, whereas oats for grain production are planted at a density of 100,000 plants per acre.
The fertilizer requirement for oats is one pound of nitrogen per bushel of grain. Fertilizer is usually applied pre plant or prior to boot stage.Manure is also used. Too much nitrogen can cause severe lodging.
Oat hay is harvested in late June. Oat grains are harvested in late July to August. When the grain crop is harvested, it is usually swathed first, then combined. However, if the crop is free of weeds, the standing crop can be directly combined.
Store oat hay at 13% moisture.
Critical Pest Management Issues:
Weed control is an important consideration when planting oats. Winter
annuals can be a problem, but can be eliminated by planting at the proper
time, with proper management and pre-plant weed control. Weed problems
are also dependent upon the field's weed history. Using oats as a cover
crop for alfalfa limits herbicide use.
Oats are sensitive to injury from herbicides. Herbicide application must be early when weeds are small and oats are in the 5-leaf stage. Late summer or early fall herbicide application on stubble is an effective control of annual or perennial weeds after harvest.
Insect and disease problems are not as prevalent as weed problems. Aphids transmit many disease problems. Fungicides are primarily used for seed treatment.
Cultural Controls:
Accurate timing and application of irrigation water, in addition to
accurately timed planting will reduce pest pressures on the oat crop.
Bird cherry oat aphids are olive-green in color with a reddish-orange
area on their rear end. They are medium sized, 0.05 - 0.10", with long
antennae, long dark tube-shaped cornicles, and dark colored legs. The aphids
feed on oats by sucking plant juices. Bird cherry oat aphids vector barley
yellow dwarf virus.
Russian Wheat Aphid
Diuraphis noxia is one of the most destructive species in Wyoming. The Russian wheat aphid (RWA) damages small grains by injecting saliva into and sucking sap from plants. Yield losses of 50% or more from this pest can be expected if economic infestations are left untreated. RWA are yellow-green or gray-green in color and are often covered with wax. RWA are small, less than 0.0897" in length, and are convex and elongate. Two forms of RWA are found in Wyoming during the year: a wingless female and a winged female. In Wyoming, most severe spring infestations are caused by wingless aphids. Winged aphids begin to appear in Wyoming in April and May and flights peak during July. At this time winged aphids include both local aphids and immigrants from the south. Winged aphids infest spring grains. Grasses serve as alternate hosts for RWA during the period between grain harvest. Weather conditions that favor cool season grasses and volunteers will increase the number of aphid infestations. Aphid feeding prevents young leaves from unrolling. RWA colonies are found within the tubes formed by these tightly curled leaves. This not only makes it difficult to achieve good insecticide coverage, but also interferes with the ability of predaceous and parasitic insects to reach and attack aphids. Leaves infested by RWA have long white, purple or yellowish streaks. Heavily infested plants are stunted and some may appear prostrate or flattened.
Army Cutworm
Euxoa auxiliaris have a wide host range and feed on most crops
grown in Wyoming. Adult moths are brown with light brown or black markings
on the forewings and have a wingspan of about 2". The larvae vary in color
from dull green to brown with faint stripes on the back and a brown head.
The army cutworm has one generation per year, and eggs hatch in the fall
following sufficient moisture. The army cutworm larvae spend the winter
as partially grown caterpillars. They feed on warmer days throughout the
winter and feed more frequently in the spring as they mature. Army cutworm
caterpillars are climbing cutworms that always feed above ground during
the night and/or on cloudy days. They are found under soil clods and other
debris during the day. After development is complete, they build a small
pupation chamber several inches below the soil surface. Moths emerge in
May and June and migrate to higher elevations in the Rocky Mountains to
escape high summertime temperatures. In late summer and early fall, the
moths return to the plains to lay their eggs. With adequate moisture, eggs
hatch and larvae of the next generation start feeding as weather conditions
permit. Their feeding has the most effect on yield when there is relatively
little foliage for them to feed on, which increases the likelihood of damage
to the crown.
