By Christine Freeburn, Master Gardener

As gardeners, we are aware of the importance of trees. In our yards they give us shade from the hot sun, dropping the temperature beneath them and cooling the air. They give habitat to birds and insects. They purify the air and help reduce greenhouse gases. They anchor the soil and
help with soil erosion. They give us privacy. Studies have shown that trees also help our mental health. In the past few years, ice storms, spongy moths, wind storms, and the recent derecho have damaged many trees in our area. Around every neighbourhood, you hear the buzz of chainsaws throughout the year. Last week, we had one of our lovely big sugar maples cut down because it became diseased. Heartbreaking but necessary to have it taken down.

Fungal diseases are often the culprit of the decline and death of many species of trees. Trees that are planted where their roots have no good earth to grow in become stressed. A stressed plant is easier for pests and diseases to invade. Our sugar maple was close to our driveway and although it is not paved, the ground is compacted.

Years of drought also affect a tree’s health. Wind storms can damage branches and leave open wounds where disease can find its way in. We are all familiar with Dutch Elm disease which has been in Ontario since 1946. It is a highly contagious fungal disease that has almost wiped out elm trees. Many of the dead trees you see along roadsides are elms.

Anthracnose is a common disease in maple and oak trees. It often appears after a damp cool spring. Brown blotches appear on leaves, they dry up and fall off. When combating this disease, you need to rake up and dispose of infected leaves. Tar Spot is common on norway maples. Although it may not kill your tree, it is a fungal disease and will continue to spread. It is recommended to rake up leaves and dispose of them rather than mulching them.

Spruce trees were stressed by the spongy moths and drought and we are seeing them suffering with Cytospora Canker. Signs of this disease are needles turning purple, then brown, then dropping off leaving branches bare but covered with a white resin. Cankers appear on the branches near the trunk.

Last week’s post was on Oak Wilt, a recent fungal disease which has no chemical control yet. Pests are also a huge problem with our trees. Emerald Ash Borer has been in Ontario since 2002. The metallic green beetle emerges in late June, laying eggs in crevices of bark. Larvae overwinter under bark and tunnel under the bark leaving “S” shaped marks which cuts off the trees ability to draw food and water. There is an insecticide that a professional can inject into the tree.

Spruce budworm is native to North America. It attacks balsam fir (Abies balsamea), white and black spruce (Picea), hemlock (Tsuga), jack and eastern white pine (Pinus) and Larch (Larix). BTK has been used to control, however if you have a mature tree this option is overwhelming. We all need to be aware of the health of the mature trees on our property. Ensure they are getting enough water, watch for small leaves or broken branches and pest infestations. Call an expert arborist to give advice on an ailing trees. They can also help with any pruning issues that might need to be addressed.

If you are investing in a tree for your property, be sure to do some research and find the right tree for the right spot. Take into consideration how big the tree will get, where the sun will shine on it, how much ground it will have to absorb moisture and what competition it might have. Young trees need lots of water to get established and grow. What’s that old saying? Hug a tree? Well, after you hug your tree, check out the references below for more information on diseases and pests and ways to help your trees.

References

https://www.toronto.ca/services-payments/water-environment/trees/forest-management/threats-to-trees-diseases/
https://www.ontario.ca/page/dutch-elm-disease
https://extension.umn.edu/plant-diseases/cytospora-canker
https://www.canr.msu.edu/news/black_polka_dots_on_maple_tar_spot