Broad-spectrum insecticides or pesticides are formulated to kill many kinds of pests with the use of one product. Concentrated products are much less expensive to use than non-concentrated products and can be applied with a compression garden sprayer. Spray tree branches with an insecticide or pesticide when little wind is present; otherwise, the spray will drift. Wear the correct protective gear to prevent the product from getting on your skin and causing irritation.
Put on a long-sleeved shirt, long pants, socks, enclosed-toe shoes, safety glasses and waterproof gloves. Wear a hardhat or other protective headgear that is waterproof. Pesticide and insecticide chemicals cause irritation to skin and mucous membranes. So all areas of your body should be protected from them.
Open the lid of a compression garden sprayer counterclockwise and remove it. Add water from a garden hose to the sprayer tank's one-half full mark.
Add pesticide or insecticide concentrate to the sprayer tank by using a plastic measuring spoon and by following the amount to use listed on the pesticide's or insecticide's label directions.
Pick up the sprayer tank, and swirl it in a circle while filling the tank to its full mark with water from the garden hose.
Screw the lid clockwise onto the garden sprayer. Pump the handle on top of the sprayer. Pumping the handle adds air pressure to the sprayer's contents.
Walk to the tree that needs the pesticide or insecticide treatment. Stand just beyond the tree's drip line to avoid chemical runoff onto yourself. The drip line is below the tips of the tree's outermost branches. Squeeze the application wand on the sprayer to dispense the pesticide.
Spray the tree's canopy from its highest point, including all branches and leaves, to the areas directly in front of you. Apply the spray to all sides of branches and leaves.
Move to one side, and spray the tree in the same manner as before to wet all its surfaces thoroughly with the spray. Continue to move and spray until you are standing at the point where you started spraying the tree. The starting point of coverage should be visible by the spray's moisture on branches and leaves.
Walk around the tree slowly as you spray the tree's entire trunk, starting at the top from which the lowest branches attach and working down to the ground.