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Key Points:
- Soybean aphids are small insects that use piercing-sucking mouthparts to remove plant sap.
- Infested fields should be scouted frequently.
- Foliar insecticides can be used to manage soybean aphids when populations surpass economic thresholds.
Pest Facts and Impact on Crop
- Latin name is Aphis glycines Matsumura.
- Origin in Asia.
- First detected in U.S. near Lake Michigan in 2000.
- Major outbreaks in 2001, 2003, and 2005.
- Untreated economic infestations frequently reduce yields by more than 10 bu/acre.
- Development
- Overwinter on buckthorn, move to soybeans in July and back to buckthorn in the fall.
- Host plants include a wide range of legumes (soybean, alfalfa, clovers).
Causes of Yield Reduction
- Removal of moisture, nutrients needed for grain production
- Honeydew on leaves where sooty mold grows, which reduces photosynthesis
- Transmission of viruses
Soybean aphid distribution and area of increased probability of economic infestation.
Pest Symptoms/Injury ID
- Shortened plant height.
- Curled leaves, often yellow on outside (similar to potassium deficiency).
- Excessive honeydew on leaves, which promotes sooty mold.
- Presence of ants, which also feed on the honeydew.
Natural Enemies
- Asian lady beetle – adult or larvae.
- Chrysopa/Lacewing – adult or larvae.
- Syrphid fly – larvae.
- Predatory bugs – Minute pirate bug, Big-eyed bug, Damsel bug, etc.
- Bio-control agent: Parasitic wasp – Binodoxys communis.
- Various fungal diseases
Pest ID
- Soybean aphids are small
- Less than 1 mm in length
- Oval or pear-shaped
- Color is typically light green
- Adults may or may not have wings
- Winged adults have black head/thorax
- Cornicles are distinguishing characteristic
- Black "tail pipes" projecting from the rear of the abdomen
- Aphids develop by gradual metamorphosis in three stages:
- Egg (fall and winter only)
- Nymph (resemble small adults)
- Adult (may or may not have wings)
Various soybean aphids and nymphs
Management Practices
- Population factors
- Consider using seed treated with a nicotinoid insecticide to delay soybean aphid population establishment, especially in late plantings
- Temperatures in the low to mid 70s promote longevity and reproduction (doubling time is less than two days)
- Allow lady beetles, insidious flower bugs, and other beneficial insects to suppress populations
- Scout fields in July
- Use economic threshold of 250 aphids per plant to justify insecticides
- Insecticide control
- Spray fields before aphids reach 1,000 per plant and plant stage R5.5
- Plant resistance
- Natural antibiosis – Monitor varieties with least antibiosis first
- Natural antixenosis
