Native Holly Leafminer
Egg -The white egg is oval and 0.25 mm long.
Larva -The pale-yellow, legless larva is tapered from front to back, with its head retracted into the body. The larva is 1.5 mm long.
Pupa -The oval pupa is reddish brown, 2 mm long, and uniformly tapered to blunt points at both ends.
Host Plants -The native holly leafminer has infested American, Japanese, Chinese, English, and yaupon hollies. Other hosts include winterberry (or black alder) and inkberry (or bitter gallberry) and their varieties. The fly is particularly damaging to the American hollies.
Damage -It is the most injurious insect pest of holly in the eastern United States. The larval leaf-mining can cause partial defoliation, especially during a dry season; and the mines make the trees unattractive. Moreover, the females insert their ovipositors into the leaf tissue, causing wounds from which sap flows. Both females and males then feed on the sap. This wounding deforms the leaves. The leafminers prefer new growth.
Life History -There are three larval stages in the life cycle of this fly, the last of which overwinters. In March and April the larvae pupate, and adult flies begin to emerge in May. They have a brief lifespan; females live 3 days, males only 2. Eggs are inserted into the undersides of newly formed leaves, causing tiny, green blisters to appear on the leaf bottoms. Most eggs are laid near the tips of the leaves, close to the midveins. Eggs hatch in about 4 days. The larvae mine into the leaves, remaining there for 9 to 10 months. The mines are yellowish brown and usually contain only one larva apiece. Each serpentine mine eventually broadens into a blotch, which contains the pupa. Just before each larva pupates, it prepares a circular exit hole covered by a thin layer of leaf cells.
If only a few plants are damaged, picking the mined leaves and burning them gives some control. For specific chemical controls, see the current state extension service recommendations.