Edmonton Journal

PROTECTING BIRCH TREES FROM BORER WORMS

- GERALD FILIPSKI Growing Things Gerald Filipski is a member of the Garden Writers Associatio­n of America. Email your questions to filipskige­rald@gmail.com He is the author of Just Ask Jerry. To read previous columns, go to edmontonjo­urnal.com/filipski

Q I received the following email from one of the local tree service companies: ‘Do you know of any treatment or prevention options for the birch borer worm?’ While we have addressed this issue in the past it appears it might be time to revisit the problem. We have been unable to help our customers on this issue and are hoping you have some advice for us.

A The bronze birch borer is native to North America, and in Canada is found from Newfoundla­nd to British Columbia. This insect targets old and stressed birch trees. They bore under the bark and feed on the tissue of the tree that conducts sap. The borers start at the top of the tree and work their way down. One of the sure signs of borer infestatio­n is that the top of the tree is completely without leaves. The feeding activity of the borer girdles the branches and trunk of the tree. This girdling eventually will choke off the sap flow completely, causing the death of branches and eventually the tree.

The best way to control birch borer is to maintain the health of your trees, as borers will normally not attack healthy trees. Sufficient water for birches is absolutely critical for their health. Birch are trees that are native to rivers, lakes, and other areas with high water levels. They do very poorly in drought conditions. Over the past few years we have had some very dry conditions. It is in the spring that birch trees need the most water. They can draw up hundreds of gallons of water each day. If there is no water reserve in the soil for them to draw on they will go into stress and become very prone to birch borer attack. Watering the birch during the fall to build up the water reserve is critical to their health.

Turn your garden hose to a gentle trickle and place the hose at the base of the birch tree. Let the water trickle out for at least two hours. If you have a soaker hose this is even better. Turn the hose upside down so the holes are facing the ground and turn the water on to a very gentle flow. This type of watering delivers water deeply and helps to keep the roots from drying out during the winter months.

Unfortunat­ely, once a tree is infested with borers it is impossible to eradicate them. Signs to look for include ridging of the bark. You can actually feel the ridges by running your hand along the trunk and/or branches. Another telltale sign are D-shaped holes in the bark, from which the adults emerge. The holes look just like a typewritte­n D and are of the same size. If a tree exhibits top dieback symptoms then dead branches should be pruned out in the fall 30 to 50 centimetre­s below either the dead wood or any signs of successful beetle attack (the D-shaped holes). All pruned material should be destroyed to prevent any beetle emergence the following spring.

A Thank you for being such a faithful reader. I think the problem with your peonies is you may have planted them too deeply. The top of the roots of the peony should not be planted deeper than five centimetre­s below the surface of the soil. If it is then the plant will not bloom.

Q Your advice on a previous gardening question provided a veritable home run. I’m hoping you can help me with another. Two years ago I planted a couple of peonies (Paeonia Hybrid ‘Modesta’) purchased from a reputable local gardening centre. Neither has yet produced any blooms. The plants are in a sunny spot, against a white fence, have good soil and are fertilized monthly (all-purpose flowering plant fertilizer). The plants themselves are bushy and healthy. But, alas, no blooms to date. So what’s up? Am I doing something wrong or do I just need to be patient for another year (or two, or three)? Thanks for whatever advice you might provide. And keep up the fine work on your Journal gardening column, it’s a weekly ‘must read.’

 ?? LAURA KELSO/EDMONTON JOURNAL ?? Birch borer worms do not normally attack healthy trees, so keeping your birch in good shape is the best way to ward off these pests. Infestatio­ns can be fatal to the tree.
LAURA KELSO/EDMONTON JOURNAL Birch borer worms do not normally attack healthy trees, so keeping your birch in good shape is the best way to ward off these pests. Infestatio­ns can be fatal to the tree.
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