Bugs attack plant roots, stems, leaves, flowers and fruit on plants. Soap and water offers a human-friendly alternative to pesticides. Insecticidal soap is mainly used to control soft-bodied arthropods like aphids, mealybugs, psyllids and spider mites. Larger bugs like boxelder bugs and Japanese beetles are also susceptible to soap. Soap has been used for over 200 years as bug control. Soap and water control does not have residual effects and it can damage some plants.
Separate your pest infested plant if possible. For houseplants, just move the plant pot into an area away from any other plant. For a single plant in the garden, place a bucket over it. This minimizes the infestation. For garden plants, you may not be able to isolate the infested plant.
Mix together 5 to 8 tbsp. of insecticidal soap in a gallon of water. This will create a 2 to 3 percent solution. Pour the mixture into a spray bottle.
Spray a small area of the infested plant two days before using the soap and water mixture all over the plant. This tests the plant for phytotoxicity, which is a reaction to the soap by the plant. Watch for browning in the area sprayed. If the area starts to turn colors and die, then you cannot treat it with soap and water.
Spray the plant with the soap mixture thoroughly in the early morning or late afternoon so the plant stays wet longer. Cover the pests by spraying under the leaves and in other protected areas. Watch for bugs hiding in curled leaves.
Rinse the plant off with clear water two hours after soap and water application. This will help minimize any damage to the plant. Repeat the soap and water application every four to seven days while the infestation lasts. Spider mites and scale crawlers take several repeated application to control.