Mulberry leafrollers are caterpillar pests that feed on the leaves of mulberry and other host plants. They are named for their behavior of rolling leaves into protective shelters, where they feed and develop.
While individual infestations may seem minor, large populations can lead to significant defoliation and reduced plant health, particularly in ornamental or fruit-producing trees.
The Silk-Spun Suite: Mulberry Leafrollers
The Mulberry Leafroller (primarily Glyphodes pyloalis) is a specialized moth pest that targets both ornamental and fruit-bearing Mulberry trees. While native to Asia, it has established itself in several regions of the United States. As the name suggests, the larvae are architectural pests, using high-tensile silk to physically roll or fold leaves into protective tubes where they feed in relative safety from birds and parasitic wasps.
The “Envelope” Feeding Strategy
The damage caused by the Mulberry Leafroller is highly structural. Unlike general defoliators that eat the entire leaf, these caterpillars create a controlled environment for their development:
- Leaf Folding: Young larvae spin silk threads that shrink as they dry, pulling the edges of the mulberry leaf together to form a tight roll or “envelope.”
- Skeletonizing: Inside this roll, the larvae graze on the tender green tissue (parenchyma), leaving behind the veins and the outer “skin” of the leaf. This results in brown, papery patches that are visible from the outside.
- Frass Shelters: The interior of the roll often becomes cluttered with dark frass and cast-off skins, which can promote the growth of localized mold if humidity is high.
Identification and Rapid Turnover
The adult moth is distinctive, featuring translucent white wings with intricate brown wavy lines and borders. In the warmer parts of the U.S., the Mulberry Leafroller can complete a full life cycle in as little as 30 days, leading to multiple generations between late spring and the first frost. This rapid turnover allows populations to explode unnoticed until the entire canopy appears “tattered” or scorched.
U.S. Management and Control
Because the larvae are physically shielded inside their silken rolls, contact insecticides often fail to reach them. Effective management requires a more targeted approach:
- Manual Removal: For small landscape trees, simply pinching or removing the rolled leaves in early summer can significantly reduce the second and third generations.
- Bacillus thuringiensis (Bt): This organic biological control is highly effective if applied when the larvae are young and still moving between leaves to start new rolls.
- Winter Sanitation: The final generation of the year often pupates in the leaf litter beneath the tree. Raking and composting (or destroying) fallen mulberry leaves in autumn is the best way to prevent a spring outbreak.
Identification
Larvae are small green or brown caterpillars often found inside rolled leaves. Adults are small moths that are rarely noticed.
Life Cycle
Eggs are laid on leaf surfaces. Larvae hatch and begin feeding, rolling leaves as they grow. Pupation occurs within the rolled leaf or nearby debris.
Damage
Damage includes leaf rolling, skeletonization, and reduced photosynthesis. Heavy infestations can weaken trees over time.
Control
Control methods include pruning infested leaves, applying biological insecticides such as Bacillus thuringiensis (Bt), and encouraging natural predators.