BLACK KNOT

Dibotryon Morbosum or Apiosporina Morbosa is a plant pathogen, the causal agent of the Black Knot. It affects North America’s cherry, plum, apricot and chokecherry trees. Most commonly infecting chokecherry (Mayday and Shubert) in Alberta. The disease produces rough, black areas that encircle and kill the infested parts and provide insects’ habitat. Black Knot occurs only on the wood parts of trees, primarily on twigs and branches but can spread to larger limbs and even the trunk. Olive-green swellings from the disease are visible in the late spring, but it spreads and matures typically by autumn.

Recommended Treatment

Prune out infected parts 6 to 8 inches back from an infection, making sure not to cut through infected parts and spread the disease. We recommend regular disinfection of pruning tools, which is best when the tree is dormant.

YELLOW HEADED SPRUCE SAWFLY

Yellow-Headed Spruce Sawfly- (Pikonema Alaskensis Rohwer) can cause severe economic and aesthetic loss to ornamental and commercially grown spruce. The needles’ feeding destruction can reduce plant growth and vigour up to two years after the damage occurs. The yellow-headed spruce sawfly “worm” is commonly misidentified as the spruce budworm. Misidentification is most likely because both insects are spring defoliators. But this is where the similarity ends. The yellow-headed spruce sawfly is a stingless wasp and a clean defoliator, leaving few partial needles in its wake and feeding on new and old needles. Yellow-headed spruce sawflies rarely get found on all spruce trees in a planting.

Recommended Treatment

Options include:

• Handpicking, especially when numbers are small
• A high-pressure blast of water
• Insecticidal soap

Arbor Man Tree Care can inject a chemical called TreeAzin, into the trunk to help control this insect. This must be done early spring to ensure the chemical moves up with the spring flush. After that the chemical does not move up the trunk as well.

SPRUCE BUDWORM

Spruce Budworm – being a messy eater, needles are seldom entirely consumed by the larvae but are often clipped at the base and webbed together. These dead needles persist on the trees for a few weeks giving trees a scorched appearance in mid-summer. When populations are low and moderate, partial loss of new foliage occurs, particularly in the tree’s upper portion. During severe persistent infestations, all the new and some old foliage may be destroyed for several years. In their formative stages, Buds and developing shoots may get killed. Complete tree mortality can occur following five to six years of severe infestation.

POPLAR BORER

The poplar borer (Saperda Calcarata) is a common insect in urban and rural Alberta. Adults are large (20-30mm), long-horned, light blue/gray beetles with orange markings. Larvae are legless, white, and 30mm long. The most visible sign is the damage they cause to poplar and aspen trees – boring large holes that then weep sap that stain the bark a dark brown. The larvae remain inside the trees feeding for two to five years before pupating and emerging as adults to mate and lay eggs. High populations of this insect may significantly weaken or stress trees, mainly if they are already under drought stress. Unlike other long-horned beetles, which only attack stressed trees, the poplar borer frequently attacks healthy, vigorous trees. Poplar and Willow Borer typically attack stems that are between 1-4″ in width.

Recommended Treatment
There has been very little research conducted on the control of this pest. Most studies have focused on spraying insecticide into exit holes to control larvae and spraying trees’ bark to prevent adults from laying eggs.

BRONZE BIRCH BORER

BBB (Bronze Birch Borer) has become an epidemic in Alberta. The adult is a copper/bronze-coloured slender beetle. The larvae, which do the damage, are unseen, feeding on the bark’s vascular tissue. The Bronze Birch Borer attacks trees that are already stressed or in decline. A birch infested with Bronze Birch Borer will start showing dieback in the crown, increasing in severity as the infestation continues, often leading to the tree’s death. In later stages of infestation, the trunk will show D-shaped, rust-stained exit holes. It may also have swollen extrusions under the bark where the tree tried to grow over larval galleries.