A tree in trouble due to disease or insect infestation can be difficult to treat with pesticides and fungicides, because conventional garden sprayers may be limited to spraying only a few feet. Power sprayers may be able to deliver a thorough spray to the foliage of trees more than 20 feet tall, but might not be the best tool to use.
Achieving Maximum Height
Using a power washer spray at full force may injure or even shred the foliage near the top of the tree. Power sprayers rated from around 700 psi to more than 3,000 psi are available for home use, but may be set to spray at much lower, gentler settings. Try beginning at the lowest psi setting with the nozzle set to deliver a wider rather than more focused spray, then adjusting as needed to spray the tree without harming the foliage.
What to Spray
Spraying chemicals into treetops can be dangerous, because droplets will almost certainly rain down on the operator. Gloves, protective eyewear and other gear are essential, but still may not protect you completely. In addition, you also run a greater risk of overspraying the tree so that chemicals fall onto nearby vegetation that may be harmed or killed. If the tree is suffering from a minor infestation of insects such as aphids or whiteflies, spraying the tree with plain water using a power washer can be effective. The strong spray will wash the insects off the foliage and may also wash away sooty mold that grows on the honeydew deposits these sap-sucking insects excrete.
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