Insects can kill a tree if you don't take steps to counteract the problem. Tree spraying can be an effective means for controlling pest problems, as long as it is done correctly.
Know the Problem
You can't spray for pests until you know what type of pest is harming your tree. Although so-called "broad spectrum" sprays are out there, they will destroy the beneficial insects as well as the bad, Further, without knowing what insect is causing the problem, it's impossible to determine the right time to spray the tree to have the most effect. A tree service can often identify insect type just from seeing the damage, but if not, a bit of sleuthing will likely turn up the culprit.
Determine It's Severity
Spraying should only be used if absolutely necessary simply because it can harm beneficial insects or leech pesticides into the surrounding landscape. If the insect pest that is attacking your tree is only going to cause cosmetic damage, such as a few chewed leaves, then it may be better to skip the spray. On the other hand, if extensive damage is possible which may weaken the tree, or if the insect could move to more susceptible plants, then the problem is severe enough to warrant spraying.
Decide The Type of Spray
When it comes to spraying for insects you need to decide between two categories of treatments. Dormant oil sprays coat the insects and smother them. These sprays do contain fewer toxins than a pesticide spray, but they can damage conifers and some young plants because they clog the pores the needles or leaves. It can also be difficult to apply dormant oil to larger trees effectively. Pesticide sprays are targeted to a specific pest to help minimize damage to beneficial insects, but there may be some leaching of the pesticide into the environment.
Choose the Right Time
Timing is everything when using an insect control spray on your trees. First, you must time the spray to coincide with the proper lifecycle of the pest. Many tree pests live under the bark during their larval stage, if they are even on the tree at all at this point. They may only emerge to feed at maturity. Other pests do the most harm in the larval stage, but the only way to destroy them before they burrow into the wood is to spray when the parents are mating but before they lay eggs on the tree. Your tree service will identify the insect and determine the best time in the pests' lifecycle to apply a spray.
Contact a tree service in your area for more help.