**Sawflies** (Order Hymenoptera, suborder Symphyta) are the larvae of non-stinging wasps, and they are significant pests of trees, shrubs, and field crops. Common landscape pests include the **Pine Sawfly** (*Neodiprion* species) and the **Rose Sawfly** (*Endelomyia aethiops*). The conflict is severe to aesthetic **defoliation**: the larvae feed gregariously, consuming foliage and causing rapid, visible leaf damage, leading to plant stress, reduced growth, and loss of ornamental value.
Taxonomy and Classification
Sawflies belong to the order Hymenoptera. They undergo complete metamorphosis. The adult female uses a saw-like ovipositor (egg-layer) to slice into plant tissue (hence the name) and deposit eggs. The larvae are often mistaken for caterpillars but have six or more pairs of prolegs (fleshy legs) on their abdomen, while true caterpillars have five or fewer.
Physical Description
The destructive larvae are 1/2 to 1 inch long.
- **Larva (Key ID):** Slug-like, smooth, or spiny, often brightly colored, and usually found feeding in dense, exposed clusters (e.g., Pine Sawflies) or singly (e.g., Rose Sawfly, which is slug-like).
- **Movement:** When threatened, some species rear up their bodies in a defensive posture.
- **Damage Sign (Key ID):**
- **Skeletonization:** Larvae chew out the soft tissue, leaving the leaf veins intact (e.g., Rose Sawfly).
- **Needle Loss:** Pine Sawflies consume entire bundles of pine needles, leaving the branch bare except for the central stem.
- **Conflict:** Rapid defoliation and plant stress.
Distribution and Habitat
Sawflies are found globally. Their habitat is the foliage of their specific host plant (e.g., pine, oak, rose, willow). Many species are host-specific, meaning they will only feed on one or two plant genera.
Behavior and Conflict
The conflict is defined by the severity of their group feeding.
- **Group Feeding:** Many sawfly species feed gregariously, consuming all the needles or leaves on a small branch before moving as a group, leading to rapid, noticeable damage.
- **Chemical Resistance:** Sawfly larvae are **not** affected by *Bacillus thuringiensis* (Bt), the common biological control for moth caterpillars, requiring different control strategies.
- **Stress:** Repeated defoliation can severely stress trees and, in the case of evergreens, lead to dieback or death.
Management and Prevention
Control is integrated pest management (IPM), favoring mechanical and targeted contact sprays.
- Because they feed in clusters, large groups can often be controlled by simply **pruning off the infested branch** or scraping the cluster of larvae into a container of soapy water.
- **Horticultural Soap/Oil:** Apply insecticidal soap or a light horticultural oil to contact the larvae directly.
- **Targeted Insecticides:** Use a residual insecticide labeled for sawfly control. Application must be timed to target the young, newly hatched larvae.
Conservation and Research
Sawflies are managed as landscape and forestry pests. Research focuses on their population cycles, the development of natural enemy programs (especially parasitic wasps and flies), and improving host plant resistance.