1) Spruce turning brown
For older spruce there may be a combination of several factors including; natural needle drop, age, weed competition, close spacing, drought, shading, competition from other trees and/or disease (cytospora canker).With younger spruce trees the reasons for browning include herbicide damage, salinity, insects (spruce spider mite, yellow-headed spruce sawfly, spruce budworm),needle cast disease, septic pump-out, moving, trenching and winter browning.
2) Spider mites on spruce
By mid-summer you notice a brown to grayish discoloration towards the inside of the tree. Characteristically fine webbing is noticeable around the twig and half way up the needles. If webbing is seen on the outside portion of the needles it is probably ordinary spiders, which are beneficial. Registered control products include malathion and dicofol (Rates on label).
3) Winter browning of coniferous trees
This is generally more of a problem with youngconifers. The brownish needle discoloration often occurs on the west and south sides of the tree, (south - sun reflection from snow, west - desiccation from prevailing winds). The damage occurs in early spring when the ground is still frozen and the air temperature is above freezing. Damage in some years is much worse than others. To reduce damage, water the conifers well in late fall and apply an anti-desiccant (available at garden centers) just before freeze-up.
4) Herbicide damage on spruce
Spruce trees are often damaged when people use dicamba based herbicides (Killex, Banvel, Dyvel, Par 3, Premium 3-way, Rustler, Target) to control dandelions in their lawns. Unfotunately while these herbicides effectively control dandelions homeowners are accidentally harming or killing their conifers. The conifers are normally not damaged by drift of the product but are harmed when dicamba is taken up by the roots. Dicamba products are very persistent in the soil rooting zone and shallow spruce tree roots can extend far in the lawn area.
5) Top dieback of hybrid poplars
This can be attributed to several causes; severe drought, canker disease, cold hardiness, frost injury and borers (carpenterworm and poplar borer). Choosing hardy and disease resistant poplars is the best strategy to avoid top dieback.
6) Plant bugs on green ash
The ash plant bug causes a stippling effect on the leaves of green ash. This pest is particularly a problem on young ash trees less than fifteen years of age. Heavy infestations can result in severe defoliation or even death of young trees. Registered control products include carbary. (Rates on label).
7) Sawfly on spruce
Damage by the yellow-headed spruce sawfly occurs in late June to early July. Larvae are green in color with a yellow to tan coloured head and about 2.5cm (1 inch) in length. The damage is most noticeable on new growth near the top of the tree. Registered control products include acephate, malathion and permethrin (Rates on label).
8) Tent-forming caterpillars on deciduous trees
There are three tent-forming caterpillars found in the prairies: Prairie tent caterpillar, ugly nest caterpillar and fall webworm. On young trees these insects can cause severe defoliation, but on older established trees the damage mainly impacts appearance rather than health. Numerous Registered control products include: carbaryl, malathion, diazinon and Bacillus thuringiensis (Rates on label).
There are many species of aphids attacking nearly all species of plants. Aphids can be found on the leaves, stem, twigs or roots of plants. They are small, soft bodied, pear shaped insects that vary in color. Aphids cause damage by sucking the sap from the plant with their piercing mouth parts. There are numerous products available for control of aphids.
10) Flooded trees
Trees react to wet conditions in different ways depending on the length of time the soil remained flooded, how often and when flooding occurred and how old and how healthy the tree is. Trees that have experienced flooding can exhibit damage symptoms for several years following the event. Their vigour and structural stability will be weak, and they will be vulnerable to attacks by disease-causing fungi and insects that invade weakened or stressed trees. There is no rescue treatment for severely injured trees. The best you can do to help your trees recover is to follow proper tree-maintenance practices, providing the best conditions for growth and limit additional stresses.