Armyworm
In Wyoming, the armyworm is mainly a pest of spring grains. The armyworm
occurs in eastern Wyoming and in the San Luis Valley. Mature larvae are
about 1.5" in length, smooth-bodies, and dark gray to greenish-black in
color. They are characterized by five stripes, three on the back and two
on the sides, running the length of the body. While the stripes on the
back vary in color, the stripes on the sides are pale orange with a white
outline. The head capsule is remarkable for its "honeycomb" of black markings.
The armyworm is unable to survive Wyoming winters. Instead, armyworm moths
migrate into Wyoming in early summer. They lay their eggs in rows or clusters
on the lower leaves of various grass crops. Dense grassy vegetation is
preferred for oviposition. Newly hatched larvae move with a looping (inchworm)
action. Larvae feed at night and on cloudy days, and hide under crop debris
during sunny periods. Armyworms feed on leaves, kernels, and beards of
heads
of small grains. Their most obvious damage to small grains is by clipping
the heads, causing them to fall. One or more generation may occur per year.
Banks Green Mite
Heavy populations of Banks green mite can kill small plants and reduce
kernel size in larger plants. Banks green mite produces heavy webbing to
protect colonies consisting of eggs, immatures and adults. Damaging leaves
first become yellow and then brown and necrotic. The overwintering form
of the mite is bright orange in color. With the onset of winter conditions,
the mites move to the crowns of the plants where they feed until spring.
In the spring small pearly white eggs are laid which eventually give rise
to pale to bright green male and female adults.
Brown Wheat Mite
Brown wheat mites spend the summer in the soil as a white egg resisting
hot, dry conditions. In the fall, as temperature and moisture conditions
improve, these eggs start to develop and hatch after 10 days incubation.
Females follow in about two weeks. These females lay round, red eggs which
give rise to further fall (1 or 2) and spring (2 or 3) generations. As
summer conditions return, a generation of females is produced which lay
only the white over summering egg. Both egg types are placed on soil particles
near the base of the plant. Brown wheat mites feed during the day and spend
the night in the soil. Their activity peaks at about mid-afternoon on warm,
calm day. This mite is not affected by cold temperatures, but populations
are quickly reduced by driving rains of 0.33" or more.
English Grain Aphid
The English grain aphid is a yellow-green to reddish brown, medium sized
aphid with antennae greater than half the body length. The cornicles are
medium sized and black. Antennae and leg joints are dark colored. These
aphids overwinter mainly in the mature and nymph stages, but a few individuals
may overwinter in the egg stage. Only females overwinter, and with the
warm spring temperatures they begin giving birth to live young. Males appear
during the fall and mate with true females. English grain aphid colonies
often develop on leaves and then move to heads in the boot stage. The aphid
is a vector of barley yellow dwarf virus.
Grasshoppers
Grasshoppers follow a roughly 22-year cycle in Wyoming, with the last
major outbreak occurring in the late 1970s and early 1980s. Grasshoppers
vary considerably depending on the species. Grasshopper nymphs have a similar
appearance to adults but are smaller in size. Grasshopper eggs are laid
in undisturbed areas, usually in late summer and early fall. Small nymphs
or "hoppers" hatch the following spring. Winged adults will appear 5 -6
weeks after hatch. A few Wyoming grasshopper species have eggs that hatch
in late summer and overwinter as nymphs. The usual pattern of grasshopper
damage in field crops is for early development to occur in weedy areas
of roadsides, fence rows, irrigation ditches, and other non-crop areas.
As these food plants are eaten or dry down, the grasshoppers leave in search
of other food, often an irrigated crop. Here they will first feed in the
field margins and then, conditions permitting, spread throughout the field.
Most field crop damage is caused by the differential, redlegged, two-striped
and migratory grasshoppers.
