Question
My white birch is about 12 years old and is covered with leaves that have tiny pin holes (eaten to lacy effect), turn brown and fall off.  I saw a prior posting regarding the birch leafminer, but they were described as being a black flying insects.  Mine are are tiny (less than 1/8"), translucent white with green tinge, with 6 legs.  I'm not sure if they have 2 or 4 wings.  I live in SE Wisconsin.  We had a very wet spring, but now dry.

Thanks!

Answer
Sounds like birch leafminer.
Damage to birch trees is done by the larval stage as it feeds between the upper and lower layers of the leaves. This feeding produces large blotch mines in the leaves. Often, several larvae will completely mine a single leaf. Multiple generations and high populations can cause damage to almost every leaf by mid-summer. The mines turn brown and will cause the tree to look dead with wilted brown leaves. This forces the tree to refoliate and reduces its ability to produce food for growth. This damage may also make the trees more susceptible to bronze birch borer attack. Though the adult birch leafminers are related to wasps, they do not have a sting.

Mature larvae overwinter in the soil under host trees. When the soil warms in the spring these prepupae pupate, usually in April, to transform into the adult stage. Within a few weeks the adult sawflies dig out from their earthen cells and fly to the newly expanding foliage of birches. The small black adults prefer to mate and oviposit on the upper leaves, especially in sunny areas. Mated females use their needle-like ovipositor to punch a hole in the leaf and lay eggs. Often the female withdraws the ovipositor without laying an egg. The damaged spot may turn brown as the leaf expands and hardens. The eggs are often visible in the tissues between the major leaf veins. They may appear as small raised spots on the leaf surface. Within 7 to 10 days the eggs hatch into tiny flattened larvae with wide front segments. These larvae produce a blotch mine that may join with others. The old mines may contain considerable amounts of dark fecal pellets. The larvae mature in 14 to 20 days and are about 1/4 inch long. By this time the larva have the diagnostic small black square marks on their lower surface. Mature larvae cut a hole in the leaf epidermis and drop to the ground. Here they dig one to two inches into the soil to form a pupation chamber. Birch leafminers usually produce two to three generations a summer.

Systemic insecticides, especially easily translocated materials, can be applied to the foliage,or by soil injection. Attempt to control the first generation of larvae when the mines or eggs are first apparent. A systemic insecticide registered for control by spraying the foliage is: acephate (Orthene). A new insecticide that os applied to the soil is called Bayer Advanced Tree and Shrub insect control. The roots transport the insecticide to the foliage killing the insect. Check with your local nursery.garden type store for these insecticides.