What You Should Know About the Birch Leafminer

One of the bigger pests you have to deal with in summers in the northern United States and Canada is the birch leafminer. The pest’s name comes from its practice of feeding on the plant tissues in between the upper and lower surfaces of birch leaves.

Here’s some information about the pest that you should be aware of, from a company that specializes in pest control in Alaska.

What effects does the leafminer have on birch trees?

You can tell when a birch tree has been affected by the leafminer because the leaves will inexplicably begin to turn brown. From a distance, trees that have been affected by the insect will look blighted or even scorched, to the point where it may look like the tree is diseased. In actuality, the tree is healthy, it’s just that it’s been overwhelmed by the leafminer. Upon closer inspection, you’ll notice that the leaves have blotches, or may appear to be blistered.

Typically, it’ll be the leaves near the tops of the trees that are most heavily affected, though the insect could attack the entire tree. A healthy tree is able to lose part or even almost all of its crop of leaves without being majorly weakened, but if this continually happens year after year, the tree will get weak and die, or become susceptible to attacks from other types of insects that will hasten its death. The bronze birch borer, for example, often comes in for the “scraps” of the leafminer, and it can quickly do some significant damage to a tree.

What do I need to know about the bug itself?

The birch leafminer is an invasive species from Europe. It is small, black, has four wings and is about an eighth of an inch long. They stay in the soil over the winter and start to emerge from their slumber in early to mid-May, congregating around birches. Females will lay their eggs in newly developing terminal leaves on the trees, and those eggs hatch within 10 days.

Larvae start feeding on the birch immediately. At first, the “mines” they create with their feeding are small, but as the larvae get bigger, their feeding increases and those mines start to get larger and more obvious, resulting in the aforementioned blotches and blisters. After about one to two weeks, the larvae mature, go down into the ground to pupate and come back out as new adults two to three weeks later, at which point the cycle begins again. You can expect three or four generations of these bugs to appear each year, though it’s the first two generations that cause the most damage, because the leaves are still soft and new for them.

How do I control their population?

There are sprays available on the market that are specifically designed to combat the birch leafminer. It is important to spray at the proper time, just after the eggs hatch. This means spraying around Mother’s Day and the Fourth of July if you’re going to get the first and second generation right as they come out.

You should carefully examine new leaves when they start to form, and if you can see mines when you hold the leaves up to the light, you know it’s time to spray.

For more information about the birch leafminer, or to get professional assistance with insect control in Alaska, contact the team at Pied Piper Pest Control today.

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