**Leafroller Caterpillars** is a general term referring to the larvae of several species of small moths (family Tortricidae, often called Tortricid Moths). These caterpillars are distinguished by their behavior of using silk to **roll, fold, or tie together** host plant leaves to create a protected shelter for feeding. They are significant, polyphagous pests of fruit trees (apples, peaches), berries, ornamental shrubs, and many agricultural crops. The damage includes defoliation, destruction of developing buds, and direct feeding damage on the surface of developing fruit, which drastically reduces crop marketability.
Taxonomy and Classification
Leafroller Caterpillars belong to the order Lepidoptera. They undergo complete metamorphosis. Common examples include the Obliquebanded Leafroller (*Choristoneura rosaceana*). The caterpillar is known for its high mobility and its tendency to drop from the rolled leaf on a silken thread when disturbed. The adult moths are typically small, brownish, and cryptic.
Physical Description
Leafroller caterpillars are 1/2 to 1 inch long when mature.
- **Larva (Key ID):** Small, smooth, green or pale yellow caterpillars with a distinct, often dark brown or black head capsule. When disturbed in their rolled-up shelter, they will wriggle violently and often drop on a silk strand.
- **Shelter (Key ID):** Leaves are rolled up, folded, or tightly tied together with white silk strands. The caterpillar feeds safely inside this structure.
- **Damage Sign:**
- Defoliation of the terminal (new) growth.
- **Fruit Damage:** Scraped patches, scarring, or deep feeding cavities on the surface of developing fruit, rendering it unsalable.
Distribution and Habitat
Leafroller Caterpillars are found globally wherever their host plants (especially woody plants) are grown. Their habitat is the foliage and terminal growth of fruit trees, vines, and ornamental shrubs.
Behavior and Conflict
The conflict is significant economic damage to fruit and ornamental crops.
- **Fruit Scarring:** Their feeding on young fruit causes scars that expand as the fruit grows, resulting in culls at harvest time.
- **Protected Feeding:** The silk shelter physically protects the caterpillar from predators and from many contact insecticides, making control difficult.
- **Multiple Generations:** Many species have multiple generations per year, leading to prolonged pest pressure from spring through harvest.
Management and Prevention
Control is integrated pest management (IPM), with a heavy focus on monitoring and targeting the young larvae.
- Use **pheromone traps** to monitor the flight period of the adult male moths, which helps precisely time the insecticide application to the vulnerable, newly hatched larval stage.
- Apply **Bacillus thuringiensis (Bt)**, a bacterial insecticide specific to caterpillars, when young larvae are active. Bt must be ingested and is non-toxic to beneficial insects.
- Manually crush or prune out rolled leaves to destroy the larva inside.
- Apply insecticides targeting the small, newly hatched larvae before they create their protective leaf rolls.
Conservation and Research
Leafroller Caterpillars are managed as major fruit pests. Research focuses on implementing **mating disruption** techniques (releasing large amounts of synthetic pheromone to confuse males), optimizing the timing of biological control agents, and developing better monitoring systems.