Greenbugs
Greenbugs are light green aphids with adults having a darker green stripe
down the back. Adults may be winged or wingless. All wingless greenbugs
are female and they give birth to females. During the summer, females start
to reproduce within a week and may produce as many as 80 female offspring
during their 25-day adult life span. The legs of greenbugs are green but
their feet are black. The cornicles (small pipes near the rear end) are
green with black tips. Generally, greenbugs are found in colonies on the
underside of the lower leaves. Sometimes they may also be found in the
whorl of the plant until the head emerges. Greenbugs migrate north from
Texas and Oklahoma on weather fronts. This migration generally occurs in
late May or early June but usually does not reach economic levels until
late June or July. In the process of feeding, greenbugs inject toxins into
the plant, which apparently break down cell walls to facilitate feeding.
The toxins cause a red discoloring of the leaves, which in conjunction
with removal of the cell contents, will cause the death of the leaf if
enough greenbugs are feeding. During the digestive process, greenbugs disperse
a sticky, shiny material called honeydew from the cornicles. Honeydew may
interfere with the transpiration process of the plant.
Management:
Insecticides:
Pre- and post-emergence damping-off and seedling blights occur with
all crops. Soil-inhabiting fungi (Fusarium spp., Penicillium
spp. Pythium spp., and Rhizoctonia solani) cause these diseases.
They are characterized by missing or collapsed plants. When pre-emergence
damping-off occurs, seedlings fail to break the soil surface. The germinating
seed is rotted while still in the ground. With post-emergence damping-off,
seedlings still in the cotyledon stage will rot at the soil line. The stem
appears pinched and plants fall over. Seedling blights occur after true
leaves emerge. The developing root system rots and plants collapse. Seedling
diseases are problems when soils are cold and wet immediately following
planting. These conditions can delay germination or stress developing seedlings,
which allows pathogens to attack. Crusting caused by poor soil preparation,
hard rain, or excessive trash on the surface also contributes to disease.
Fungicide seed treatment combined with avoiding cold wet soils and good
soil preparation will best manage these diseases. These diseases are favored
by cool, wet, poorly drained soils.
Covered Smut
Ustilago segetum is a fungus carried on seed. The symptoms include
blackish masses of smut spores replacing kernels. The smut mass tends to
remain enclosed by a whitish membrane until broken by harvesting. Chaff
is not completely destroyed as it is with loose smut of oats.
Crown Rust and Stem Rust
Rusts are caused by Puccinia in small grains. They are characterized
by light orange-brown pustules that occur on leaves and stems. Many but
not all rust pathogens require alternate hosts. One or both of these may
be of economic importance. Rusts overwinter in debris, volunteers and alternate
hosts or are blown up from the south each year.
Helminthosporuim Leaf Blight
On oats, lesions on leaves are small initially, enlarging to long stripes
of dead tissue. Sometimes distinct spots do not form but leaves wither
as if by drought. It is usually associated with cool weather.
Bacterial Leaf Blight
Pseudomonas glycinea occurs in poorly drained wet areas. The
bacterium is easily spread in the field by tillage equipment, surface water,
and animal life in the soil. Bacterial leaf blight usually only occurs
on the upper leaves. Small water soaked lesions form that eventually coalesce
to larger lesions that may cover entire leaf. These spots can advance rapidly
and cause blight and generally are found associated with sprinkler irrigation
in cool wet weather. The bacteria overwinter on and in seed and in debris.
Management practices for bacterial diseases include use of pathogen-free
or treated seed, crop rotation, field sanitation and use of copper-based
bacteriacides.
Barley Yellow Dwarf Virus
Barley yellow dwarf virus is a luteovirus that infects oats and other
crops. The vector is a number of aphids, including greenbug, bird cherry
oat, corn leaf and English grain aphids. Plants are stunted and have a
stiff, squashed appearance. Tillering is reduced and heads fail to fill.
