Early detection key to protecting trees

Insects and diseases infect urban and rural forests.

Insects and diseases infect urban and rural forests.

Careful monitoring of the trees allows for early detection which increases the chances of the plant surviving and the less likelihood what the problem will spread.

Black knot is a fungus that infects many species of fruit bearing plants of the genus prunus.

In the last few years the fungus has been commonly found in May Day and Shubert chokecherry trees.

Around blossom time the fungus spores spread from one tree to the next in the wind and rain.

Fungus enters plants through openings in the bark or the flowers and lodges in new growth or last years growth.

The area will swell slightly and turn brown. By next spring the infected growth swells and becomes a velvety green. Once the spores are released and the knot will dry out and become black knots.

The knots or lumps are very noticeable at this time on year.

The best method is to remove all diseased growth cutting at least a half-inch (one-cm) below the knot. Burn the infected wood immediately or double bag it and put it in the garbage.

Bronze leaf disease has been moving across the Prairies and damaging or killing poplar trees. The first sign of the disease is the discolouring of leaf margins in June or July.

As the season progresses the fungi works it way up the leaf until the leaf is bronze, dark red or brown.

These leaves will stay on the plant long after others have fallen to the ground. The first leaves to become infected are usually in the crown or top of the tree.

As with the black knot, the best method is to prune out all diseased wood and dispose of it correctly.

Leaving it in the yard will allow the fungus to continue to spread.

Poplar trees, native or non-native, are susceptive to the poplar boer. The cycle starts with a beetle laying eggs in an opening in the bark that already exists or is made by the beetle.

When the larva hatches it starts boring tunnels inside the tree.

This continues until the larva forms a cocoon and hatches as an adult that leaves the tree to mate and start the process again. The complete life cycle takes two years.

Tunnels within the sap and heartwood of the tree cause it to weaken and become unstable. These insects are damaging the inside of the tree. Small slits where sap runs are an indication that the tree is infected.

Once the tree is removed the tunnels within the tree are easy to see.

The problem can be controlled by removing all infected trees and using an insecticide in the spring to reduce the number of beetles.

The numbers of forest tent caterpillar escalates and shrinks.

When their numbers are high they swarm and defoliate huge strands of trees during their larva stage which lasts four to six weeks.

Most healthy trees can survive losing and replacing their leaves for a season or two. When the outbreak continues for a longer period of time it becomes a problem and trees die.

Removing and destroying the tent like webs that hold the eggs in early fall helps keep the number of these insects in check.

The hungry larva can be sprayed with Bt but it isn’t practical when the caterpillars are so thick that they cover everything.

Taking time to look at the trees in the yard is time well spent. Catching problems when they are in the early stages can save the plants.

Linda Tomlinson is a horticulturalist that lives near Rocky Mountain House. She can be reached at www.igardencanada.com or your_garden@hotmail.com