PESTS OF FIELD CROPS

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PESTS OF FIELD CROPS IN WYOMING
PESTICIDE SAFETY AND APPLICATION PLNT 1150
Alex Latchininsky Assistant Professor / Extension
Entomologist Dept. of Renewable
Resources January 2006
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DISCLAIMER Trade or brand names used in this
presentation are used only for educational
purposes The information given herein is
supplied with the understanding that no
discrimination is intended, and no endorsement
information of products is implied
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I. PRINCIPLES OF FIELD CROP INSECT CONTROL

• You must know
• Basics of insect classification and biology
• Crop value
• Preventive measures
• Whats new?

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II. WHAT CAUSES INSECT OUTBREAK?
It can be weather, but
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• Frequently its our own fault
• Large-scale monocultures
• Poor cultural practices
• Overuse of insecticides (killing natural
  enemies)
• Pest introduction in the new environment
• Disruption of a natural equilibrium

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III. TYPES OF CONTROL

• 1. Biological
• Introduction of exotic species of parasites and
  predators
• Conservation of parasites and predators
• Augmentation of parasites and predators
• Microbiological control (pathogens)
• Drawbacks may be costly often slow
  and weather-dependent

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Biocontrol agents
Ladybird beetle larva and adult Pathogens
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TYPES OF CONTROL

• 2. Mechanical
• Hand picking
• Trapping
• Using devices like screens and barriers
• Drawbacks time- and labor-consuming, slow, often
  impractical at large-scale

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TYPES OF CONTROL

• 3. Cultural
• Crop rotation good for insects with long life
  cycles (e.g., corn rootworms)
• Trap crops attracts pests then the trap crop
  is destroyed or treated with insecticide
• Tillage good for soil-inhabiting insects
• Clean culture removal of crop residues
• Timing of planting and harvesting
• Resistant plant varieties, including genetically
  modified cultivars

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• Cultural control advantages
• Normal farming practices, making environments
  unfavorable for pests
• Preventive strategy
• Economical
• Good for low-unit-value crops
• Cultural control drawbacks
• Will not work in an outbreak situation when
  pest infestation is heavy

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TYPES OF CONTROL
4. Chemical Reduction of insect populations or
prevention of insect injury by the use of
materials to poison them, attract them to other
devices, or repel them from specific areas Still
our first line of defense despite adverse
publicity
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• Chemical control advantages
• Efficient
• Economical
• Fast-acting
• Easy to use
• Generally safe

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• Chemical control drawbacks
• Temporary relief
• May cause resistance
• Residues in harvest
• Environment side-effects to non-targets
• Some insecticides have direct hazards

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TYPES OF CONTROL
5. Integrated (IPM) Management of insect
populations by the utilization of all suitable
techniques in a compatible manner so that damage
is kept below economic levels Ecological
approach to avoid economic losses and to minimize
adverse effects
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IV. MAJOR FIELD CROP PESTS
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PESTS OF CORN
Western Corn Rootworm Northern Corn
Rootworm Southern Corn Rootworm Spider (Banks
grass) mites
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Western Corn Rootworm
adult
larva
Diabrotica virgifera - beetle

• The larvae attack the roots, causing the plants
  to fall over and become goose-necked.
• The adults feed on the silks and, at times,
  become so numerous that pollination cannot
  occur.
• Overwinter as eggs in the soil. One generation
  per year.

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Western Corn Rootworm

• Control
• The most effective means of control is by crop
  rotation. Corn grown year after year on heavy
  soil is the most seriously damaged.
• Pesticides do not use when rotating crops. If
  necessary, apply granules in a 6-7 inch bank over
  the row at planting time or as a cultivation
  treatment.
• Do not apply sprays for adults unless
  pollination is threatened.

Heavy root damage
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Northern Corn Rootworm

• Yellowish-green 3/16 to 1/4 inch (5 to 6 mm)
  long, slightly smaller than the western and
  southern corn rootworms.
• There are no markings on the elytra.

Diabrotica barberi - beetle

• Adults are found on the silks of corn. Like the
  western corn rootworm, this species overwinter as
  eggs, which are deposited in cornfields. The
  adults are common on goldenrod flowers.
• Control Similar to Western corn rootworm.

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Southern Corn Rootworm

• Pale greenish-yellow beetle with six black spots
  on each wing cover.
• Slightly bigger than WCRW and NCRW.
• Occurs commonly on cucumber, melon vines, corn
  silk, weeds, and in alfalfa fields.
• Overwinter as adults. May have two or more
  annual generations.
• Other name spotted cucumber beetle.