Individual leaves turn yellow from the tips in a chevron pattern (v-shaped)
that leaves the mid-vein green. The virus survives in aphids, grassy weeds,
volunteers, and in fall-planted cereals. Infected plants are located at
random in a field where the winged adult lands. These plants develop into
the foci of disease. Disease is favored by cool, wet weather in the spring
and early summer. Management depends on late planting of winter cereals
to avoid fall infection or early planting of spring cereals to avoid infection
at early growth stages. There are some sources of resistance in oats.
Loose Smut
Smuts caused by Ustilago, Sphacelotheca and Tilletia
(called
bunts) occur on small grains. Black spore masses replace heads and ears.
Blisters followed by black spore masses appear on leaves and lower scales
of onion. These fungi survive in debris, soil, seed and transplants. Best
management practices include using resistant cultivars, seed treatment
with fungicides, and crop rotation.
Fungicide Matrix
| Captan+Carboxin | |
| Loose Smut | X |
Management:
Fungicides:
Chenopodium album was introduced from Europe, and reproduces
by seeds. The stem is erect, stout, smooth, grooved, often striped with
pink or purple, branched and grows 1 - 6' high. The leaves are alternate
with the lower ones being ovate and upper ones becoming narrower. The flowers
are small, green, and crowded in the axils and at the tips of the stems
and branches. It is a succulent, fast-growing plant which rapidly removes
moisture from the soil.
Kochia
Kochia scoparia, a member of the Goosefoot family, was introduced
from Europe and is an annual, reproducing by seed. The stems are erect,
round, slender, pale green, branched, and 1 - 6' high. Leaves are narrow,
bright green, hairy, numerous and are attached directly to the stem. The
upper leaves are narrow. The flowers are inconspicuous in the axils of
upper leaves. Seeds are about 0.0625" long, wedge-shaped, dull brown, and
slightly ribbed. Kochia can be found throughout the state up to 8,500'.
In autumn the plants may become red and later turn brown, breaking away
from the root, and tumbling over the ground scattering large amounts of
seed.
Russian Thistle
Salsola iberica is a member of the Goosefoot family. It was introduced
from Russia and is an annual which reproduces by seed. It is a round, bushy,
branched plant growing 1 - 3.5' high. The branches are slender, succulent
when young, and woody when mature. The leaves are alternate with the first
ones being dark green, soft, slender, and 1 - 2.5" long. These drop off
and later leaves are short, stiff, spiny, and not over 0.5" long, with
two sharp-pointed bracts at the base. The flowers are small, inconspicuous,
green-white or pink, and are usually solitary in the leaf axils. Seeds
are about 0.0625" in diameter and conical. At maturity, the plant breaks
off at the base and because of its round shape becomes an excellent tumbleweed,
scattering seeds for long distances. It is widespread over Wyoming up to
8,500'.
Sunflower
Helianthus annuus is a native weed. It is an annual, 1 - 10'
tall. Stems are erect, simple to branched and rough. Leaves alternated
and are simple, rough, and are hairy, and have yellow to orange-yellow
ray flowers and brown disk flowers. The flowering season is from July to
September. Seeds are the only source of reproduction.
Wild Buckwheat
Polygonum convolvulus is an annual weed with arrowhead shaped leaves. It has trailing stems, often mistaken for field bindweed, with leaves that are more pointed. Stems can be 8 - 40" long. Clusters of inconspicuous, green flowers form in leaf axils or at the end of stems. Cotyledons are long and broad with a granular bloom and rounded tips. First true leaves are arrowhead shaped with a rough stalk that forms a tight sheath around the stem at the base.
Canada Thistle
Cirsium arvense is a member of the Aster or Sunflower family.
Canada thistle was introduced from Europe and is a creeping perennial which
reproduces by seeds and fleshy, horizontal roots. The erect stem is hollow,
smooth and slightly hairy, 1 - 5' tall, simple, and branched at the top.
The leaves are set close on the stem, slightly clasping, and dark green.
Leaf shape varies widely from oblong to lance-shaped. Sharp spines are
numerous on the outer edges of the leaves and on the branches and main
stem of the plant. The flowers are small and compact, about 0.75" or less
in diameter, and light pink to rose-purple in color, occasionally white.
