A tree damaged from frieblight disease. Photo Credit: City of Grande Prairie.

By Shane Clausing

fireblight and elm aphids disease

City advising residents to inspect trees for fireblight disease and elm aphids

Jul 31, 2020 | 5:30 AM

The City is advising Grande Prairie residents to inspect the trees in their yards to see if they’ve been infected with fireblight disease or elm aphids.

“Fireblight is a bacterial disease that’s a native bacterial that’s just kind of all over the place, but it needs certain conditions in the weather to actually grow,” explains Integrated Pest Management Technician Ian Hof. “It needs a lot of moisture, some heat and lots of humidity.”

“Last year was the worst outbreak that Grande Prairie’s ever seen, almost every apple tree had it. So, this year is wet as well, but it’s not as wet and as humid, but the fireblight is still around and it’s starting to generate a little bit of momentum. We just want people to be aware of it.”

Hof says that fireblight disease is one of the most harmful for your tree.

“Every species of tree has a different resistance to the bacteria. Some species of trees have basically no resistance and last year those ones died. If you do nothing and don’t put it out then it just sits there and waits the whole wintertime, and if next year is conducive to growing, you’re going to have that much more fireblight in your tree and it’s going to explode.”

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Hof adds that some trees can fight off the disease if they have good resistance.

Some symptoms of fireblight disease include sudden flagging and death of growth, often black/brown and curled or sunken cankers spreading down shoots and branches in front of dying leaves.

Meanwhile, elm aphids are also busy on trees this year. It doesn’t pose a risk to the health of the tree, but it can be annoying for people to deal with.

“The aphid is a little tiny insect that is very soft-bodied, they’re very host-specific so they like one certain thing like a spruce or pine tree,” says Hof.

“Elm aphid is really going crazy this year, it’s a big outbreak. The worst thing about the aphid is that its waste is a strange, harmless, sticky, sugary solution. It drops from the trees and covers people’s property and it’s a mess.”

Elm aphids. Photo Credit: City of Grande Prairie.

Aphid waste can cover the ground and anything else below them in a layer of sticky honeydew.

Honeydew from elm aphids. Photo Credit: City of Grande Prairie.

There are ways to help prevent the spread of fireblight disease and elm aphids.

Those with fireblight infected trees are told to prune out all infected branches 12-18 inches below the infection.

Pruning tools should also be disinfected between each cut with gas line antifreeze or a 10% bleach solution to prevent spreading the disease further throughout the tree.

When it comes to combating fireblight, the City says it handles and controls the trees that are fighting the disease.

“We’ll take care of all of the city trees to stop the spread, but the spread mostly comes from private trees and people that don’t know or care that they have it, and it can spread very easily from there.”

The City also takes control of tackling trees with elm aphids, which experts say are easy to get rid of.

The city says that the best way to do that is by using a pressure washer and shooting the canopy of the elm tree every week to knock the aphids off and drown them. The tree will also benefit from the extra water to replace what aphids take.

Hof mentioned that starting on July 31, the City of Grande Prairie will begin pressure washing it’s city-owned elm trees to hopefully get rid of some of the mess on some Grande Prairie streets.