Symptoms: These critters cause translucent, see threw trails, blisters and blotches on leaves that eventually turn brown. Often, you can see tiny, dark specks inside the trails that rattle around when you shake the leaf. If you open a leaf and look into the trails, you might find tiny green, yellowish or whitish larvae. Certain species such as elms (Ulmus), columbine (Aquilegia) and birch (Betula) are routinely damaged by leaf miners.

More on birch leaf miner, columbine leaf miner, elm leaf miner.

Diagnosis: Leaf miners are the larvae of species of flies, beetles or sawflies.  The adult comes around as soon as the leaves fully expand and lay their eggs. The resulting larvae feed between the upper and lower surfaces of the leaves causing the translucent trails. After feeding for a specific period of time, they either eat through the leaf and drop to the ground to mature or they mature inside the leaf, eat their way out and fly away.

Some of the species such as the birch leaf miner have more than one generation per growing season.

Treatment: Since they spend most of their lives inside the plant leaf, contact insecticides normally do not work well on these pests. So, the more standard treatment is to use systemic insecticides that either penetrate into the leaf or go from the roots through the system of the plant.

You need to know the life cycle of the particular type of leaf miner in order to determine the best time for treatment. Systemic products take time to move through the system of the plant.

Check with your local Extension Service for current recommendations for control of your particular type of leaf miner.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.


Types of Insects

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