Transcript True Armyworm - LSU AgCenter

Wheat Insect Pest
Management
by
Dr. Jack Baldwin
Dept. of Entomology
LSU AgCenter
True Armyworm
Fall Armyworm
Both have four abdominal prolegs and are about 1.5 inches in length when full grown.
Fall Armyworm
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Reported to be a pest on
seedling wheat in the fall.
Brownish color, but varies
from green to almost black.
Dark head with prominent
inverted Y on front.
Spines and hairs on body.
4 black spots arranged in
square on top of 8th
abdominal segment.
Worm Damage to Seedling Wheat in Fall
Suspected Pest/s: Fall Armyworm and Cutworm
Stand loss (November)
Clipped seedlings
True Armyworm
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Greenish color, but varies.
Brownish head with
honeycombed markings.
Smooth body, no hairs or
spines.
Orange stripes on both
sides of body.
Each proleg has brownish
or dark colored band on
outer sides.
True Armyworm
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Primarily an early season (spring) pest.
Strong preference for grass crops:
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Known to infest wheat and corn in LA
Source of infestation:
Overwinters in larva stage
 Migration
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Life cycle: egg to adult requires 41-66 days.
Eggs laid in masses of 25 or more
True Armyworm
Observations and Conventional Trends
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Bigger problem in cool, wet springs
Prefers fields with lush, rank growth and lodging.
Moth like to lay eggs in moist shady areas.
In LA, infestations usually develop in April.
Feeds at night. During day it hides under soil or
under surface debri and thatch.
Scout for pest during early am and late pm, or look
for larvae on and under the ground surface.
Feeds on foliage. Appears as notches on leaf
margin, or in extreme cases complete defoliation.
Frass appears as black, pepper-like droppings.
Feeding on the heads (beards) and/or clipped
heads
True Armyworm
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When to treat: 5 or more larvae per square foot and
foliage loss is occurring.
Protect crop/foliage until physiological maturity
(hard dough stage).
Head clipping:
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Theory 1: Clip heads after defoliating
leaves.
Theory 2: Some years heads clipped
and some years they are not.
Suggested threshold of 2-3% clipped
heads.
Stink Bugs
Rice Stink Bug and Southern Green Stink Bug
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Occasional pest, more so
in south LA.
Damage developing seed
grain with piercingsucking mouthparts.
At milk stage or earlier
(flowering): treat when
10% of seed heads have
stink bugs.
At soft dough stage, treat
when 25% of seed heads
have stink bugs.
Aphids
English grain aphid
Oat bird cherry aphid
Corn leaf aphid
Yellow sugarcane aphid
Greenbug
Russian wheat aphid
Aphids
General Biology
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Generation – about a week
from birth to mature aphid
Adult females give birth to
living young; 2-3 per day
for 2-3 weeks
Piercing-sucking
mouthparts; remove plant
juices
Winged or wingless
Soft bodied insects
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Identification
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Legs
Antennae
Siphunculi (cornicles)
Aphids
Potential pests, but normally not a major problem in LA.
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Inject Toxin
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Russian wheat aphid –
does not occur in LA.
Greenbug – usually
does not develop high
populations.
Yellow sugarcane aphid
– Not as toxic to wheat
as to sorghum.
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Do Not Inject Toxin
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Corn leaf aphid
Oat bird cherry aphid
English grain aphid –
clusters on grain heads.
Transmit BYDV
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Corn leaf aphid
Oat bird cherry aphid
English grain aphid
Greenbug
Oat Bird Cherry Aphid
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Color ranges from green to
black
Tips of siphunculi, legs
and antennae are black.
Reddish-orange colored
patch on rear of abdomen
Direct feeding usually not
damaging
Corn Leaf Aphid
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Blue green color; can
appear black
Black siphunculi, legs
and antennae
More common on
grain sorghum than
wheat
Direct feeding usually
not a problem.
English Grain Aphid
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Long, black siphunculi
Black antennae that
extend straight back over
the abdomen.
Dark legs or leg bands
Direct feeding can cause
damage; usually in flowering/
early grain formation.
Dark hit areas in field from flag
leaf damage and fungal infected
heads.
Thresholds are available in
some states.
Greenbug
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Light green with dark
green stripe down the back
Dark tips on siphunculi
(tail pipes) and legs
Present in wheat all winter
and can reproduce at
temperatures lower than
natural enemies.
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Injects toxin; results in
yellowish spot with dark
lesion; ultimately death.
Damaged areas first
appear as N deficiency/
moisture stress.
Yellow Sugarcane Aphid
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Long, oval, hairy body
shape.
Lemon yellow to mint
green color
Siphunculi, legs and
antennae are light colored.
Injects toxin and can cause
serious damage.
More damaging to grain
sorghum than wheat.
Russian Wheat Aphid
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Present in 16 western states on wheat and barley
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First US detection was in Muleshoe, TX in 1986
Aphid Mummies
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Aphids that have been
parasitized by small
wasps.
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Greenbug mummies
Hessian Fly
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Important pest of wheat, but
rarely a problem in the deep
south states.
Outbreaks in the southeast in
1984-1985 and 1985-1986.
Outbreak in Alabama in 1989.
Detected in southwest
Alabama in 2006.
Detected in collections taken
from Louisiana in 2000.
Larva (Maggot)
Pupa (Flaxseed)
Insecticide Seed Treatments
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Gaucho and Cruiser have wheat labels.
Labeled for aphid control and Hessian fly
control
No current LA data at this time to support their
use, but they will be looked at this year.
Questions