Forage Pests

Alfalfa Weevil

• Order Coleoptera   Family Curculionidae

• Hypera postica

• Origin: Southern Europe

• N.A. Distribution: throughout U.S. and parts of Canada and Mexico

• 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

• Adults overwinter in plant debris along field edges

• Adults begin to feed in early spring on alfalfa leaves

• Between April and May, a female oviposits 400 -1000 eggs

• After 3rd molt, larvae spin cocoons attached to alfalfa leaves or plant debris

Alfalfa Weevil Life History

• 7-14 days: Adults emerge and feed briefly

• Adults aestivate for the remainder of the summer

• Adults become active in fall only to prepare for winter diapause

Alfalfa Weevil Damage

• One of the most serious alfalfa pests in the U.S.

• Most damage is to 1st growth alfalfa

• Larvae feeding on the developing buds and leaves cause damage to top growth

Alfalfa Weevil Damage

Alfalfa Weevil Management

• Factors which favor increased weevil numbers: overuse of insecticides which wipe out natural enemies, mild winters and dry springs

• Parasitic wasps and various fungi are often used to control alfalfa weevil numbers

• Remove plant material from the ground around the field

Clover Root Curculio

• Order Coleoptera   Family Curculionidae

• Sitona hispidula

• Distribution: Throughout the U.S. and southern Canada

• 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

• Overwinter as adults, eggs, or small larvae

• Larvae feed on root nodules in spring

• older larvae feed on lateral and main tap roots

• Pupation occurs in early April.

• Adults emerge in May or June

• Females lay approx 500 eggs into plant crowns in October and November or the following spring

Clover Root Curculio Damage

• Larval feeding on roots weakens plants and allows for easier entry of disease

• Adults feed on leaves, leaving small notches on the edges

Clover Root Curculio Management

• Crop rotation

• Plowing during late fall or early spring

Pea Aphid

• Order  Homoptera   Family  Aphididae

• Acyrthosiphon pisum

• Distribution: throughout U.S. and Canada in pea and alfalfa growing regions

• Description: adults are green with red eyes, Approx 2-4mm long, cornicles long and slender

Pea Aphid

Pea Aphid Life History

• Wingless females often feed and reproduce during winter, with an increase in feeding in the spring

• winged aphids often develop and migrate in the spring

• Adult females produce up to 100 offspring, generally 6-8 nymphs per day

Pea Aphid Damage

• Pea aphids feed on terminal leaves and stems of their host plants

• Feeding leads to wilting, deformation of plant, or death.

• Brown or yellow spots often appear on leaves fed upon

• Transmit pea enation virus and yellow bean mosaic virus

Pea Aphid Damage

Pea Aphid Management

• Cutting during early bloom stage reduces numbers

• Plant resistant varieties, if available

• Natural enemies often keep populations down

Potato Leafhopper

Potato Leafhopper Damage in Alfalfa

• Often become problems in areas and/or during times of high rainfall and humidity

• Nymphs cause most serious damage

• Feeding can be recognized by a wedge shaped yellow area on leaf tip (hopperburn)

• Stunting of plant growth may occur

• New spring seedlings are most vulnerable

Potato Leafhopper Management in Alfalfa

• Monitoring population numbers is important

• Outbreaks are often controlled through chemical application

Alfalfa Blotch Leafminer

• Order Diptera   Family  Agromyzidae

• Agromyza frontella

• Distribution: First introduced to U.S. in 1968 (Massachusetts)

• Description: Adult approx 0.1 inches long and looks like a housefly. Maggots are light yellow

Alfalfa Blotch Leafminer Life History

• In PA there are at least three generations per year

• Adults emerge in spring. Females cut holes in the lower leaf surface and lay eggs under the leaf epidermis (1-3 eggs per leaflet)

• Larvae tunnel into leaf and feed on leaf tissue

• Larval stage lasts approx. 2 weeks

Alfalfa Blotch Leafminer Damage

• White blotches on leaflets indicate larval mining (often comma shaped)

• Decrease in foliage quality, defoliation, and loss of photosynthetic area due to blotches and punctures

• Second cutting is often most seriously damaged

Alfalfa Blotch Leafminer Damage

Alfalfa Blotch Leafminer Management

• Introduced parasitic wasp keeps this insect’s population densities below economic threshold most of the time (Dacnusa dryas)

Meadow Spittlebug

• Order Hemiptera   Family Cercopidae

• Philaneus spumarius

• Distribution: In the U.S. along the Pacific Coast, and from Louisiana to Minnesota eastward

• 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

• Overwinter as egg masses in the stem and leaf sheath

• Eggs hatch around April

• Nymphs feed for approx. 1 month before becoming adults

• Females deposit eggs in August and September

Meadow Spittlebug Damage

• Wilted and stunted plant growth

• Yield reduction if spittlebug numbers are high (more than 100 bugs/plant)

Meadow Spittlebug Management

• Heavily infested fields (50 to 100 spittle masses per plant) should be sprayed to kill adults and reduce the following year’s nymphal population