The Spruce spider mite attacks predominately white, Colorado and Blue Spruce. It attacks the Conifer species making Cedars, Fir trees, Juniper, Larch and Pine susceptible as well. It is difficult to identify the spider mite as they are most often tiny and invisible to the eye. Holding a sheet of white paper under a branch, while shaking the limb will often times dislodge the mites, making them visible.
The mite originate in an egg which lays dormant during the winter under the bark, buds or at the base of the needles. In the spring (May-June), these eggs hatch into oval shaped larvae with three legs. These larvae feed off the needles and begin to turn from a pinkish color to green. They produce high amounts of offspring in a short period of time.
Needles will have a molted appearance.
Needles turn yellow and brown, they fall off prematurely.
Mites also spin webbing around the needles; the webbing can have a greyish appearance.
High amounts of webbing on the tree is one of the final stages and indicates a high mite population.
Black knot fungus is a disease that afflicts cherry and plum trees. It is similar to a spore comparable to a mushroom. Like most fungus this disease spreads in warm wet weather. In advanced stages this fungus can be detrimental because as it grows it wraps around branches, cutting off circulation. Affected branches eventually die, and in extreme and untreated cases it can kill a tree.
In the early stages you will notice swollen lumps on branches.
Spores begin to release during the leafing/budding period in early spring.
In advanced stages the swelling explodes into clumps.
The clumps may be brown or black and be velvety or brittle.
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Fire blight is probably one of the most destructive diseases of fruit trees in Alberta. It is caused by a bacterium that enters fruit bearing trees through blossoms or tree wounds. The bacterium forms cankers that dispense the bacteria in the form of amber/brown secretions. These secretions are spread throughout a tree by rain, humidity, by birds and by insects. The disease develops best in warm, humid temperatures. You may see it occur erratically throughout a tree and it is unpredictable. Occurrences that become serious or infect the main limbs in a mature tree can result in serious structural damage and even death.
Wilted blossoms, or blossoms that turn brown in the spring.
Fruits that are young may appear to be covered in oil, and may ooze milky, tawny or clear fluid (it may also smell bad.)
Limbs begin to die (usually tips first) and appear to be charred by fire.
In the winter months you will notice the dead leaves and shrivelled berries cling to the branches.