Diabrotica undecimpunctata - beetle
Damage The larvae damage roots of corn and
winter rye, and adults eat holes in melon
foliage. Adults spread bacterial wilt to
cucumbers. Control Similar to WCRW and NCRW.
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Spider mites
Size lt1/32 8 legs
Twospotted spider mites Tetranychus urticae
Banks grass mites Oligonychus pratensis

• Overwinter as adults in debris. Several
  generations per year.
• Damage pierce plant cells and suck out liquid
  contents. Leaves develop chlorotic spots and may
  die back. Start feeding on the lower leaves and
  move upward. Hot, dry conditions are favorable.
• Control systemic insecticides.

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PESTS OF ALFALFA
Alfalfa weevil Pea aphid Lygus bug Blister beetles
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Alfalfa weevil
Hypera postica - beetle

• The color is brown with a darker brown stripe
  down the middle of the elytra.
• The pronotum has a dark brown stripe through
  which runs a pale line.
• Adult length is about 1/4 inch (6 mm).

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Alfalfa weevil
Eggs Larvae

• Larva is green or yellow with dark head.
• Damage mostly by larvae. Skeletonize leaves.
  Feed on the foliage, especially terminal leaf
  buds, then drop to the ground and pupate in the
  litter.
• Adults overwinter. One generation per year.

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Alfalfa weevil
Leaf skeletonization by larvae

• Cultural management Early first harvest fall
  grazing spring burning resistant cultivars.
• Chemical control Mostly organophosphates, which
  are highly toxic for pollinators (bees) and
  other beneficials. Apply early in the morning
  or late in the evening.

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Pea aphid
Acyrthosiphon pisum

• Green, long-legged, about 1/6 long.
• Many generations per year.
• Overwinter as eggs or adult females.

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Pea aphid

• Damage Suck the sap. Cause wilting and reduce
  quality and quantity of alfalfa hay.
• Control preferably systemic insecticide sprays.
  Apply when Tgt50F early in the morning or
  late in the evening to preserve the beneficials.
  

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Lygus bug
Lygus lineolaris true bug

• Adults ¼ long, variable in color. Distinct
  V on the back. Piercing-sucking beak.
• Overwinter as adults. Three generations per
  year.

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Lygus bug
Lygus bug larvae

• Damage Most serious in seed production. Cause
  buds to die, flowers to drop, immature seeds to
  shrivel. Forage production and quality also
  affected.
• Control Systemic insecticides and carbaryl.
  Non- targets (predators, parasites and
  pollinators) are a great concern. Timing of
  application is important.

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Blister beetles
Toxic chemical cantharidin can make hay poisonous
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PESTS OF DRY BEANS
Mexican bean beetle
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Mexican bean beetle
larva
adult
Epilachna varivestis a ladybird beetle

• Adults are red with 16 black spots, ¼ long.
• Larvae are yellow with branched spines, up to ¼
  long.
• Overwinter as adults in litter. One generation
  per year.

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Mexican bean beetle
Damage Both adults and especially larvae chew
off portions of leaves. They usually feed by
clinging to the under surface of the leaves and
eating irregular sections of the lower leaf
surface. The upper surface of leaves quickly
dries out, giving a lace-like, skeletonized
appearance.
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Mexican bean beetle
Control Cultural burning or destruction of
crop residues Resistant varieties (e.g., Lima
beans) Biological several species of
parasitoids available Chemical systemic and
non-systemic insecticides, soil applications and
foliar spray. Difficult to control because feed
underneath the leaves.
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PESTS OF SUGAR BEETS
Sugar Beet Root Maggot Beet Leafhopper
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Sugar Beet Root Maggot
adult fly
larva (maggot)
Tetanops myopaeformis a true fly

• Overwinters as a larva (maggot) in the soil.
• Adult flies emerge in May.
• Females deposit eggs around the base of sugar
  beet plant.
• One generation per year.

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Sugar Beet Root Maggot
Damage maggots attack seedlings and cause loss
of stand. Yields are reduced. Control only
larval control is recommended. Apply granules
to the soil as a 4-6 band over the row.
Granules must have moisture to be activated.
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Beet Leafhopper
adult
nymph
Circulifer tenellus

• Overwinter as adults in weedy areas. Host
  plants include wild mustards, Russian thistle and
  other weeds.
• Eggs hatch and nymphs move into beet fields.
• One or more generations per year.

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Beet Leafhopper
Damage vector of the virus causing the disease
curly top in sugar beets. Control Cultural
Weed management. Resistant varieties. Chemical
granulated formulations to the soil. Moisture
is necessary to activate the granules.
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PESTS OF POTATOES
Potato Psyllid Colorado Potato Beetle Potato Flea
Beetle
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Potato Psyllid
adult
nymphs
Bactericerca (Paratrioza) cockerelli

• Related to aphids and leafhoppers. The adult has
  clear wings that rest rooflike over the body.
  Predominantly black, with white markings. Scale
  like flat nymphs. Psyllids jump quite readily
  when disturbed.
• Overwinter as eggs. Several generations per
  year.

