Basswood Leaf Miner: Appearance, Territory, Damage and Life Cycle

Latin Name: Balios S Rubber

Appearance: Adults of the basswood leafminer are wedge-shaped and about 1/4″ long; females are somewhat bigger than males. The blotch-like leaf mines initially house a single larva, but when mines merge, they may eventually house multiple larvae. In August, fresh adults emerge from the leaf mines after pupation. The yearly burning of basswoods is caused by leaf eating damage from this fresh crop of adults mixed with larval leaf mining activities.

Hosts Plants: The basswood leafminer is most commonly associated with its namesake plant, although insects may feed and develop on a variety of other hosts, including members of the Tilia genus such as small leaf linden and silver linden.

Territory: North America

Damage Insect Cause: Leaf-miner damage is ugly and, if left handled, can result in catastrophic plant damage. Taking actions to rid plants of leaf miners can not only enhance their appearance but also their general health. Although the insects are classified as leaf skeletonizers, their damage is more correctly defined as scarifying or “surface skeletonizing.” The little adults’ mandibles are too small to eat through the leaf fully; they can only remove the leaf surface. The opposing side of the damage’s epidermis dehydrates and degrades, leaving behind a fine-textured network of skeleton-like leaf veins. This is in contrast to the coarse skeletonizing induced by Japanese beetles, which swallow everything but the bigger leaf veins with their considerably larger mandibles.

Life History and Habits: The locust leafminer (Odontota dorsalis), which can cause black locusts to “flame” in late summer, is linked to the basswood leafminer (Odontota dorsalis). Both belong to the Chrysomelidae family, as well as the Cassidinae subfamily and the Chalepini tribe of leaf beetles. The bulk of this tribe’s beetles have similar life cycles and habits, with adults feeding as leaf skeletonizes and larvae feeding as leafminers.

There is just one generation every season, although adults are present at two separate times during the growth season, like with the locust leafminer. Adults spend the winter under host trees in leaf litter. They appear in the spring to feed on freshly growing leaves as skeletonizes. When observed up close, the damage may be visible; nevertheless, it is seldom severe enough to cause whole trees to change color. Females lay eggs in June, placing solitary eggs behind the top epidermis near the margin of a skeletonized region. As leafminers, the developing grub-like larvae eat between the top and lower epidermis.