Spider mites can be found in most species of spruce but are predominately found on Colorado or White spruce. Spruce spider mites are tiny and very difficult to see. They are approximately .5 millimeters and are a dark green to dark brown in colouration. The best method to find out if your spruce tree may have mites is to place a white piece of paper under a branch and shake it repeatedly. Fold the paper in half, if red smears appear after opening the paper, chances are you have spider mites living in your trees. Ensure you check your trees on a regular basis as mite populations can grow quite rapidly.
By using their sucking mouth- parts the spider mites pierce the needle and extract sap from within. This feeding causes the needles to take on a bleached look to them. If the population is large enough the feeding can cause the needles to become a yellow to brownish colour. These needles eventually dry out and fall off. Spider mites begin feeding on the lower branches of the tree, feeding from the inner needles outward. They use a silk webbing throughout the area they are feeding on. Most trees are able to withstand an infestation, but a newly planted tree or one that is under stress from other factors is more likely to be injured by this pest.
As with many tree pests’ weather such as wind rain and temperature are a great help in controlling an infestation. You may also be able to achieve acceptable control by using your garden hose to spray down any trees that may be under attack. Looks for the silk webbing the mites create which is found on the underside of the lower branches. If you are using a chemical control it is advisable to hire a reputable tree service to perform this task. The reason for this is that any insecticides used must be applied at high pressure to ensure the chemical reaches the inner branches of the tree. Most garden hoses will not achieve the type of pressure needed to achieve good control.