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Potato Psyllid
Damage nymphs inject toxin when feed causing
psyllid yellows and upward curling of
leaves. Control granular systemic insecticides
at planting time. Foliar spray of synthetic
pyrethroids.
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Colorado Potato Beetle
Leptinotarsa decemlineata
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Colorado Potato Beetle
adult and eggs
larvae

• Overwinters as an adult buried in soil.
• Eggs hatch in the spring. Larvae feed on
  foliage.
• One or two generations per year.

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Colorado Potato Beetle
Damage both larvae and adults are voracious
feeders. They often completely defoliate potato
plants. Control systemics in the soil at
planting time. Foliar spray after egg hatch.
Resistance may be an issue.
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Potato Flea Beetle
Epitrix cucumeris

• Adult beetle is 1/16 long and black in color.
• Has enlarged hind legs and jumps vigorously when
  disturbed.
• Overwinters as an adult in soil litter. One or
  two generations per year.

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Potato Flea Beetle

• Damage destroys foliage. Spreads a fungal
  disease - early potato blight.
• Control Cultural destruction of plant
  residues. Weed control. Late planting.
• Chemical systemic insecticides to the soil at
  planting time. Foliar spray with contact
  insecticides against larvae.

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PESTS OF SMALL GRAINS
Pale Western Cutworm Western Curl Mite Russian
Wheat Aphid Greenbugs Grasshoppers
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Pale Western Cutworm
larva
adult
Agrotis orthogonia miller moth

• Eggs are laid in the soil in the fall.
• Overwinter as eggs. Hatch very early in
  spring.
• One generation per year.

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Pale Western Cutworm

• Larvae feed mostly underground.
• Cause pruning of plants, loss of stand, and
  stunted and unthrifty plants.

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Wheat Curl Mite
Eriophyes tulipae

• The mites are very tiny, white, spindle-shaped,
  with 4 legs near the anterior end.
• Reproduce parthenogenetically (without males).
• Overwinter on grasses or volunteer wheat.

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Wheat Curl Mite
Damage Transmits a viral disease called wheat
streak mosaic. This virus can cause serious
reductions in wheat crop yields. Although the
mites feed on a variety of grasses, wheat is the
preferred host and high populations can develop
during the summer and fall on volunteer wheat.
Control Cultural - prevent the growth of
volunteer wheat. Late planting. Resistant
cultivars. Chemicals are rarely effective.
Hail belt areas are in greatest need of
protection.
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Russian Wheat Aphid
Diuraphis noxia

• Native to southern Russia and the Mediterranean
  region.
• Introduced in the U.S. in 1986.
• Reproduces sexually or asexually.
• Several generations per year.
• Overwinter as immatures or adults in grasses.

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Russian Wheat Aphid
Soybean Aphid
Russian Wheat Aphid identification characteristics

• Elongated
• Short antennae
• No cornicles (tail-pipes)
• Forked (double) tail

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Russian Wheat Aphid

• Damage
• RWA initiates feeding at the base of the leaves
  near the top of the plant. It injects a toxic
  saliva into the plant. The edges of the leaf
  curl inward protecting the pest.
• Plants become purplish and leaves develop
  longitudinal yellowish and whitish streaks.
• Tillers of heavily infested plants run parallel
  to the ground (a prostrate appearance).
• Heads are distorted.

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Russian Wheat Aphid

• Control
• Cultural control volunteer wheat avoid early
  planting use resistant varieties maintain
  healthy stand.
• Biological parasitic wasps, ladybird beetles.
• Chemical foliar sprays with systemics.

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Greenbug aphids
Inject toxin when feed. Cause greenbug
spots. Control systemic insecticides.
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Grasshoppers in the West

• economically important in 17 western states
• a dozen pest species (out of gt450)
• annually remove 20-22 of rangeland vegetation
• estimated average loss 400 million per year
• forage losses in 2000 in Texas 190 million

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2005 Rangeland Grasshopper Hazard Map Based on
adult Survey 2004
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Grasshoppers
112 species in Wyoming only 10 are serious pests
Differential
Migratory
Twostriped ?
Twostriped ?
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(No Transcript)
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Mormon cricket
is neither a grasshopper nor a cricket its a
katydid
Anabrus simplex
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Grasshoppers in Wyoming

• require vast areas to be chemically treated
  (up to 20 million ac per year during
  outbreaks)
• 400,000 acres protected in 2003 in Wyoming
  (Niobrara, Goshen, Platte and other counties)
• Reduced Agent and Area Treatments - RAATs