The seeds are oblong, flattened, dark brown, and approximately 0.125" long.
Canada thistle emerges in April or May in most parts of Wyoming. It is
one of the most widespread and economical damaging noxious weeds in Wyoming.
Because of its seeding habits, vigorous growth, and extensive underground
root system, control or eradication is difficult. It is distributed across
Wyoming from 4,000 - 9,500'.
Pigweed
Amaranthus spp. are weed pests in several cropping systems. A.
hybridus, smooth pigweed was the first triazine resistant plant documented.
A.
retroflexus, redroot pigweed is probably our most common one.
A.lividus,
is a prostrate species with a notch in the tip of the leaf. A. spinosus,
spiny amaranth, has sharp, strong spines on the stem. A. graecizans,
breaks off at the ground line and, because of its round shape, is blown
around by the wind.
Quackgrass
Elytrigia repens is an aggressive perennial grass reproducing
by seed, or spreading by a shallow mass of long, slender, branching rhizomes.
Rhizomes are usually yellowish-white, sharp-pointed, somewhat fleshy. They
are able to penetrate hard soil or even tuber and roots of other plants.
Stems are erect and usually 1 - 3' tall. Leaf blades are 0.25 - 0.5" wide,
flat pointed and have small auricles at the junction of blade and sheath.
Leaf sheath and the upper surface of leaf blades may be thinly covered
with soft hairs. Spikelets are arranged in two long rows, and borne flatwise
to the stem. Florets are awnless, or with short straight awns. These rhizomes
are effectively spread by tillage, increasing the scope of the population
in a field. Tillage is an effective control by depleting food reserves
and bringing rhizomes to the surface.
Tansy Mustard
Descurania pinnata is a native annual which reproduces by seeds.
The plant is covered with fine hairs. The stem is erect, branched and 4
- 30" high. The leaves are alternate, 2 - 4" long, pinnatified to give
a lacy appearance. The flowers are small, pale yellow, and occur in small
clusters at the tips of elongating racemes. It is scattered over Wyoming
up to 8,000'. Tansy mustard spreads by seed from early to late summer.
Wild Oat
Avena fatua is an annual weed, 1 - 4' tall with erect hollow
stems. Leaf blades are 0.125 - 0.625" wide, sheaths open, with membranous
ligules. The seeding leaves twist counterclockwise. The inflorescence is
an open panicle, 4 - 18" long, drooping, spikelets contain 2 - 3 florets
which disarticulate above the glumes. Seeds are yellow to black, narrowly
oval, 0.25 - 0.5" long. This species is distinguished from domestic oats
by the twisted awn which bends at right angles and a horseshoe-shaped scar
at its seed base.
Herbicide Matrix:
| 2, 4-D | Tribenuron-Methyl+Trifensulfuron-Methyl | MCPA | Dicamba | Bromoxynil | Clopyralid+2, 4-D | |
| Bindweed | X | X | X | |||
| Blue Mustard | X | |||||
| Canada Thistle | X | X | X | X | ||
| Kochia | X | X | X | X | X | |
| Leafy Spurge | X | |||||
| Lambsquarters | X | X | X | |||
| Pigweed | X | X | X | |||
| Russian Thistle | X | X | ||||
| Sunflower | X | X | X | X | ||
| Tansy Mustard | X | |||||
| Sago pond weed | X |
Management:
Herbicides:
2,4-D (Weedar 64)
dicamba (Clarity)
glyphosate (Roundup; Roundup RT)
2,4-D + glyphosate (Landmaster BW)
atrazine (Atrazine)
bromoxynil (Bronate; Buctril)
clomazone + atrazine (Command + Atrazine)
dicamba + glyphosate (Fallowmaster)
MCPA (Rhomeme; Amine; Sword; Rhonox LVE)
paraquat (Gramoxone Extra)
picloram (Tordon)
thifensulfron + tribenuron (Harmony)