Insects
Preventing and controlling insect damage to trees often requires the use of insecticides. Concerned with the overuse of insecticides, we use the most modern treatment methods and rely on plant health care practices to increase tree immunity whenever possible.
Emerald Ash Borer
Emerald Ash Borer is still our greatest concern in Norther Colorado. It has a foothold in almost every town and city here. Unlike many insects, Emerald Ash Borer (EAB) will attack any ash tree regardless of health or age and infestation leads to death of the tree. If you want to keep your ash trees they should be treated. There are many insecticides that can be used to treat EAB but in almost every situation one insecticide is favored, Emamectin Benzoate. It has a higher efficacy then other insecticides, more persistent, and the most cost effective. It can be applied throughout the growing season. Early spring applications will also control adult EAB as they feed upon leaves but only for the year of treatment. This can be advantageous when fighting concentrated populations of EAB as a community. However late season applications may be recommended if a tree may already be infected or under high pressure. Trees may not show signs of infestation for one season after actually being infected by EAB.
Three year treatment
Although it is commonly sold as a two year treatment there are multiple studies showing three year treatments provide effective control.
https://auf.isa-arbor.com/content/48/3/165
Last link is a simple summarization of critical points on EAB.
https://www.bfw.gv.at/wp-content/uploads/12_McCullough_1.pdf
IPS Engraver Beetle
IPS Engraver Beetle has become much more common over the past several years due to the stress put on trees from the drought. Attacking spruce trees, it initially shows as die back at the top of the tree and quickly moves down the tree causing mortality in as short as one growing season. Usually only mature trees are attacked but small immature trees have been affected recently. Consistent watering is very important in preventing infestation but in areas where neighboring trees have already been infested treatment is highly recommended.
Oystershell Scale
Oystershell Scale can be found on many trees and although it is not usually life threatening, it is a good indicator that your tree needs help. Appearing as small bumps on the trunk and twigs and most commonly found on Aspen trees. Small infestations can be simply brushed off but the tree should be inspected to see if there are any environmental stressors affecting the tree. Large infestations should be treated.