**Garden Centipedes** is a general common name often used for the **Symphylan** (*Scutigerella immaculata*), also known as the **Garden Symphylan** or **Symphylid**. Despite the name, these are not true centipedes but soil-dwelling myriapods that are notorious pests in greenhouses and outdoor vegetable and flower gardens. They feed aggressively on tender root hairs and root tips, causing wilting, stunting, and death in seedlings and young plants, especially in cool, moist, organic-rich soils.
Taxonomy and Classification
Garden Symphylans belong to the class Symphyla, which is distinct from centipedes (Chilopoda) and millipedes (Diplopoda). They undergo simple development, continuing to molt throughout their life. They are characterized by being small, soft-bodied, and having 12 pairs of legs as adults, though they only have six pairs when newly hatched.
Physical Description
Garden Symphylans are tiny, measuring only $1/16$ to $1/4$ inch long.
- **Appearance:** Soft, white, translucent, slender bodies that resemble tiny centipedes. They have long, multi-segmented antennae.
- **Movement:** They are extremely fast-moving and quickly escape into the soil when disturbed, making them hard to observe.
- **Damage Sign:** Symptoms are non-specific and mimic disease: poor stand establishment, yellowing, stunting, and wilting. Inspection of damaged roots reveals fine, reddish-brown scar tissue on the root tips, and the root structure may be entirely missing its fine feeder roots.
Distribution and Habitat
Garden Symphylans are cosmopolitan. Their habitat is the top $6$ to $8$ inches of soil, particularly in fields, gardens, and greenhouses with high organic matter, good moisture, and cool temperatures. They move vertically in the soil profile, moving deeper to escape dry or cold conditions and moving to the surface to feed on roots.
Behavior and Damage
Symphylans can live for several years, reproducing continuously in protected environments. They cause damage by feeding on the delicate root tissues of seedlings and young plants.
- **Root Damage:** The continuous pruning and destruction of root hairs prevent the plant from establishing a healthy root system, leading to the failure of young plants.
- **Broad Host Range:** They feed on nearly all vegetable and flower crops, making crop rotation an ineffective management strategy.
- **Feeding Preference:** They prefer the fine, tender root tissues of young plants but will also feed on fungal mycelia and decaying organic matter.
Management and Prevention
Control is difficult due to the symphylan’s subterranean lifestyle and high mobility.
- **Cultural Control:** Allow the soil to dry out and warm up before planting, as this discourages their activity. In fields, **deep tilling** (plowing) can disrupt their habitat and kill many individuals.
- **Trap Cropping/Monitoring:** Place slices of potato or apple just below the soil surface to attract symphylans for monitoring population levels.
- **Fertilization/Vigor:** Applying fertilizer to encourage rapid, vigorous root growth allows plants to outgrow the damage before it becomes lethal.
- **Chemical Control:** Control typically requires pre-plant soil fumigation or the incorporation of granular soil insecticides into the top few inches of the soil, which is often limited to commercial operations.
Conservation and Research
Garden Symphylans are managed as serious soil pests. Research focuses on developing effective biological controls (such as parasitic nematodes) and improving methods for heat sterilization and non-chemical treatment of greenhouse and container soil.