Hopefully your trees and shrubs will never be attacked by beetles. They bore into the plant, destroying the nutrient transport system and weakening the overall health. If the infestation is serious enough, death may occur. They are very hard to control, but here are some ways to get rid of beetles:
Choose Trees and Shrubs Wisely and Keep Them Healthy
This may seem very obvious, but it's best if you take steps to try not to have a beetle infestation at all. This begins by choosing trees and shrubs that are adapted to growing in your area; species that are poorly adapted will struggle and have health issues. Make sure it is planted properly and watered well to help limit the amount of stress the tree goes through. If you keep the plant healthy, it has a much better chance of not being attacked, and a better chance of surviving if it is.
Keep the tree or shrub free of cuts and breaks. Do not do your pruning when beetles are known to be in the area. Don't leave newly cut firewood nearby, as this will provide a place for the beetles to breed.
Different beetles attack different kinds of trees and shrubs, so don't plant the kinds affected if there have been known infestations in the area. You can also try species known to have some resistance.
Hire a Licensed Pesticide Applicator to Apply Appropriate Pesticides
It is difficult to control beetles using chemical means unless the beetle attacks are detected very early. The pesticides used are also very expensive and not usually available to homeowners. However, if you have valuable trees that you would like to try to save, call in a licensed pesticide applicator. They may be able to save trees by spraying the trunks when the adults are flying.
Trees and shrubs that were attacked in the past but no longer have beetles should not be sprayed. Neither should you spray species that are not affected by the type of beetle present. Trees that are highly infested cannot be saved by pesticides.
Prune Away Affected Branches
If the beetle problem is noticed early enough, you can prune off any branches that have been attacked. However, you should be careful when doing this, as new pruning wounds may attract more beetles. Learn the months when the adult beetles are flying and try to avoid pruning during those times.
Cut Down Affected Trees and Shrubs
Sadly, cutting down the affected trees or shrubs is the only surefire way of controlling beetles in most cases. Usually by the time the problem is noticed, the infestation is too widespread to be controlled. Pesticides are not able to wipe out large beetle populations, nor pruning if the whole plant is affected.
If you have many susceptible trees together, thinning them out can help improve the chances of the remaining trees' survival.
Cut down the affected tree or shrub entirely and destroy the wood. The pieces should be chipped or burned to destroy any beetle larvae. Be sure to move it far away from your remaining trees and shrubs or the beetles may find a new home.