Tree Disease and Insect Management
Tree Disease and Insect Management in Edmonton
KEEP YOUR TREES FREE FROM DISEASE AND INSECTS
Your trees can be at constant risk from disease and insect infestation. That is why it is essential to contact the tree care professionals from Arbor Man Tree Care as soon as possible if you think there are issues with your trees. You will find examples of common diseases and insects that can wreak havoc on your trees on this page.
Dibotryon morbosum or Apiosporina morbosa is a plant pathogen, which is the causal agent of black knot. It affects the cherry, plum, apricot and chokecherry trees of North America. 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.
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, and pruning is best done 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 it is a clean defoliator, leaving a few partial needles in its wake and feeds on new and old needles. Yellow-headed spruce sawfly will rarely be found on all spruce trees in a planting.
Options include: Handpicking, especially when numbers are small; High-pressure blast of water; Insecticidal soap; Ace-Jet systemic insecticide is useful for control of this pest.
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 foliage and some old foliage may be destroyed for several years. Buds and developing shoots may be killed in their formative stages. Complete tree mortality can occur following five to six years of severe infestation.
Ace-Jet systemic insecticide is useful for control of this pest.
POPLAR BORER AND POPLAR WILLOW 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 then 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. Willow is the preferred host of the Poplar Willow Borer (Cryptorhynchus lapathi), and poplar can also be affected (NOT Swedish Aspen). Poplar and Willow Borer typically attack stems that are between 1-4″ in width.
Very little research has been 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 typically 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 death of the tree. In later stages of infestation, the trunk will show D-shaped, rust-stained exit holes and may also have swollen extrusions under the bark where the tree tried to grow over larval galleries.
Ace-Jet systemic insecticide is useful for control of this pest. Treat Bronze Birch Borer with either TREE-äge or IMA-jet. The comparatively large vasculature in birch trees will readily move IMA-jet upward into the canopy. TREE-äge is more viscous and will take slightly longer to inject but will provide a more prolonged residual effect. TREE-äge and IMA-jet will eliminate the Bronze Birch Borer larvae inside the tree. Independent studies strongly recommend that treatments be applied early before an extensive disruption occurs to the vascular tissues. Arborjet recommends treatment when Bronze Birch Borer is detected in your area, but trees still appear healthy for best outcomes (dieback symptoms on infested trees should be <40%). Applications should be made in the spring, about 30 days before expected adult emergence; however, treatment may be applied during the growing season (May – September) to protect trees. Uptake of the formulation is fastest when trees are actively transpiring after they have developed a full canopy. Bronze Birch Borer treatment in the spring will prevent the adult beetles from feeding and laying eggs in the tree, whereas summer treatment will kill the larval stage of Bronze Birch Borer feeding under the bark. Make summer treatment applications in the morning when temperatures are moderate if the soil is dry, water trees before treatment. Injection in the fall (after leaves colour but before they fall) can protect the tree for the following season. This should be done every other year for ongoing protection.