Small Grain Pests

Aphids

• Order Homoptera   Family Aphididae

• corn leaf aphid and English grain aphid are common aphid pests on small grains in PA.

• Description:corn leaf aphids are blue-green with dark spots around the cornicles. Legs and cornicles are black

• English grain aphids have yellow-green body with black antennae and cornicles

Aphids

General Life History of Aphids

• Aphids have a complex life cycle

• Most overwinter as eggs

• Females hatch from eggs in spring

• Females reproduce parthenogenetically, giving birth to live aphids.

• Several generations per season may be produced this way

General Life History of Aphids

• Eventually some winged progeny are produced

• Winged aphids often migrate to different plant hosts

• Eventually a generation of both males and females are produced

• These aphids mate, and the females lay eggs

Aphid Damage

• Corn leaf aphids and English grain aphids are vectors of barley yellow dwarf virus

• The virus causes plants to turn yellowish and stunts growth

• Aphids can also suck sap from plants and leave brown blotches on the plant

Aphid Damage

Aphid Management

• During the fall, populations of 25 aphids per foot of row is the threshold for treatment. During the spring, populations exceeding 100 per foot of row are needed before treatment is warranted

Armyworm

• Order: Lepidoptera    Family: Noctuidae

• Pseudaletia unipuncta

Armyworm Damage

• Chew on leaves of small grains

• Sometimes cut off the heads of grain

• Cause more damage to barley than wheat

• Armyworms do not cause damage in fields containing only alfalfa or other legumes (this is generally cutworm damage)

Armyworm Damage

Armyworm Management

• Six or more worms per linear foot of drill row is the threshold for treatment

• Control of pest might not be recognized immediately after spraying due to the habits of the insect

Cereal Leaf Beetle

• Order Coleoptera    Family Chrysomelidae

• Oulema melanopus

• Origin: Europe, Middle East, North Africa

• U.S. Distribution: Eastern U.S. and southern Canada

Cereal Leaf Beetle

• Adults approx 4mm long. Black-blue head and elytra. Rest of body is red

• Larvae are yellow with a black head capsule

• Eggs yellow (darken towards time of hatching)

Cereal Leaf Beetle

Cereal Leaf Beetle Life History

• Adults overwinter in plant debris on field ground

• feed on wild grasses in early spring

• move to grain fields later in spring and females lay eggs

• Larval feeding lasts 10 days

• Pupate in soil (below 50mm)

Cereal Leaf Beetle Life History

• Adults emerge in summer and feed a little

• Adults aestivate until fall, at which point they search out a suitable spot to overwinter

Cereal Leaf Beetle Damage

• Adults and larvae feed on the upper leaf surface of young oats

• Both feed on the flag leaf or new growth of winter wheat (larvae are window feeders)

• Tips of damaged leaves turn white

Cereal Leaf Beetle Damage

Cereal Leaf Beetle Management

• Parasitic wasps (5 species) were released by USDA to control outbreaks of CLB

Cereal Leaf Beetle

Hessian Fly

• Order Diptera         Family Cecidomyiidae

• Mayetiola destructor

• Origin: Europe

• Distribution: wheat producing areas of the world

Hessian Fly

• Adults: approx 2.5 mm long, black, look like a mosquito. Gravid females have a red abdomen

• Young larvae are red, but older larvae are white. Green stripe runs longitudinally along the dorsum

Hessian Fly

Hessian Fly Life History

• Larvae overwinter on plant debris

• Pupation occurs in early spring

• Adults emerge between 2 and 3 weeks after pupation

• Adults mate and lay eggs (live only 2-3 days) in the grooves of wheat leaves

• Larvae feed in early summer, pupate in late summer

Hessian Fly Life History

• Adults emerge in fall and lay eggs

• Larvae feed for a short time in fall and then overwinter in puparia

Hessian Fly Damage

• Larvae feed between leaf sheath and stalk, resulting in stunted growth and weakened plants

• A single larva can cause significant damage to a wheat plant because of the salivary toxins released while feeding. These toxins interfere with normal wheat growth

• One leaf stage plants are often killed

• Wheat attacked later may be stunted

Hessian Fly Damage

Hessian Fly Management

• Cultural practices can help to reduce population numbers, esp. destruction of volunteer wheat

• Delayed planting

• Use of resistant wheat varieties

• Insecticides are rarely recommended because of the sporadic nature of severe Hessian fly infestations

• Two parasitic wasps are natural enemies of the Hessian fly

Hessian Fly Management

Grasshoppers

• Order Orthoptera  Family Acrididae

• Description: (differential grasshopper)1.5 to 1.75 inches long, yellowish with brown and black markings and black markings on hind legs

Grasshopper

Grasshopper Life History

• Overwinter as eggs

• hatch in early spring (after adequate rainfall is received)

• nymphs move to areas of plentiful food resources

• Adults appear after 5 to 6 nymphal molts

• Adults mate and females lay eggs

Grasshopper Damage

• Feed on outer edges of leaves

• Attack all types of field crops

Grasshopper Management

• Grasshoppers have multiple natural enemies, including flesh flies, bee flies, blister and ground beetles, spiders

• Tilling the soil can kill grasshoppers in the egg stage