BIRCH LEAFMINER
DESCRIPTION
The Birch Leafminer is a serious pest of Gray Birch,
Paper Birch and White Birch in Pennsylvania. It may
occasionally attack 
Black,
Yellow, or even River Birch. The emergence of this pest
in the Spring may initially be recognized by the presence
of the adult black wasps approximately one-eighth inch in
length on newly opening leaves. Larvae may reach
one-fourth of an inch in length and feed in
yellowish-brown blotch mines. There are two generations
per year. Mature larvae overwinter in soil under trees.
LIFE CYCLE
The Birch Leafminer adult is a small, black sawfly with a
wingspread of approximately one-fourth of an inch. In
early Spring, adults emerge and start to lay eggs. Eggs
are inserted singly inside the soft, newly expanding
leaves. After 7-10 days, the eggs hatch into small,
whitish, slightly flattened larvae which feed for 2-3
weeks between the upper and lower leaf surfaces. The
larvae and black fecal matter are easily seen in the
mines when infested leaves are held up to the light. Two
generations of Leafminers are common in Pennsylvania.
Adults of the second generation usually emerge during the
latter part of June.
DAMAGE
Larvae consume the tissue between upper and lower leaf
surfaces. Injury appears in the late Spring as irregular
brown "scorched" areas on the leaf surface. At
first the mines are separate and small, but eventually
they overlap to form large blotched or blistered areas.
Some Birch trees are almost completely browned from top
to bottom because of the feeding activity of this insect.
The tops of the trees are normally the most seriously
affected.
CONTROL
Use a systemic pesticide to kill larvae in newly
developing mines. If the first generation is controlled,
damage for that season is greatly reduced. Effective
control is dependent on timing that can best be
determined by careful observation of the tree foliage.
Thoroughness of the spray coverage is also of equal
importance. Formulations of acephate (Orthene) and
dimethoate (Cygon), are labeled for Birch Leafminer
control.* Insecticides should be applied in May when the
leaves are fully extended. Repeat in mid-late June.
Follow all label directions for specific information on
host plant label clearance, phytotoxicity information,
safety precautions and dosage information.
* See Woody Ornamental Insect, Mite and Disease Management, The Pennsylvania State University (2005) for more details.
WARNING: Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of reach of children, pets and livestock. Dispose of empty containers right away , in a safe manner and place. Do not contaminate forage, streams or ponds.
For professional assistance
with tree and shrub problems,
contact Keystone Tree Experts at (215) 348-4444.
