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Branch damage:
Have winter storms cracked branches? While trees are leafless, check for cracks, ripped branches, or branches crossing and rubbing others. Remove these now with sharp pruners or a good saw. Don't leave jagged bark or pruning cut stubs. Dealing with damaged branches is even more important than shaping the tree or shrub for aesthetics.
Bark cracks:
Winter temperature extremes will sometimes cause longitudinal bark splits or cracks. This often happens on the south facing side of newly-installed trees. Bark splits commonly occur on maples, apples, beeches, walnut, and willow as well as other trees. If the newly-planted tree is protected by shrubbery or other trees, damage will be lessened. Solitary trees with full sun exposure are most susceptible. Using tree wrap around newly-planted trunks for the first few years of life helps to protect trees in vulnerable situations.
Trees that do develop splits will adjust to them as to other wounds; callus tissue may gradually form, and the plant may stabilize as the split heals. Adjustment depends on severity and how well established the tree is. Be sure to watch such trees through the summer and don't allow them to endure drought while they are recovering.
Normal bark may also give evidence of shedding or splitting:
Some trees naturally have shaggy or "peeling" bark, with furrows as the trees grow. This isn't damage and shouldn't be confused with the deep, single splits that weather may cause. Trees with rough or peeling bark, particularly as the trees grow older, include mulberry (Morus rubra), Tibetan cherry (Prunus serrula), black walnut (Juglans nigra), and London plane (Plantanus x hybrida). The bark effects contribute to the beauty of many trees in winter.
Problems on blue spruce and other spruce:
Blue spruce trees (Picea pungens 'Glauca') and all other spruce grown in western Washington suffer from insect problems. The most common difficulty is spruce aphid (Elatobium abietinum).
Spruces, including Englemann spruce (Picea engelmannii) and dwarf Alberta spruce (Picea glauca 'Conica') are frequently planted in landscapes. The trees, when healthy, offer crisp "Christmas-tree" shapes with vibrant green or blue-green needles. Many of these spruces thrive in cold winter climates, and are classic parts of Rocky Mountain and Appalachian flora.
Spruce aphids do their nasty work in mid-winter, when the small, almost invisible, green aphids feed on the needles. If you have spruce trees, check the growth from January through late February. A good way to look for spruce aphids is to hold a piece of white paper under the branch and tap it. The insects will fall off onto the paper like small greenish specks, moving.
If a determined gardener wishes to grow spruce and wants to get some control for the spruce aphid problem, the WSU recommendation is to spray now during winter when the insects are active. The least-toxic materials registered for the problem are horticultural oils or insecticidal soaps. Be sure to get thorough coverage of all needles, and apply on a dry day. It's impossible to treat this problem during summer when you may see needles dropping off the spruce. Also, be aware that horticultural oils will discolor the blue needles of Colorado blue spruce, turning them a muddy green.
Peach leaf curl:
Fruiting peaches (Prunus persica) open their buds very early. If you've been troubled with peach leaf curl, a fungus problem that attacks the leaves and causes the plant to defoliate, it's important to apply a protective fungicide now just before the buds begin to open. Spores overwinter on the bark and twigs, and can infect the new leaves. Once the outer layers begin to open, the fungus can enter the bloom. WSU recommends spraying with lime sulfur or a copper spray west of the mountains. Do this now to protect the trees.
The peach named 'Frost' resists peach leaf curl after the tree reaches 4 to 5 years old, but is susceptible in the first years of its life.
Hortsense: Managing plant problems with Integrated Pest Management
