GardenLine | Common Saskatchewan Pests | The Birch Leaf Miner

The first sign of a birch leaf miner infestation is that the centre of the leaves appear to be a lighter green than on the edges. As the leaf miner continues to eat, brown spots near the centre of the leaf become apparent. The leaf miner will continue to feed on the inner leaf tissue. The results of which resemble blisters and have many small black specks of frass (waste) distributed throughout the damaged tissue. Damage is usually apparent in June.

Control

The most common method used for controlling the birch leaf miner is a soil drench using undiluted dimethoate (sold as Cygon and Lygon). Several small holes should be made in the soil directly under the branches. The dimethoate is then poured into the holes in equal quantities. The total amount to be used will depend on the trunk diameter of the tree measured at 4.5 feet above the ground. In a multi-trunked tree the cumulative total diameters is used. Remember to read the product label directions very carefully to determine the correct amount. Never add more chemical than is recommended. Only one soil drench per year is required to control the miner and is applied in early to mid May while the tree is leafing out. Cygon 2E (23.4% emulsifiable concentrate) is applied at a rate of 50 mL for each 2.5 cm (4 Tbsp or 2 fl oz per in.) of tree trunk diameter. READ LABEL DIRECTIONS!

The soil drench method is the preferred method of application as foliar spraying and drift are avoided and the leaf miner is controlled before any damage can occur. The soil drench is considered to be the most effective application method but, if for some reason, the soil drench is inappropriate, the label does include directions for spraying or bark painting (however this method is NOT recommended).

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Sustainable horticultural information, offered free of charge to the public with the support of the University of Saskatchewan Extension Division, the Department of Plant Sciences and the Provincial Government.