Forage Pests
Alfalfa Weevil
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Order
Coleoptera Family
Curculionidae
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Hypera
postica
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Origin:
Southern Europe
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N.A.
Distribution: throughout U.S. and parts of Canada and Mexico
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Description:
Adults <5mm long. Brown w/ dark brown stripe on back.
Larvae pale green w/ black headcapsule.
Alfalfa Weevil
Alfalfa Weevil Larva
Alfalfa Weevil Life History
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Adults
overwinter in plant debris along field edges
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Adults begin
to feed in early spring on alfalfa leaves
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Between April
and May, a female oviposits 400 -1000 eggs
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After 3rd
molt, larvae spin cocoons attached to alfalfa leaves or plant debris
Alfalfa Weevil Life History
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7-14 days:
Adults emerge and feed briefly
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Adults
aestivate for the remainder of the summer
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Adults become
active in fall only to prepare for winter diapause
Alfalfa Weevil Damage
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One of the
most serious alfalfa pests in the U.S.
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Most damage
is to 1st growth alfalfa
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Larvae
feeding on the developing buds and leaves cause damage to top growth
Alfalfa Weevil Damage
Alfalfa Weevil Management
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Factors which
favor increased weevil numbers: overuse of insecticides which wipe out
natural enemies, mild winters and dry springs
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Parasitic
wasps and various fungi are often used to control alfalfa weevil numbers
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Remove plant
material from the ground around the field
Clover Root Curculio
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Order
Coleoptera Family
Curculionidae
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Sitona
hispidula
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Distribution:
Throughout the U.S. and southern Canada
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Description:
5mm long, shiny black or brown with gray underside. Three stripes of copper
or gray color on back. Larvae are gray-white with brown head capsule
Clover Root Curculio
Clover Root Curculio Larvae
Clover Root Curculio Life History
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Overwinter as
adults, eggs, or small larvae
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Larvae feed
on root nodules in spring
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older larvae
feed on lateral and main tap roots
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Pupation
occurs in early April.
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Adults emerge
in May or June
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Females lay
approx 500 eggs into plant crowns in October and November or the following
spring
Clover Root Curculio Damage
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Larval
feeding on roots weakens plants and allows for easier entry of disease
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Adults feed
on leaves, leaving small notches on the edges
Clover Root Curculio Management
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Crop rotation
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Plowing
during late fall or early spring
Pea Aphid
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Order
Homoptera Family
Aphididae
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Acyrthosiphon
pisum
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Distribution:
throughout U.S. and Canada in pea and alfalfa growing regions
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Description:
adults are green with red eyes, Approx 2-4mm long, cornicles long and
slender
Pea Aphid
Pea Aphid Life History
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Wingless
females often feed and reproduce during winter, with an increase in feeding
in the spring
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winged aphids
often develop and migrate in the spring
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Adult females
produce up to 100 offspring, generally 6-8 nymphs per day
Pea Aphid Damage
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Pea aphids
feed on terminal leaves and stems of their host plants
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Feeding leads
to wilting, deformation of plant, or death.
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Brown or
yellow spots often appear on leaves fed upon
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Transmit pea
enation virus and yellow bean mosaic virus
Pea Aphid Damage
Pea Aphid Management
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Cutting
during early bloom stage reduces numbers
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Plant
resistant varieties, if available
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Natural
enemies often keep populations down
Potato Leafhopper
Potato Leafhopper Damage in Alfalfa
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Often become
problems in areas and/or during times of high rainfall and humidity
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Nymphs cause
most serious damage
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Feeding can
be recognized by a wedge shaped yellow area on leaf tip (hopperburn)
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Stunting of
plant growth may occur
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New spring
seedlings are most vulnerable
Potato Leafhopper Management in Alfalfa
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Monitoring
population numbers is important
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Outbreaks are
often controlled through chemical application
Alfalfa Blotch Leafminer
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Order Diptera
Family Agromyzidae
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Agromyza
frontella
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Distribution:
First introduced to U.S. in 1968 (Massachusetts)
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Description:
Adult approx 0.1 inches long and looks like a housefly. Maggots are light
yellow
Alfalfa Blotch Leafminer Life History
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In PA there
are at least three generations per year
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Adults emerge
in spring. Females cut holes in the lower leaf surface and lay eggs under
the leaf epidermis (1-3 eggs per leaflet)
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Larvae tunnel
into leaf and feed on leaf tissue
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Larval stage
lasts approx. 2 weeks
Alfalfa Blotch Leafminer Damage
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White
blotches on leaflets indicate larval mining (often comma shaped)
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Decrease in
foliage quality, defoliation, and loss of photosynthetic area due to
blotches and punctures
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Second
cutting is often most seriously damaged
Alfalfa Blotch Leafminer Damage
Alfalfa Blotch Leafminer Management
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Introduced
parasitic wasp keeps this insect’s population densities below economic
threshold most of the time (Dacnusa dryas)
Meadow Spittlebug
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Order
Hemiptera Family
Cercopidae
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Philaneus
spumarius
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Distribution:
In the U.S. along the Pacific Coast, and from Louisiana to Minnesota
eastward
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Description:
Adults are variably colored (gen. Brown or tan), leafhopper-like in shape.
Nymphs are often yellow or pale green in color
Meadow Spittlebug
Meadow Spittlebug Adult
Meadow Spittlebug Life History
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Overwinter as
egg masses in the stem and leaf sheath
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Eggs hatch
around April
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Nymphs feed
for approx. 1 month before becoming adults
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Females
deposit eggs in August and September
Meadow Spittlebug Damage
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Wilted and
stunted plant growth
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Yield
reduction if spittlebug numbers are high (more than 100 bugs/plant)
Meadow Spittlebug Management
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Heavily
infested fields (50 to 100 spittle masses per plant) should be sprayed to
kill adults and reduce the following year’s nymphal population