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The Birch Leaf Miner: Ninth In A Series Of Articles On Edmonton Tree Care

The Christmas holidays have come and gone, and we reveled in New Year celebrations, and already we are turning the 2016 calendar pages. While winter weather continues to dominate our home care tasks, as we shovel and salt our porches and walk-ways, the experts here at Chipps Tree Care want to remind you that spring is only a scant few months away. Lawn and tree care is all about being proactive, and nipping problems in the figurative and literal bud, and so we want to offer you advice on how to keep pesky insects and pests from damaging your spring foliage growth.

As the ninth and penultimate installment on Alberta Tree Dangers, we turn our attention to the Birch Leaf Miner, one of the most common leaf problems that distress Edmonton-area homeowners.

Birch Leaf Miners are the caterpillar-like larvae of at least 3 or 4 species of tiny sawflies that mine birch leaves. Sawflies are named for the saw-like ovipositor (egg-layer) at the ends of the female’s abdomens. Sawflies overwinter as pupae in the soil beneath a birch tree, and in spring the emerging adults mate and the females fly to birch leaves to lay their eggs. The female sawfly cuts a slit in a birch leaf with her ovipositor and lays an egg inside the leaf, deposit their eggs singly usually near the tips of branches. More than one female may lay eggs in a leaf. The Birch Leaf Miner does this in late May and a second generation follows two weeks later. Other similar species perform their egg laying later in the spring or summer.

The Leaf Miner is a nuisance because the areas of the leaves it consumes turn an unappealing brown color. Because people often do not see the early signs of Birch Lead Miner feeding, it often appears the tree has suddenly dried up or become diseased. This browning is caused by the outer layers of the leaf drying out after the larva has consumed the healthy green tissue between the outer layers of the leaf.

Because early mines appear as light green or whitish discolorations on the leaves, an infestation can be spotted early and treated by trained arborists. Larvae themselves can be seen easily when leaves are held up to sunlight, especially as the mines and larvae grow in size. Feeding over several weeks causes the blemish to take on a blister-like appearance. A single leaf can contain as many as 40 larvae and heavy infestations of larvae can seriously harm a tree’s photosynthetic capacity. Repeated attacks will undoubtedly cause stress which may induce susceptibility to other, more serious injurious agents — which means more disease and infestation might be on the way unless the birch is treated by a certified arborist.

Luckily, there are a number of preventative and curative measures employed by the expert team of specialists at Chipps Tree Care that have helped a number of past customers. If notified in time, our technicians can help prevent and even reverse the effects through a number of measures:

• Chemical sprays are not effective, since the larvae are protected inside the leaf. Cygon, a systemic pesticide that was used in the past as a soil drench is no longer available, and is no longer considered a safe agent.

• A new system of injecting pesticide directly into the stem of the tree has been developed and has shown promise in controlling this insect. These systemic insecticides are chemical pesticides that are absorbed directly into the tissues of plants, rendering the entire plant, or parts of the plant, poisonous to insects that feed on the plant tissue.

• Keep your birch well-watered, as birch need more water than most trees. Birch health is mainly a function of how much water they receive.

Hopefully these tips will help you keep the Alberta Birch Leaf Miner at bay this spring. And remember: if you do spot any discoloration, or suspect the presence of larvae, contact the experts at Chipps Tree Care right away.