Stop fungi, viruses and pests in autumn

In late spring, summer and early fall, deciduous trees and shrubs are covered in leaves. During this time, yellow leaves, dead leaves and dead branches are tell-tale signs that the plant is not healthy.

In late spring, summer and early fall, deciduous trees and shrubs are covered in leaves.

During this time, yellow leaves, dead leaves and dead branches are tell-tale signs that the plant is not healthy.

Once the leaves have fallen, it is easier to see irregularities on the branches and trunk.

Any plant can become susceptible to: insects, fungi, viruses or other pest, but most often the plant attacked is not in optimum health.

Plants that have ideal climatic conditions: soil, moisture levels, sunlight, temperature and available nutrients are more likely to resist pests than ones that are stressed.

Paying attention to the plants helps to catch infestations early making, it easier to eliminate them.

Wet springs provide the ideal climate for the black knot fungus to multiply and form rough black lumps on branches of may day and Schubert chokecherry trees.

If the fungus is allowed to grow, it will cut off all the nutrients to the end of the branch.

Removing the problem is as simple as cutting the branch six to eight inches (15 to 20 cm) below the infection area. All infected material should either be burned or double bagged and sent to the landfill.

Urban areas that have used these trees for boulevard trees have hired extra arborists to try to eliminate the problem.

Cankers are harder to spot. Look for areas of bark that are shrunken, leaving a shallow depression.

Cankers tend to plug the plants’ vascular systems, stopping the flow of nutrients past the diseased area, resulting in dead branches or crowns of trees.

As with the black knot, cut out the diseased area and dispose of the infected material.

Wood peckers called yellow bellied sapsuckers drill quarter-inch holes, row after row on trunks or limbs of trees.

Once the holes are drilled, the birds come back regularly to feed on the sap. Loss of sap eventually weakens the tree, causing part or all of it to die.

There is little that can be done to protect the tree as placing a barrier between the tree and bird is virtually impossible without climbing the tree.

Leaving the injured tree as is often keeps the birds using that tree as opposed to starting on a new one.

The birds can not be poisoned or destroyed as they are protected by the Migratory Birds Convention Act.

Slim-flux is prevalent in many poplars. The bacteria increases the pressure of the sap within the tree until it begins to ooze out of cuts, cracks and abrasions.

Trees will live for many years with slim-flux, with the sap oozing from the tree.

Black streaks on the tree and sticky residue under the tree are signs that the bacteria is present.

Small holes with sawdust below are telltale signs that the poplar or willow bore is present.

The larva tunnels its way through the tree, disrupting the plant’s vascular system (the branches food supply).

The only cure is to remove the tree to prevent the insect from spreading to other plants.

Spruce budworm has always been part of the Alberta coniferous forests. The worms are visible the late part of May until early June at the tips of spruce trees, eating the new needles. Spraying the caterpillars with bacillus thuringiensis var kurtaki is an organic solution to the problem.

The caterpillars will eat the sprayed vegetation, develop a bacterial infection in the stomach and die.

If left unchecked, the worms will eat the new needles and spin casings in old and new needles, causing them to turn brown.

The result is a dead brown area on the spruce tree becoming visible in July.

Fire blight attacks fruit trees. Bark of diseased areas turn black, looking as if it went through a fire. Leaves on infected areas wilt and turn brown. They will remain on the tree long after all the other leaves have fallen. Remove all infected wood as soon as the disease is discovered.

Burn the wood immediately or double bag it and send it to the landfill.

To avoid the transfer of active fungus and bacteria, sterilize tools between cuts.

A one per cent bleach solution was once the solution of choice but research has found that Lysol works just as good and doesn’t damage the blades of the equipment.

Keep an eye out for pests in the trees and remove them as soon as they appear before they can spread.

Linda Tomlinson is a horticulturalist who lives near Rocky Mountain House. She can be reached at

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