Morning glory leafminers are small insect larvae that feed between the layers of leaves, creating visible tunnels known as mines. These pests commonly affect ornamental plants and vines, including morning glories.
While typically not fatal, heavy infestations can reduce plant vigor and aesthetic appeal.
The Artistic Tunneler: Morning Glory Leafminers
The Morning Glory Leafminer (Bedellia somnulentella) is a small moth whose larvae specialize in “mining” the interior of leaves belonging to the Convolvulaceae family. While they are a common sight on wild morning glories across the United States, they frequently jump to garden favorites like Sweet Potato vines and ornamental Moonflowers, leaving behind a trail of white, parchment-like damage.
The Signature “Serpentine” Mine
Unlike borers that target stems, leafminers live and feed in the narrow space between the upper and lower epidermis of the leaf. Their damage is highly diagnostic and progresses through two distinct phases:
- The Linear Phase: Young larvae begin by chewing a tiny, winding “snake-like” track. As the larva grows, the track widens, creating a silver or white line that maps its feeding path.
- The Blotch Phase: As the caterpillar matures, it shifts from linear tunneling to “blotch” mining, creating large, irregular transparent patches where the green chlorophyll has been entirely consumed.
- Frass Accumulation: If you hold a damaged leaf up to the light, you can often see a dark line of frass (feces) trailing behind the larva inside the mine.
Identification and Rapid Lifecycle
The adult moth is tiny, grayish-brown, and largely nocturnal. The larvae are pale green or yellowish and are remarkably mobile for leafminers; if a leaf becomes too damaged, they can exit their current mine and crawl to a fresh leaf to begin a new one. In the southern U.S., they can produce several generations per year, with populations peaking in late summer and early fall.
U.S. Garden Management
While leafminer damage is visually striking, it rarely kills a healthy, established vine. However, it can significantly reduce the “curb appeal” of ornamental sweet potato vines. Management strategies in the U.S. include:
- Hand-Picking: For small infestations, simply pinching the leaf at the site of the active mine (the widest part) will kill the larva without further damaging the plant.
- Sanitation: Remove and destroy heavily infested leaves and fallen debris in the fall to prevent the pupae from overwintering in the soil or leaf litter.
- Neem Oil: Applications of Neem oil can act as a repellent for egg-laying adults and may penetrate the leaf surface slightly to disrupt the feeding of young larvae.
Identification
Leaf mines appear as winding, white or translucent trails on leaves. The larvae themselves are small and difficult to see.
Life Cycle
Eggs are laid on leaf surfaces. Larvae tunnel within leaves before pupating in soil or plant debris.
Damage
Damage includes reduced photosynthesis and unsightly foliage.
Control
Removing affected leaves, using sticky traps, and encouraging natural predators are effective control methods.