The control of insect and tree disease pests on trees often involves tree spraying. Tree trunk injections or soil injections can be done to control some insect and disease pests of trees, but the most common method used is tree spraying. Many tree care companies that offer tree pruning or tree removal also offer tree spraying. The equipment used for tree spraying can be as small as a backpack sprayer all the way up to a 1000 gallon tank trunk. The equipment an arborist uses for tree spraying depends on the tree species, tree size, and the insect pest or tree disease pest the arborist is controlling.
Some tree species are highly targeted by insect pests or various tree diseases, while other landscape trees are relatively pest free. A local arborist, or local tree service, can be a valuable resource in determining what landscape trees will be prone to attack by insect pests or tree diseases.
Tree sprays fall into two broad categories: preventative tree sprays or curative tree sprays.
PREVENTATIVE TREE SPRAYS
An example of a preventative tree spray is when an arborist, or tree service, is attempting to stop damage from an insect pest or tree disease. This type of tree spray is applied just before the insect pest or tree disease is anticipated to be active. Applying the tree spray just before insect or disease activity means the insecticide or fungicide will be able to prevent or minimize insect or tree disease damage. If you are trying to stop a tree disease that affects tree leaves a preventative tree spray should be scheduled. Most insect pests can also be controlled with preventative tree sprays.
CURATIVE TREE SPRAYS
Curative tree sprays are done after the tree pest is already present. If an insect pest has already started feeding on your trees or shrubs a curative tree spray can stop the insect pest from causing too much damage. Because the populations of insect pests that feed on trees and shrubs can fluctuate from season to season it may not always be necessary to spray a tree or shrub every year. In other cases, tree or shrub damage will be almost certain if tree spraying isn’t done. This variability is usually due to the species of the trees and shrubs in your landscape. Your local arborist or tree service will be able to let you know what trees or shrubs in your landscape are commonly attacked by various insect pests or tree diseases.
Tree spray programs are also divided into two general categories: targeted tree sprays or periodic tree sprays.
TARGETED TREE SPRAYS
Targeted tree sprays are designed to control a particular insect or tree disease at a certain time of the season. When a targeted tree spray is scheduled only one tree, or tree species, in the landscape is treated by the tree service. An example of a targeted tree spray would be if the tree service sprayed just the crabapple trees in your landscape for Apple Scab disease. Tree disease control programs are often set up by a tree service as targeted sprays because the timing of the tree spray is critical to obtaining control of the tree disease.
PERIODIC TREE SPRAYS
Some tree service companies offer a tree spray program where the tree service visits your property every 4 – 6 weeks to inspect your landscape plantings. The arborist inspects your trees and sprays trees that have insect pests or trees the arborist suspects will be attacked by insect pests before the next visit.
HOW DO ARBORISTS KNOW WHEN TO SPRAY CERTAIN TREES
Arborists use two natural indicators to determine when various insect pests will become active: Growing Degree Days and Phenological Indicators. Insect activity is closely related to atmospheric temperatures. Calculating Growing Degree Days is done by using a mathematical formula to measure the amount of heat that accumulates above a base temperature in 24 hours. Certain insects are known to become active when the accumulation of Growing Degree Days reaches a certain range. Phenological Indicators use the bloom period of flowering plants as an indicator of insect activity. Both of these methods give arborists and tree service companies a better idea of when insect pests will become active than just using a calendar to schedule tree sprays.