GBA Update Summer 2024

LAND & FORESTS

By Richard Wilson, Chair, Land & Forests Committee

Bad Things Might Come in Threes to Trees

I nvasive species continuously threaten our forest ecosystem. We recently discovered three new species in Southern Ontario that could harm the ecosystem. We need your help identifying and monitoring these species and preventing potential damage. Protecting our ecosystem is our responsibility, and we can only do that by working together.

Oak Wilt

Hemlock Woolly Adelgid

What Is It? Oak wilt is a vascular disease caused by the fungus Bretziella fagacearum and affects mainly red oak and sometimes white oak. The fungus grows on the outer sapwood of the tree and restricts vascular flow. Trees that are infected with this disease can perish within six weeks. Three occurrences were detected in Ontario in 2023: two in the Niagara region and one in Springwater Township. How to Spot It? The first signs of the disease are the leaves turning brown or yellow prematurely, with the discolouration moving from the edge of the leaves towards the centre and from the top of the tree downward. This leads to premature leaf fall. Eventually, fungal mats grow under the bark and cause large vertical splits in the tree bark. At this stage, the tree is dead. What Can You Do? Several vectors spread fungal spores and are very hard to control. Once a tree is infected, there is no cure. Avoid pruning oak trees from April to July. If a tree does have a break or cut, seal it with wound paint. Do not move firewood over a distance, particularly if the tree shows signs of disease. Report suspected or confirmed outbreaks to the Canadian Food Inspection Agency (CFIA) as outlined below.

What Is it? Hemlock woolly adelgid (HWA) is an invasive, aphid-like insect. It was first detected in Virginia in the early 1900s and has now spread through most of the eastern USA and into southwestern Nova Scotia. It affects eastern hemlock, a foundation species for many forests at east Georgian Bay. In 2023, trees harbouring this insect were found in Haldimand County and the Niagara Region. The hemlock woolly adelgid insect feeds on the nutrients and sap at the base of hemlock tree needles, leading to the death of the affected tree in four to fifteen years. HWA can be controlled by various chemical treatments, as well as through forest management and biological controls. How to Spot It? The telltale sign of this pest is the white woolly egg sacs. They are permanently attached to the twig at the base of the needles and can be seen from November to May. The occurrence can be high in the tree, so check branches on the ground after spring storms. Trees beside lakes or in areas frequented by birds and animals (which can carry the nymphs) are the most prone to infection. What Can You Do? Keep your trees healthy by not wounding them and watering them during dry spells. Healthy trees are resilient trees. Don’t hang bird feeders in hemlock trees, and monitor for egg sacs, particularly in early spring. Tree care professionals can treat egg sacs, but CFIA would still like you to report it.

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GBA UPDATE Summer 2024

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