- 1). Put on disposable gloves, safety glasses and a dust mask. Fill a handheld pump sprayer with an insecticide labeled for use on water bugs or roaches. Look for products that contain one of the following active ingredients hydramethylnon, fipronil, boric acid or sulfluramid. Screw the top on securely then raise and lower the top handle until you feel resistance, which means it is properly pressurized.
- 2). Spray the insecticidal product around the base of water oak tree then extend the spray outward at least 6 feet from the trunk. Finally, spray the trunk with insecticide up to 12 inches from the ground.
- 3). Reapply the insecticide once per month until you no longer see any water bugs around the tree.