Soybean Insects

Soybean Insect Identification and Management

Agent Training June 26-27 NCSU and Plymouth, N

Plant Injury Chewing

Piercing-sucking

Insect Mouthparts

Plant Injury Gall making

Insect Vectors

Injury vs. Damage Injury: harm or destruction on the host plant caused by the pest Damage: measurable loss of the host that affects the yield quantity, quality or aesthetics

Old vs. New Injury Old

New

Economic Injury Level EIL: the lowest number of insects that causes economic damage

EIL =

𝐶 𝑉𝐼𝐷𝐾

C = Cost of management per unit area V = market value per unit of product I = Injury units per insect per production unit; expressed as a proportion D = Damage per unit injury K = proportionate reduction in potential injury or damage

Economic Threshold ET = the number of insects that triggers a management action

Corn Earworm/Tobacco Budworm Thresholds now online! www.nccrops.com Will lead to Field Crop Entomology Webpage Link Click Soybean Insect Pests Click Corn Earworm Click CEW Threshold Calculator for Soybeans

Sampling and Monitoring Methods

Direct Sampling Transect

Random Sampling

Seedling Pests • • • • • •

Thrips Grasshopper/Katydid Bean Leaf Beetle Cutworm Threecornered alfalfa hopper Lesser cornstalk borer

Thrips

Tobacco thrips predominate after planting, then soybean thrips Some Eastern flower thrips, very few Western flower thrips

White Margined Burrower Beetle

Grasshoppers

• Most common in reduced till • Adults more difficult to kill

Katydid

Bean Leaf Beetle

Cutworm

Threecornered Alfalfa Hopper

Check when beans are less than 10 inches tall Threshold is one per sweep

Threecornered Alfalfa Hopper Injury

Stem Borers • Lesser cornstalk borer • Dectes stem borer

Lesser Cornstalk Borer

Dectes Stem Borer

Vegetative/Flowering Stage Pests (after seedling stage) • Defoliators – – – – – – – – – – –

Corn earworm/tobacco budworm Armyworm complex Soybean looper (generally late-season) Green cloverworm (generally NOT a pest) Velvetbean caterpillar (generally late-season) Bean leaf beetle Japanese beetle Blister beetle Grape colapsis Spider mites Whitefly

Corn Earworm/Tobacco Budworm

Armyworm Complex

Armyworm Complex

Soybean Looper

Green Cloverworm

Generally NOT a pest

Velvetbean Caterpillar

Four pairs of prolegs

Japanese Beetle

• Beetles often congregate • Damage lacy • Usually sub-economic

Blister Beetle

Grape Colaspis

Spider mites

Whitefly

Defoliator Thresholds • Vegetative stages – 30% defoliation

• Two weeks prior to bloom and during pod-fill – 15% defoliation

Vegetative/Flowering Stage Pests (after seedling stage) Piercing sucking pests –Kudzu bug –Brown stink bug –Green stink bug

Kudzu Bug

Kudzu Bug

Stink Bug Complex

Stink Bug Complex

Green Stink Bug Nymph

Brown Stink Bug Nymph

Piercing/sucking like Kudzu bug

However, stink bugs prefer and damage pods

Common Beneficial Insects • • • • • • •

Ladybird beetle Lacewings Minute pirate bug Bigeyed bug Nabids Spined soldier bug Praying mantis

Ladybird Beetle

eggs

adult

larva

Common NC ladybird beetles

Asian

pink spotted pink spotted

Green Lacewing

adult

larva

eggs

Minute Pirate Bug

Bigeyed Bug

Nabis (damsel bug)

Spined Soldier Bug

Praying Mantis

Reproductive Stage Pests • Defoliators – Soybean looper – Armyworm complex – Bean leaf beetle

• Pod-feeders – Corn earworm/tobacco budworm – Stink bug complex

• Stem feeder – kudzu bug

QUESTIONS?