**Lupine Aphids** (*Macrosiphum albifrons*) are very large, distinctive aphids that feed exclusively on plants in the genus **Lupinus** (Lupines). They are considered a significant ornamental and ecological pest because they aggregate in massive numbers on the stems and flower spikes, causing severe stunting, stem deformation, and significant aesthetic damage. They are also highly efficient vectors of plant viruses that affect ornamental and cultivated lupine varieties.
Taxonomy and Classification
Lupine Aphids belong to the order Hemiptera (true bugs). They undergo incomplete metamorphosis and reproduce asexually (parthenogenesis) for most of the year, leading to explosive population growth. They are one of the largest aphid species and possess a striking appearance that makes them easy to identify on their host plant.
Physical Description
Adult Lupine Aphids are quite large for an aphid, 1/8 to 1/4 inch long.
- **Appearance (Key ID):** Pale green to grayish-green body, often covered in a light, powdery wax, and strikingly long, dark antennae and cornicles (tailpipes). They are often found in immense clusters, completely coating the entire flower stem.
- **Honeydew:** They excrete large amounts of sticky, sugary liquid called honeydew.
- **Damage Sign:** Twisted, stunted, and deformed terminal growth and flower spikes. Black **sooty mold** grows on the honeydew, turning the plant black. High viral transmission rates.
Distribution and Habitat
Lupine Aphids are widespread globally wherever native and ornamental Lupines are grown. Their habitat is specifically the stems, leaves, and flower spikes of Lupinus species, often favoring the soft, new growth near the top of the plant.
Behavior and Conflict
The conflict is severe aesthetic damage and disease transmission.
- **High Density Feeding:** Their massive populations quickly drain sap, causing the flower spikes to abort or become severely distorted.
- **Virus Vectors:** They transmit viruses quickly throughout a lupine bed, reducing plant longevity and vigor.
- **Honeydew Nuisance:** The copious amounts of honeydew attract ants and promote the growth of unsightly sooty mold.
Management and Prevention
Control is integrated pest management (IPM), targeting the dense clusters early.
- **Cultural Control:**
- **Physical Removal (Key):** For light infestations, wipe or wash the clusters of aphids off the plant with a strong stream of water or a gloved hand.
- Prune out severely infested spikes and dispose of them carefully.
- **Biological Control:**
- Encourage natural predators like Ladybugs and Lacewings. Lupine Aphids’ large size and aggregation behavior make them easy targets for predators.
- **Chemical Control:**
- Apply insecticidal soap or horticultural oil, ensuring complete coverage of the dense clusters. This must be repeated often due to their high reproductive rate.
- Systemic insecticides are effective but should be used with caution, especially near blooming plants to protect pollinators.
Conservation and Research
Lupine Aphids are managed as high-priority ornamental pests. Research focuses on breeding disease-resistant lupine varieties and studying the impact of the aphids on native lupine populations.