Quote:
Originally Posted by modenacart
Just spray with soap water everyday for a couple of weeks. Soap kills them by softening their exoskeleton.
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Soap has no effect on exoskeleton of living arthropods. The outer surface of arthropods' respiratory systems is hydrophobic - taking advantage of surface tension of plain water to keep it out of arthropod's body. Adding soap or detergent reduces surface tension drastically, allowing it to bypass the hydrophobic surface, enter the respiratory system and drown the arthropod.
Soapy water is effective on contact with respiratory surfaces. It has no residual effect. Arthropods can escape by hiding in soil or on protected areas of plant. Soapy water can effect the waxy layer (also hydrophobic) on the outer surfaces of stems and leaves, causing discoloration.