Month: May 2016

There is an insect pest, in it’s larval stage, that causes extensive damage to Spruce trees in Edmonton. The Adult Yellow-headed Spruce Sawfly insect, is a small stingless wasp. The adult males and females look the same, in appearance:  yellow in colour with black markings on their heads.  This insect, generally produces one new generation per year.  The destructive larva are approximately 18mm long, with yellowish-brown heads and green bodies with 6 visible stripes that go down the length of their bodies.  Not to be confused with a “caterpillar”, the sawfly larva have  6 or more sets of pro-legs, which can be easily seen. A unique characteristic of these larva, are that when they are disturbed they will rear up the front part of their bodies, and release a green spruce- smelling fluid from their mouths.

The damage to spruce trees is primarily caused by the eating of the needles by the larva. Generally speaking, the larva will attack trees after the third season after planting, not earlier. The pest, usually gravitates to the upper part of the trees.  Cleanly removing the whole needle, they will stop feeding mid- summer and drop to the soil, to cocoon.  They pupate in late winter, and the adults emerge approximately the same time as the spruce bud swelling in the Spring.  The females, which fly to a host tree, will lay a single egg in a slit at the base of each needle, all her eggs are usually laid on a single branch sprig.

Be aware that repeated removal of the needles of your tree, can lead to tree demise. Regular monitoring by your tree care professional, will be crucial. This insect pest, is a strong defoliator in the Edmonton area, and  it’s  damage is very visible.  Often by the time its effects are seen, the insect has caused the majority of it’s damage for that season.

Contact your best certified arborist, in early Spring, to monitor and inspect your spruce trees for evidence of feeding larva.

The Yellow-Bellied Sap Sucker is the only bird in the Woodpecker Family that attacks specifically living trees, to get it’s food. The birds are known for attacking a large variety of tree species. In the urban landscape, many thin-barked trees are preferred and targeted, including Birch, Amur Cherry, Mountain Ash, and Scot’s Pine.

This bird is identifiable by it’s black crescent shape on it’s breast, pale yellow belly, white wing stripe and red crown on its head.  Although this bird does eat insects, it is better known for the tree damage that is evident, from it’s feeding. They will drill (peck) into the bark, to sap-level, and cause damage by creating rows of tightly lined holes, often in a grid pattern. Once they tap into the sapwood, they will use their long tongues to drink the tree fluid that oozes out.  If a tree has been visited by the Sap Sucker lightly, often the tree can make a full recovery.  However, when many rows of holes are around the branch or trunk, the tissue of this area of the tree may “girdle”, causing the restriction of the flow of nutrients and fluids.  Parts of the tree or the entire tree may decline or die.

The likelihood of a Yellow-Bellied Sap Sucker to visit your tree, is anyone’s guess.  As with all birds, they may pick your tree, as a nice one to visit.  However, as a deterrent, noisemakers in the tree or near the area, may be effective. Hanging shiny or reflective items that move, may also work. Lightly wrapping burlap or canvas around the visited area, is commonly recommended to discourage the bird’s return. Keep in mind, that the Yellow-Bellied Sapsucker is protected under the “Migratory Birds Convention Act”.  So, the bird may not be captured, injured or it’s eggs damaged or destroyed.

As always, it is recommended to maintain your tree’s health, as well as possible, and reduce other stress factors.   Your Edmonton Arborists can help to identify the visible damage as seen on the tree, and discuss with you any pruning or maintenance that your landscape trees may benefit from.