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Grasshopper Outbreak Frequency 1944-1996
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2005 Rangeland Grasshopper Wyoming Hazard
Map Based on adult Survey 2004
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LIFECYCLE
V
Duration of nymphal period 30-40 d
IV
III
1st instar - critical stage for GH survival
(up to gt90 mortality)
II
I
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Grasshopper Treatment Application Strategies
Conventional/Blanket RAATs
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THE RAATs CONCEPT

• Hoppers killed directly in the treated swaths
• More predacious insects and parasitoids survive
  treatment
• Hoppers move into treated strips and die
• Birds continue to feed on hoppers
• Less disruption to bio-control agents of weeds
  (APHIS data on Aphthona spp. beetles on leafy
  spurge in Montana)

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ATV- RAATs
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Boom Buster nozzles
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S.S. Co. ¼-KLC- 5 Fieldjet nozzles

• Half rate of Boomless type _at_ 2 Qt/min
• Low cost and simplicity
• 17-21 ft swath

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RAATsAerial ATV
treated
untreated
100 ft
100 ft
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Malathion (Fyfanon)
Organophosphate neurotoxin (AcChE inhibitor)
PROS Low cost/unit ULV logistics Reliable
results Familiar product (since 1965) CONS
Hot weather rain Low residual (no
RAATs) Non-target effects Harm to people
and planes Organophosphates phasing out
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Carbaryl (Sevin XLR Plus)
Carbamate neurotoxin (AcChE inhibitor)
PROS Temperature Range Some Residual
(RAATs) Reliable Results Easy Handling
(water based) Familiar product (since
1979) CONS Higher Volume Non-target
effects Harm to people
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Diflubenzuron (Dimilin 2L)
Benzoyl-Urea IGR (chitin synthesis inhibitor)
PROS Safety (bees, people, etc.) Residual
(RAATs) Reliable Results Temperature
Range CONS Timing!!! (IGR nymphs) Less
Familiar (since ) High Cost/unit Harm to
aquatic invertebrates R.U.P.
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MOLT
Insects are killed when they grow to a next
developmental stage
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TIMING is critical when applying Dimilin
V
not recommended
ineffective
IV
III
recommended
II
I
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Risks for Different Groups of Non-target
Organisms
Source Food and Agriculture Organization of the
UN, 2003
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Environmental Profile
Carbaryl Malathion Diflubenzuron
CAR OP BU (IGR)
Human toxicity (WHO/EPA class) II
(Moder.) III (Low) Unlikely to
be toxic Fish toxicity
Moderate Low
Low Aquatic
invertebrate toxicity Low
Moderate High
Mammalian toxicity Moderate
Low Low
Toxicity for birds and reptiles
Low Moderate
Low Toxicity for honey
bee High High
Low Toxicity for
other non-target arthr. High
Moderate Moderate

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RAATs vs. Standard Efficacy
Control is 5 to 15 lower than conventional
blanket methods (usually about 80 kill)
It costs a lot to kill them all. Surviving
grasshoppers provide a prey base for the
predators. We havent observed any resurgence
the following year in treated areas.
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RAATs COSTS 50-60 less than the standard
treatment about 1.50 / acre protected
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Other Options
Carbaryl bran baits Pros Target
specificity Operator safety Enhanced
formulations Cons Application logistics and
cost Species constraints (not all species take
them) Adverse conditions Systemics applied in
the furrow at planting
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RAATs the preferred option for USDA grasshopper
treatments in recent EIS
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Decision-Support software
2005 Crop protection module added
CARMA can be downloaded from Grasshoppers of
Wyoming and the West at www.wygisc.uwyo.edu/gras
shopper/ or request a free CD-ROM Grasshoppers
Their Biology, Identification and Management
from www.sidney.ars.usda.gov/grasshopper/
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Pest Control in Wyoming
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Fine trophies guaranteed!
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• Come catch the Entomology Short Course, 2006
• February 1-3, 2006
• What will be covered? General Entomology,
  Insect Identification, Arachnids, Grasshopper
  Management, Biological Control, Mosquitoes,
  RS-GIS and more.
• When is it? February 1st, 2nd, and 3rd, 2006.
  We will begin at 1 PM on the first day, go from 8
  to 5 the second day and release you at noon on
  the third day.
• Where is it? College of Agriculture Building,
  13th Lewis St., University of Wyoming, Laramie,
  WY.
• Who teaches it? Dr. Alex Latchininsky Scott
  Schell, UW-CES Extension Entomologists. Plus
  guest lectures by other experts in their fields.
• You will get two books, a course packet, and 2
  hours of college credit for as little as a 100
  (maybe less)

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Questions? Contact Alex Latchininsky or Scott
Schell, Uwyo Extension Entomologists Phone
766-2298 or 766-2508 Email latchini_at_uwyo.edu or
sschell_at_uwyo.edu http//uwadmnweb.uwyo.edu/UWCES/
Entomology.asp